Williams WPC
Click to go back to the Williams solid state repair guides index.
1 Introduction
This guide covers Williams WPC-089, WPC-S, and WPC-95 games. Collectively, they are referred to as WPC games.
2 Game List
2.1 WPC (WPC-089) CPU
2.1.1 WPC (Alphanumeric)
2.1.2 WPC (Dot Matrix)
2.1.3 WPC FlipTronics I & II
- The Addams Family / Addams Family Gold (the only Fliptronics I games)
- The Getaway: High Speed II
- Black Rose
- Fish Tales
- Doctor Who
- Creature from the Black Lagoon
- White Water
- Bram Stoker's Dracula
- Twilight Zone
2.1.4 WPC DCS Sound
- Indiana Jones: The Pinball Adventure
- Judge Dredd
- Star Trek: The Next Generation
- Popeye Saves The Earth
- Demolition Man
2.2 WPC-S with DCS Sound
- World Cup Soccer
- The Flintstones
- Corvette
- Red & Ted Road Show
- The Shadow
- Dirty Harry
- Theatre of Magic
- No Fear: Dangerous Sports
- Indianapolis 500
- Johnny Mnemonic
- Jack*Bot
- WHO Dunnit
2.3 WPC-95 CPU
- Congo
- Attack from Mars
- Safe Cracker
- Tales of the Arabian Nights
- Scared Stiff
- Junk Yard
- NBA Fastbreak
- Medieval Madness
- Cirqus Voltaire
- No Good Gofers
- The Champion Pub
- Monster Bash
- Cactus Canyon
3 Game List Chart
3.1 WPC-89 & WPC-S
| Game | WPC System | MPU | Driver Board | Display Driver | Display | Sound | Flipper | Transformer | Additional Boards | Notes
|
|---|---|---|---|---|---|---|---|---|---|---|
| Dr. Dude | WPC-89 Alphanumeric / System 11 | WPC-89 (A-12742) | A-12697-1 | A-12739-1 | Alphanumeric, dual display (A-12793) | D-11581-2016 with a special power supply board (A-13502) | N/A | 5610-12718-00 (WPC) or 5610-12136-00 (System 11)? | Sound overlay board (A-13502) | Only about 100 Dr. Dude sample games use the WPC boardset. They included a special power supply board (A-13502) to accommodate the System 11 sound board (D-11581), and also includes the System 11 interconnect board (D-12313-2016). The bulk of the production run used the System 11C boardset. |
| Funhouse | WPC-89 Alphanumeric | WPC-89 (A-12742) | A-12697-1 | A-12739-1 | Alphanumeric, dual display (A-12793) | A-12738-50003 | N/A | 5610-12718-00 | Early FH games had a System 11 sound board (D-11581 / A-13971) with a special power supply board (A-13502) and a 5610-12425-00 transformer. Later games used the WPC A-12738 sound board. Funhouse Manual Addendum | |
| Harley-Davidson | WPC-89 Alphanumeric | WPC-89 (A-12742) | A-12697-1 | A-12739-1 | Alphanumeric, single display (A-12794) | A-12738-20001 | N/A | 5610-12718-00 | ||
| The Machine: Bride of Pin*Bot | WPC-89 Alphanumeric | WPC-89 (A-12742) | A-12697-1 | A-12739-1 | Alphanumeric, dual display (A-12793) | A-12738-50002 | N/A | 5610-12718-00 | ||
| Slugfest | WPC-89 Dot Matrix | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-60001 | N/A | 5610-12835-00 | Pitch & Bat game. | |
| Gilligan's Island | WPC-89 Dot Matrix | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-20003 | N/A | 5610-12835-00 | ||
| Terminator 2: Judgement Day | WPC-89 Dot Matrix | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50013 | N/A | 5610-12835-00 | ||
| Hurricane | WPC-89 Dot Matrix | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50012 | N/A | 5610-12835-00 | ||
| Party Zone | WPC-89 Dot Matrix / WPC-89 Fliptronic I | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-20004 | N/A | 5610-12835-00 | Some later PZ games started transitioning over to use the Fliptronic I board (A-15028). Different game ROMs are used depending upon if the PZ uses solid state flippers or fliptronic/standard flippers. | |
| Hot Shot | WPC-89 Dot Matrix | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50017 | N/A | 5610-12835-00 | Redemption game. | |
| The Addams Family | WPC-89 Fliptronic I | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-20017 | A-15028 | 5610-12835-00 | Extra flipper power supply (A-15416) | |
| The Getaway: High Speed II | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50004 | A-15472 | 5610-12835-00 | ||
| Black Rose | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-20013 | A-15472 | 5610-12835-00 | ||
| Doctor Who | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-20006 | A-15472 | 5610-12835-00 | ||
| Fish Tales | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50005 | A-15472 | 5610-12835-00 | ||
| Creature from the Black Lagoon | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-20018 | A-15472 | 5610-12835-00 | ||
| White Water | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50018 | A-15472 | 5610-12835-00 | ||
| Bram Stoker's Dracula | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-12738-50001 | A-15472 | 5610-12835-00 | ||
| Twilight Zone | WPC-89 Fliptronic II | WPC-89 (A-12742) | A-12697-1 or A-12697-3 | A-14039 | DMD | A-12738-50020 | A-15472 | 5610-12835-00 | Auxiliary 8-Driver PCB (A-16100) | Mid-way through TZ's production run, the A-12697-1 driver board starting being replaced with A-12697-3. At some point during production, a coin door interlock switch was added in order to cut high voltage 20VDC/50VDC power as a safety measure when the coin door was opened; this was included in all WPC titles from this point forward. |
| Indiana Jones: The Pinball Adventure | WPC-DCS | WPC-89 (A-12742) | A-12697-3 | A-14039 | DMD | A-16917-50017 | A-15472-1 | 5610-13491-00 | Auxiliary 8-Driver PCB (A-16100) | |
| Judge Dredd | WPC-DCS | WPC-89 (A-12742) | A-12697-3 | A-14039 | DMD | A-16917-20020 | A-15472-1 | 5610-13491-00 | ||
| Star Trek: The Next Generation | WPC-DCS | WPC-89 (A-12742) | A-12697-1 | A-14039 | DMD | A-16917-50023 | A-15472-1 | 5610-13491-00 | Auxiliary 8-Driver PCB (A-16100) | Driver board was changed to A-12697-1. |
| Demolition Man | WPC-DCS | WPC-89 (A-12742) | A-12697-3 | A-14039 | DMD | A-16917-50028 | A-15472-1 | 5610-13953-00 | Auxiliary 8-Driver PCB (A-16100) | A few prototype games used a WPC-S MPU, which uses a different ROM in order to work with the WPC-S security PIC. The standard ROM for WPC-89 boards will not work on the WPC-S board, but a WPC-89 MPU can be swapped in to replace the WPC-S MPU. All the sample and production games used a WPC-89 MPU. |
| Popeye Saves The Earth | WPC-DCS | WPC-89 (A-12742) | A-12697-3 | A-14039 | DMD | A-16917-50022 | A-15472-1 | 5610-13491-00 | ||
| World Cup Soccer | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039 | DMD | A-16917-50031 | A-15472-1 | 5610-13953-00 | ||
| The Flintstones | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50029 | A-15472-1 | 5610-13953-00 | Some revisions were made on the A-14039.1 DMD driver board, but it is interchangeable with A-14039. | |
| Corvette | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50036 | A-15472-1 | 5610-13953-00 | Auxiliary 8-Driver PCB (A-16100) | |
| Red & Ted's Road Show | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50024 | A-15472-1 | 5610-13953-00 | Auxiliary 8-Driver PCB (A-16100) | The transformer was moved to the rear of the cabinet starting with this game. |
| The Shadow | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50032 | A-15472-1 | 5610-13953-00 | ||
| Dirty Harry | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50030 | A-15472-1 | 5610-13953-00 | ||
| Theatre of Magic | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50039 | A-15472-1 | 5610-14515-00 | ||
| No Fear: Dangerous Sports | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50025 | A-15472-1 | 5610-14515-00 | ||
| Indianapolis 500 | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50026 | A-15472-1 | 5610-14515-00 | ||
| Johnny Mnemonic | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50042 | A-15472-1 | 5610-14515-00 | ||
| WHO Dunnit | WPC-S | WPC-S (A-17651) | A-12697-4 | A-14039.1 | DMD | A-16917-50044 | A-15472-1 | 5610-14515-00 | This was the only game to use a A-12697-4 driver board. | |
| Jack*Bot | WPC-S | WPC-S (A-17651) | A-12697-3 | A-14039.1 | DMD | A-16917-50051 | A-15472-1 | 5610-14515-00 |
3.2 WPC-95
| Game | WPC System | MPU | Driver Board | AV Board | Display | Transformer | Additional Boards | Notes |
|---|---|---|---|---|---|---|---|---|
| Congo | WPC-95 | WPC-95 (A-20119) | A-20028 | A-20516 | DMD | 5610-14515-00 | The first WPC-95 game. The A-20516 AV Board drives both sound and the DMD. The A-20028 driver board included flipper power circuits, eliminating the need for a separate fliptronic board. | |
| Attack from Mars | WPC-95 | WPC-95 (A-20119) | A-20028 | A-20516 | DMD | 5610-14515-00 | ||
| Safe Cracker | WPC-95 | WPC-95 (A-20119) | A-20028 | A-20516 | DMD | 5610-14515-00 | ||
| Ticket Tac Toe | WPC-95 | WPC-95 (A-20119) | A-20028 | A-20516 | DMD | ? | Redemption game (with flippers). | |
| Tales of the Arabian Nights | WPC-95 | WPC-95 (A-20119) | A-20028 | A-20516 | DMD | 5610-14515-00 | ||
| Scared Stiff | WPC-95 | WPC-95 (A-20119 or A-21377) | A-20028 | A-20516 | DMD | 5610-14515-00 | The first appearance of a revision to the MPU. A-20119 and A-21377 can be used interchangeably in any WPC-95 games. | |
| Junk Yard | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-00 | ||
| NBA Fastbreak | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-01 | ||
| Medieval Madness | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-01 | ||
| Cirqus Voltaire | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-00 | DMD is mounted on the playfield, rather than in the backbox. | |
| No Good Gofers | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-00 | ||
| The Champion Pub | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-00 | ||
| Monster Bash | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-01 | ||
| Cactus Canyon | WPC-95 | WPC-95 (A-21377) | A-20028 | A-20516 | DMD | 5610-14515-01 |
4 Recommended Documentation
4.1 Manuals & Schematics
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's game manual is a handy resource to have for general game operation, game settings & diagnostics, switch & lamp matrices, fuse lists, circuit boards and parts, playfield assemblies, some basic schematics, and wiring diagrams.
Be aware that although rare, some factory documentation contains errors in schematics, wiring, switch/lamp matrices, and solenoid assignments.
Some games have information split between two manuals: a game manual (for general game operation) and an operations guide (for more technical information).
| Guide | Version | Cover | Source | Notes |
|---|---|---|---|---|
| Pinball Safety Manual | 16-10371, January 1, 1997 | Manual contains multiple languages. |
4.2 Theory of Operation & Schematics
Details for board and cabinet schematics and theory of operation guides for WPC games can be found in separate documents. There are several versions of each generation. Some copies can be found on Planetary Pinball.
| Guide | Version | Cover | Source | Notes |
|---|---|---|---|---|
| WPC Theory of Operation and Schematics Manual | 16-9289, October 1991 | Viewer for Guide Viewer for Schematics |
||
| WPC Schematic Manual | 16-9473 (undated) | Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.
| ||
| WPC Schematic Manual | 16-9473-1, May 17, 1993 | Viewer |
Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.
| |
| WPC Schematic Manual | 16-9473-2, April 25, 1994 | Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.
| ||
| WPC Schematic Manual | 16-9834, June 1994 |
| ||
| WPC Schematic Manual | 16-9834.2, January 1995 | Viewer | ||
| WPC-S (Security) Schematic Manual | ||||
| WPC-95 Schematic Manual | 16-10159.2, March 1996 | |||
| WPC-95 Schematic Manual | 16-10159.3, July 1997 |
4.3 Parts Catalogs
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Parts catalogs also had supplementary updates to add and replace pages as newer games were released after the initial release of the catalogs.
Online copies of Bally & Williams parts catalogs can be found on Planetary Pinball.
| Manufacturer | Catalog | Version | Cover | Source | Games | Notes |
|---|---|---|---|---|---|---|
| Williams | Blue Parts Catalog (1984-1987) | 16-9064 | Comet, F-14 Tomcat, Grand Lizard, High Speed, Millionaire, Pin Bot, Road Kings, Sorcerer, Space Shuttle | This was an early version of the blue parts catalog, and only included 9 pinball titles (and 3 shuffle alley titles). The pages of this catalog were printed on white paper. Additional titles were later included in a "parts catalog supplement" packet (16-9064-A) with blue-colored pages, which added and replaced pages for this earlier version of the parts catalog. | ||
| Williams | Blue Parts Catalog (Supplementary Catalog) (1987-1988) | 16-9064-A | Banzai Run, Big Guns, Cyclone, Fire!, Space Station, Swords of Fury, Taxi | This "parts catalog supplement" packet with blue-colored pages added and replaced pages for the earlier version of the parts catalog. It included 7 new pinball titles not included in the previous version of the parts catalog. Later catalogs had these new pages included and were not colored blue. | ||
| Williams | Blue Parts Catalog (1984-1989) | 16-9064-B | Viewer |
Banzai Run, Big Guns, Black Knight: 2000, Comet, Cyclone, Earthshaker!, F-14 Tomcat, Fire!, Grand Lizard, High Speed, Jokerz!, Millionaire, Pin Bot, Police Force, Road Kings, Sorcerer, Space Shuttle, Space Station, Swords of Fury, Taxi | This is the latest version of the blue parts catalog. It included the game titles in the previous version, information from the supplementary parts catalog, a few new pinball titles, and a total of 5 shuffle alley titles. The blue parts catalog came in a blue-colored binder with the catalog's cover and game titles printed on the front, and basic information printed on the spine. The pages of this catalog were printed on pink paper.
| |
| Williams | Red Parts Catalog (1989-1990) | 16-9190 | Bad Cats, Diner, Rollergames, Whirlwind | The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This version of the parts catalog included 4 pinball titles and 2 shuffle alley titles. The pages were printed on white-colored paper. | ||
| Williams | Red Parts Catalog | 16-9190-A | (currently unverified) | The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This was a supplementary parts catalog that updated pages and added titles to the previous version of the red parts catalog. The pages were printed on blue-colored paper. | ||
| Williams | Red Parts Catalog (Supplementary Catalog) (1989-1992) | 16-9190-B | Viewer |
Bad Cats, Diner, Dracula, Fish Tales, Funhouse, The Getaway, Hurricane, The Machine: Bride of Pin Bot, Riverboat Gambler, Rollergames, Slugfest, Terminator 2, Whirlwind, White Water | The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This version of the parts catalog included 13 pinball titles, and 5 shuffle alley titles, 7 video came titles, and 3 novelty game titles. The pages were printed on gray-colored paper. | |
| Bally/Midway | Yellow Parts Catalog (1988-1990) | 16-9147 | Atlantis, Elvira, Game Show, Mousin' Around, Transporter, Truck Stop | The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. The pages were printed on white-colored paper. | ||
| Bally/Midway | Yellow Parts Catalog (Supplementary Catalog) (1988-1991) | 16-9147-A | Atlantis, Bugs Bunny, Dr. Dude, Elvira, Game Show, Harley Davidson, Mousin' Around, Pool Sharks, Radical!, Transporter, Truck Stop | The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. This was a supplementary update to the previous version of the catalog, which included 11 pinball titles and 4 video game titles. The pages were printed on yellow-colored paper. | ||
| Bally/Midway | Yellow Parts Catalog (1988-1992) | 16-9147-B | Viewer |
Addams Family, Atlantis, Black Rose, Bugs Bunny, Dr. Dude, Dr. Who, Elvira, Game Show, Gilligan's Island, Harley Davidson, Mousin' Around, Party Zone, Pool Sharks, Radical!, Transporter, Truck Stop | The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. The pages were printed on gold-colored paper. | |
| Bally/Midway | Gray Parts Catalog (1992-1994) | 16-9562 | Creature From the Black Lagoon, Judge Dredd, Popeye Saves the Earth, Twilight Zone | The gray parts catalog came in a white-colored binder with gray colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. The pages were printed on white-colored paper. | ||
| Bally/Midway | Gray Parts Catalog (Supplementary Catalog) (1992-1995) | 16-9562-A | Viewer |
Addams Family Gold, Corvette, Creature From the Black Lagoon, Indianapolis 500, Judge Dredd, Popeye Saves the Earth, The Shadow, Theatre Of Magic, Twilight Zone, Who Dunnit, World Cup Soccer | The gray parts catalog came in a white-colored binder with gray colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. This was a supplementary update to the previous version of the catalog. The pages were printed on light blue colored paper. | |
| Williams | Green Parts Catalog (1993-1995) | 16-9932 | Viewer |
Demolition Man, Dirty Harry, Demolition Man, Indiana Jones, Road Show, Star Trek - Next Generation | The green parts catalog came in a white-colored binder with green colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. There was no supplementary update to this catalog. | |
| Williams | Genuine Replacement Parts Catalog (1997-1998) | 10/97 | Viewer | This catalog mainly provides listings, parts numbers, and drawings of commonly replaceable generic pinball parts for Bally/Williams games, such as flipper assembly parts, target parts, posts, springs, connectors, coils, plungers, etc. It does not contain any game-specific information. |
4.4 Service Bulletins
Supplementary service bulletin books were released, which included service bulletins that detailed any problems or issues with games that were discovered after they were released.
| Manufacturer | Catalog | Cover | Source | Games | Notes |
|---|---|---|---|---|---|
| Williams | Service Bulletin Book, 1991 | Funhouse, Gilligan's Island, Harley Davidson, Slugfest, Terminator 2 | This book includes some System 11 games.
| ||
| Williams | Service Bulletin Book, 1992 | Addams Family, Funhouse, Hurricane, Party Zone, Terminator 2 | |||
| Williams | Service Bulletin Book, Fall 1992 | Addams Family, The Getaway, Strike Master (shuffle alley) | |||
| Williams | Service Bulletin Book, 1993 | Black Rose, Creature From the Black Lagoon, Doctor Who, Dracula, Fish Tales, NBA Jam, White Water | |||
| Williams | Service Bulletin Book, 1994 | Dracula, Indiana Jones, Judge Dredd, Star Trek the Next Generaton, Twilight Zone |
| ||
| Williams | Service Bulletin Book, Fall 1994 | Popeye, Indiana Jones, Star Trek, Addams Family, Demolition Man, Flintstones | |||
| Williams | Service Bulletin Book, 1995 | World Cup Soccer, Corvette | |||
| Williams | Service Bulletin Book, 1996 | Congo, No Fear, Indianapolis 500, Jackbot, Johnny Mnemonic, Road Show, The Shadow, Theatre of Magic | |||
| Williams | Service Bulletin Book, 1997 | Johnny Mnemonic, Junkyard, Safecracker, Scared Stiff, Tales of the Arabian Nights | The last service bulletin included in this book was service bulletin 96. | ||
| Williams | Service Bulletin Book, 1998 | PDF (incomplete) | Scared Stiff, NBA Fastbreak, Cirqus Voltaire, Medieval Madness | According to the table of contents, this includes (pinball) service bulletins 98, 99, 101, 102, 104, and two others. The original color of the cover is currently unknown. The PDF scan only includes some of the Medieval madness service bulletin and the fastbreak link kit installation instructions. | |
| Williams | Service Bulletin Book, 1999 | The original color of the cover is currently unknown. Dated September 10, 1999. Presumably includes at least (pinball) service bulletin 107. |
Individual Game-Specific Service Bulletins:
| Service Bulletin | Date | Game(s) | Subject | Notes |
|---|---|---|---|---|
| 93 | 1996-12-20 | Scared Stiff | Solving mechanism problems | |
| 98 | 1997-05-01 | Scared Stiff | Repair Kit for Left Ramp Assembly | |
| 99 | 1997-05-14 | NBA Fastbreak | For a ball trap on the right ramp | Ball trap fix |
| 101 | 1997-12-09 | Cirqus Voltaire | Disappearing Jet Bumper assembly not releasing | Applies to the first 200 sample games |
| 102 | 1997-12-09 | Cirqus Voltaire | Upgrade Kit | Installation instructions for Upgrade Kit #A-22270 |
| 104 | 1998-04-02 | Cirqus Voltaire | Cirqus Voltaire Adjustment Sheet | Adjustment Sheet Update |
| ? | 1998 | Medieval Madness | Wireform Adjustment | Catapult wireform adjustment (description of problem is currently missing, but assumed to help address ball jam issues in catapult wireform) |
| ? | 1997-05-12 | NBA Fastbreak | Link Kit | Installation instructions for the link kit |
| 107 | 1998-12-28 | Champion Pub | Champion Pub arms breaking prematurely |
4.5 Documentation Errors
- Schematic errors in Addams Family & Addams Family Gold Manuals for the Extra Flipper Power Supply Board (A-15416).
- WPC SChematic Manual 16-9473 to 16-9473-2: Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.
5 Technical Info
At the heart of the WPC MPU is the Motorola 68B09EP microprocessor, running at 2Mhz. Note that the "E" suffix indicates externally clocked and is necessary to work in a WPC MPU. The "P" suffix merely indicates a "plastic" chip case. 6809 processors lacking the "E" suffix will not work in a WPC MPU.
The 68B09EP is a 2Mhz, 8-bit/16-bit CPU, with a 64KB address space. Bank switching is required to address more than 64KB. Bank switching is accomplished by the ASIC in WPC systems. The game ROM size varies from 128KB to 8MB, depending on the game. 8KB of battery backed RAM is available to the processor.
For more information, see The FreeWPC Manual (Archive.org link)
5.1 Inside WPC Game Backboxes
- Typical WPC-089, WPC-DCS, and WPC-95 backbox configurations
WPC-089 pre-DCS 
WPC-089 pre-DCS with FlipTronics 1 (Addams Family, note separate 50V power supply board) 
WPC-089 with DCS (Demolition Man) 
WPC-S with DCS (Theatre of Magic) 
WPC-95 (Attack From Mars, Color DMD Installed)
5.2 WPC Parts List Lookup
A really nice utility has been put together by Øyvind Møll, enabling lookup of WPC parts. The utility can be used to see which games used particular parts. The utility can be found here.
5.3 WPC System Generations
5.3.1 WPC CPU
The WPC CPU was the cornerstone of the new WPC pinball system, introduced by Williams in 1990.
The board has the following features:
- Motorola 68B09E processor
- Switch matrix inputs
- 8k of CMOS battery-backed memory
- A single EPROM, sized from 128K (1 megabit, 27C128) to 1M (8 megabits, 27C080 / 27C801)
- Watchdog circuit and master reset
- Three digital I/O ports - general-purpose; display; auxiliary (labeled "display")
- WPC ASIC - an 84-pin PLCC that has decoding, watchdog, and real-time clock circuitry.
What Goes Wrong
Loose Chips - resets and strange behavior
The natural heating and cooling cycle, and vibration, in a pinball machines causes the socketed chips to slowly walk out of their sockets. This loosening can cause mysterious behavior and resets. Firmly pressing each socketed device - including the ASIC - and listening for a small click can solve many odd problems.
Battery Corrosion - rows of switches failing
When batteries reach old age, they always leak electrolyte. In WPC boards, this electrolyte drips onto the switch matrix circuits. There, it causes extensive corrosion. The corrosion will eat up traces under the green solder mask, creating a lumpy appearance. This corrosion is extremely destructive. It must be caught early, and gently washed with vinegar. Damaged components must be replaced, and damaged traces cleaned with a fiberglass brush and carefully tinned with a soldering iron. Battery corrosion can render a board unrepairable, or undesirable.
The Switch Matrix - assorted switch problems
The WPC system, like many pinball machines, uses a switch matrix to read the switches. The matrix is 8 rows by 8 columns, and can read 64 switches with just 16 wires. Under the playfield, the wires snake between the lights, creating strings of rows and strings of columns. The lights are isolated with diodes.
The root cause of switch matrix problems on the WPC CPU is often a voltage short to the switch matrix. This can happen with residual charge from the solenoid or flasher supply, so the machine does not have to be on for damage to occur. One easy way to do this is to touch a coil lug while adjusting slingshot switches. The row detectors - the LM339s - are quite safe from everything but the 70V solenoid voltage, and will often survive that. The column drivers, however, are directly exposed to the wiring. So many shorts - from the GI; lamp matrix; flashers; or solenoid wiring can destroy the driver. A solenoid wiring short will often destroy the 74LS374 at location U14 ahead of the driver as well.
The symptom of a bad driver is a column short that does not go away when the playfield is disconnected. A bad driver may also be confused by neighboring columns, so switches may register twice.
The WPC CPU is stuffed with a "bypass capactor" to the right of the ULN2803. Bypass capacitors filter high frequency noise from the 5VDC power at each integrated circuit (generally). This one...in some revisions of the PCB, isn't connected to anything on one side. It can safely be removed, or more likely, simply not be replaced when abating alkaline corrosion.
5.3.1.1 Early WPC-089 MPU Board as found in Bride of Pin*Bot
The MPU board pictured here is from a Bride of Pin*Bot. Note that J210 and C31 have been replaced.
Some differences between this early board revision and later production revisions:
- Upper right corner parts are quite different
- Mounting holes vs key-holes
- Some sort of "hack" just to the left of the 68B09EP and game ROM.
- Different brand of bypass capacitors (B).
5.3.1.2 WPC-089 Signal Map (pinouts)
The two diagrams (left and right) show the signal pinout for the entire WPC-089 MPU, both front and back side view. Images provided by Sascha Voskuil.
5.3.1.3 WPC-089 Bare PCB Images
The following images are provided for reference.
- WPC-089 OEM MPU PCB Traces
U1 
U2 
U3 
U4 
U5 
U6 
U7 
U8 
U9 
U11 
U12 
U13 
U14 
U15 
U16 
U17 
U18 
U19 
U20 
U21
5.3.2 WPC-S CPU
The WPC-S CPU is the second generation of WPC CPU board. The designer switched to a remote battery holder, located on a daughter board that clips to posts on the lower half of the board. This approach mostly eliminated the PCB damage caused by battery leakage. The next version of the board, the WPC-95 CPU board, switched to a plastic battery holder that doesn't provide quite as much alkaline corrosion protection to the board. The board also has different switch matrix connectors than WPC and WPC-95.
The digital I/O connectors remain unchanged from the WPC CPU.
The most significant difference was the introduction of the security PIC. This devices contains a serial number and a handshake mechanism. The serial number is displayed at startup, and allowed the manufacturer to identify the dealer who sold a machine into a particular region. This approach was necessary when substantial price differences were common across Europe, to prevent grey imports.
To prevent simple removal of the PIC, the device also controlled the switch matrix, and would not operate without a correct machine code from the WPC CPU. Therefore, there is one PIC for each machine. An incorrect or defective chip will result in a "G13 error" or "U22 error" at startup.
When buying a used WPC-S MPU, the battery holder is often missing. If connecting a battery pack, a Molex housing and 2 crimp contacts is needed. The part number for the 5 pin housing is 50-57-9405 (Digikey WM2903-ND). The crimp contacts are part number 16-02-1125 (WM2554-ND).
5.3.3 WPC-95 CPU
The WPC-95 CPU is the third generation of the WPC CPU design. It includes the security PIC added in the WPC-S system, and returns to an on-board battery holder. The new battery holder has a large plastic shell, designed to shield the PCB from any battery leakage. The pinout of the switch matrix connectors changed again from WPC-S.
Note that these pictures show MPUs with the battery holders removed and with the dual .100 headers replaced with "box" headers.
5.3.3.1 WPC-95 CPU Factory Modification
CPUs manufactured for Jack*Bot and Congo sample games before 12-15-95 have a factory modification that includes one cut, an additional diode, and an additional resistor. Williams Service Bulletin 86 details the reason for the mod, premature loss of backup battery voltage.
5.4 WPC Power/Driver Board Generations
5.4.1 WPC-89 Power/Driver Board
The WPC power-driver board converts AC power from the transformer; drives the solenoids; drives the lamp matrix; drives the GI lamps; and detects flipper switch operation in non-FlipTronics machines.
There are three known variants of the WPC-89 driver board: A-12697-1, A-12697-3, and A-12697-4. The A-12697-1 (aka "-1") board is forward-compatible with all WPC-89 & WPC-S games. Because later board versions A-12697-3 ("-3") and A-12697-4 ("-4") boards had components removed due to the introduction of the fliptronics boards, they are not backwards compatible with non-fliptronics games (unless retrofitted with the missing components for older flipper operation).
The power-driver board includes the following functions:
- AC rectification and smoothing for 70VDC solenoid voltage
- AC rectification and smoothing for 20VDC flasher voltage
- AC rectification and smoothing for 18VDC lamp matrix voltage
- AC rectification and smoothing for unregulated 12V supply
- AC rectification and smoothing for 5VDC flasher voltage
- Regulated 12V supply
- Regulated 5V supply
- 6.3VAC supply for GI circuits
- Power control for high power solenoids (drives 1 - 8, Q64 through Q82), with clamping diode connected to 50VDC
- Power control for low power solenoids (drives 9 - 16, Q44 through Q58, with clamping diode connected to 50VDC
- Power control for flashers (drives 17 - 20, Q36 through Q42), without a clamping diode at all
- Power control for "special" solenoids (drives 21 - 28, Q20 through Q34), with clamping diode that must be connected to the power source driving the device. In practice, this is always the 50VDC power source.
- Power control for lamp matrix
- Power control for pre-FlipTronics flippers (not on all boards)
- Sense optos for pre-FlipTronics flippers (not on all boards)
- Power control for 5 6.3VAC GI channels using four-sector triacs
- Zero crossing sense for AC line in
- Logic interface to WPC CPU
5.4.1.1 Retrofit a later driver board to become a -1 version board
The newer generation -3 and -4 boards can be converted to -1 board configuration by populating the following components:
- D39 - 1N4004
- U7/U8 - 4N25 (or 4N35)
- R210/R211 - 3.3K/5W Resistor
- RLY1 - 6VDC 4PDT Relay
- J110 - 9-pin .156 header
- Q99 - 2N5401 transistor
- R208 - 270 ohm 1/4W resistor
- R209 - 4.7K ohm 1/4W resistor
In the image at right, some components remain unpopulated. Those components are part of the line level voltage circuitry that drives LED2 and LED3. The line level voltage circuitry does not work very well and can not be relied upon. Hence, there is no reason to populate those components.
The diagram at left depicts the differences between the -1 and -3 WPC Power/Driver board configurations.
5.4.1.2 WPC Power/Driver Board Layout Errors
5.4.1.2.1 C9 Connection Error
At the time that this PCB was laid out and manufactured, a small tantalum capacitor, located at C9, was connected to the wrong side of the LM323K 5VDC regulator. While it should have been connected to Vin, it was in fact connected to Vout. The picture at left shows a method to correct the board so that it matches the schematics, also shown at left. In this picture, an additional "tab" was added to the top bolt of the regulator and soldered to ground, creating a redundant path to ground for the regulator.
Note that while the schematics show this capacitor as .33µF, it is listed as 2.2µF in each game's parts listing, matching the capacitor that is actually installed.
This change isn't generally considered necessary and not thought to be a significant contributor to game resets. The original purpose of the cap was to filter high frequency noise. According to the LM323K datasheet, a 1 to 2µF tantalum capacitor should be added to the input of the LM323K if the regulator is more than 4" away from the main filter capacitor. The regulator is just inside of 4" from the 15,000µF filter capacitor at C5. As it sits on Vout, it causes no harm, but does no good either.
5.4.1.2.2 J122/J124, pin 1 Connected to Board Ground
Some revisions of the WPC power/driver board, were manufactured with J122 and J124, pin 1, connected to board ground. This would cause whatever is connected to those connector positions, to be turned on constantly. For the game Twilight Zone, this would result in the left mini-playfield magnet being powered constantly. The picture at left shows a factory modification to the power/driver board to rectify the problem.
5.4.2 WPC-95 Power/Driver Board
The WPC-95 Power/Driver board performs all of the same functions as it's WPC predecessor, and also integrates flipper power circuits into the design, eliminating the need for the FlipTronics board present in WPC FlipTronics I & II games as well as WPC-S games. The bridge rectifiers are replaced by ganged 6A2 diodes and the filter capacitors were spec'd down from 15,000µF to 10,000µF. While the WPC P/D board supported brightness control of 5 general illumination circuits, the WPC-95 P/D board can control brightness of only 3 general illumination circuits. The two remaining GI circuits are used for backbox illumination.
5.5 WPC Alphanumeric Display Driver Board
The Alphanumeric display driver board was used in Funhouse, Harley Davidson, and The Machine: Bride of Pin*bot. The board still contains the high voltage handling ICs, UDN6118 and UDN7180. It also has its own high voltage generation circuit that is a carryover from earlier Williams high voltage display circuits.
5.6 WPC Dot Matrix Controller board
The WPC DMD display and DMD controllers are common features in Williams 1990's era pinball machines. The display is a high-voltage plasma system that has scanning electronics built in. The WPC dot matrix controller board, or WPC-95 AV (Audio/Video) board in later machines, provides the power for operation, and maintains the display dot images in its memory. The CPU loads these pages ahead of time, then instructs the display controller to "flip" the images onto the screen.
Note that sometimes U12 is stuffed on this board and sometimes it is not. There is no functional difference whether U12 is stuffed or not.
Clive at the Coin-Op Cauldron has written an excellent article detailing some of the nitty gritty of the DMD controller. The article can be found here.
5.7 WPC Sound Boards
5.7.1 WPC pre-DCS Sound Board
The pre-DCS sound board uses a single LM1875 amp and can accommodate up to 3 sound ROMs. With a single "sound lane" and amp, stereo sound is not possible. The three speakers are connected in series, each of them attempting to accentuate different bands of the audio spectrum. A broken wire to any of the three speakers will result in no sound at all.
5.7.2 WPC DCS Sound Board
With Indiana Jones: The Pinball Adventure, Williams introduced the DCS sound system. Its DSP architecture was a significant improvement on earlier systems, and it allowed Williams to use recorded music from EPROM rather than synthesizer music. The board also introduced dual amplifiers and an electronic crossover. DCS allowed Williams to use compressed sound samples, significantly improving the sound quality of the games.
The board dropped the microprocessor controlled synthesizer chip and sound bite system of earlier WPC machines, and replaced them with the still in production Analog Devices ADSP-2105 DSP. For its time, this was an extremely fast device (40MHz), and is capable of providing all of the sound processing needed in a WPC pinball machine. The ADSP-2115 can also be used as a replacement for the 2105. It adds a second serial port which is not used in WMS pinballs. Williams also upgraded the chip amp. The new chip amp operates at a lower voltage, and forced a corresponding change in the transformer voltage (12VAC + 12VAC). Therefore, DCS machines have different transformer winding to previous WPC machines. The system has an electronic crossover, separating high frequencies to the backbox and low frequencies to the cabinet.
The card connects to the WPC CPU through the I/O port. It shares the port with the Fliptronics board and the display board.
What's on the Board?
The DCS sound board has the following subsystems:
- Rectifier and fused power supply for +/-16VDC amplifier power [check - WPC was 35V?]
- Dual-channel power amplifier with electronic crossover
- DSP-based sound synthesizer
- One EPROM for DSP code storage
- Other EPROMS for sound storage
- High-speed program memory for the DSP
- Mailbox interface for WPC-CPU
On power-up, the board runs a diagnostic and sounds a bong. It does this without any help from the WPC CPU. If there is no bong, the board has a problem.
What Goes Wrong
The smoothing capacitors C20 and C21 are often at the end of their useful lives. The chip amp, like the Honey Badger, really doesn't care, and will accomodate capacitor variance. However, replacing them will make even the pre-DCS sound much richer.
The coupling capacitors at C32 and C41 can fail.
5.7.3 WPC-95 AV Board
The WPC-95 AV board integrated the sound and video system into a single board, siginifcantly reducing power and space.
The board has the following major subsystems
ASIC The ASIC is a 120-pin quad flatpack device. It incorporates the following functions:
- Interface registers to CPU
- Memory control and display output logic for the diaplay subsystem
- Memory interface for the AD2105 DSP
The ASIC has a tendency to fail in such a way that the sound disappears. New ASICs are available, but replacing them requires skill with surface mount devices.
Audio DSP The audio susbsystem uses the same part as the DCS sound board the Analog Devices DSP part ADSP-2105 and an AD1851 DAC. For its time, this was an extremely fast device (40MHz), and is capable of providing all of the sound processing needed in a WPC pinball machine. The AD1851N in DIP package was discontinued 2010 but the DSP is still available at Digikey and many other stores (ADSP-2105BPZ-80 ).
Location: lower center of board
Serial Port The serial port is rarely populated. Its uses include: machine debugging; machine linking (NBA Fastbreak); ticket printers
Location: lower left of board
Audio Amplifier The audio amplifier is a dual-channel TDA 2030A operating at X volts. The system has an electronic crossover, separating high frequencies to the backboox and low frequencies to the cabinet.
Location: lower right of board
DMD Power The DMD nominally requires 62, -100 and -112VDC to operate. The board uses a temperature-compensated design to supply these voltages.The -112VDC line is built as a 12V offset from the -100VDC line.
Location: upper right of board.
5.8 WPC FlipTronics I & II Boards
Beginning with The Addams Family, Williams implemented the FlipTronics flipper power and switch sensing system. The Addams Family and The Addams Family Gold were the only two games which used the FlipTronics I board. Subsequent games until the WPC-95 board set debuted used the FlipTronics II board. FlipTronics II boards are backward compatible with the FlipTronics I board. The three FlipTronics II board revisions (A-15472, A-15072-1, and A-15472-1) are interchangeable. The WPC-95 board set integrated the flipper electronics into the driver board.
Prior to the FlipTronics system, flipper circuit design had essentially been the same simple circuit. This circuit consisted of power to two flipper coil windings (the "power stroke" and "hold" windings). When the flipper cabinet switch was closed, the power winding and hold winding were both energized. As the flipper plunger was pulled in, the flipper EOS switch opened, interrupting power to the "power stroke" winding, leaving only the "hold winding" energized to hold the flipper in the up position. Flipper coil systems were designed this way so a flipper could be energized indefinitely (in theory). A failed EOS switch could result in weak flipper performance (poor EOS switch conduction) or result in burned flipper coils (EOS switch that never opens).
The FlipTronics system ended reliance on properly operating EOS switches. While FlipTronics systems still have EOS switches, they generally are not used to control power to the coil windings. The EOS switch provides feedback to the MPU that the flipper has completed a stroke. A failed EOS switch will not cause damage to either the coil or to the switch circuitry. If the MPU doesn't receive feedback that the flipper has completed a full stroke within a specific time (milliseconds), the "power stroke" winding power will still be interrupted.
There is a special case where a properly operating EOS switch comes into play. The EOS switch on FlipTronics games helps to keep the flipper bat in the up position when a fast moving pinball strikes the flipper. When the ball strikes the flipper, moving it toward the "at rest" position, a properly operating EOS switch will open. The FlipTronics board will then provide a path to ground for the "power stroke" winding until the flipper completes the upward stroke, closing the EOS switch again. Games with broken or malfunctioning EOS switch(es) may allow the flipper bat to drop all the way to the "at rest" position when struck by a rapidly moving ball, with possible loss of ball, and a great deal of "what the @#$% just happened".
FlipTronics game flipper operation:
- Flipper power is always present at the flipper coil lugs. For the flipper to actuate, that coil power needs to find a path to ground.
- The FlipTronics board switch sensing circuitry recognizes closure of a flipper cabinet switch.
- The FlipTronics board communicates closure of the flipper cabinet switch to the MPU.
- The MPU commands the FlipTronics board to provide ground for the "power stroke" winding of the flipper coil (via a circuit passing through a 2N5401, TIP-102, and TIP-36C). This process is similar to how high powered coils are controlled by the power driver board.
- A few milli-seconds later (thousandths of a second), the MPU commands the FlipTronics board to interrupt the ground path for the power stroke winding and to provide ground for the hold winding portion of the coil (via a circuit passing through a 2N5401 and a TIP-102).
- The FlipTronics board switch sensing circuitry recognizes close of the flipper EOS switch, and communicates that switch closure to the MPU. Again, this switch closure isn't used to control power to the flipper coil windings. It's merely information.
- When the player releases the cabinet flipper switch, the FlipTronics board again senses that open switch, communicates the change in state to the MPU which then commands the FlipTronics board to interrupt ground to the hold winding also, and the flipper returns to it's at rest position.
WPC-95 games use the exact same methods. However, the WPC-95 board set integrates the capabilities of the FlipTronics board into the power driver board.
The FlipTronics II board also rectifies AC voltage sourced from the game transformer, and relayed to it from the Power/Driver board to create the 70VDC flipper power (the FlipTronics I board relies an an "extra flipper power supply" to rectify the flipper voltage). A FlipTronics board can sense 8 switches, and control up to four flipper power and hold windings. In some games, spare flipper cabinet switches, EOS switches, and coil drive circuits are used for other game features.
Note that sometimes C2 is installed on this board and sometimes it is not. The board pictured does not have C2 installed. Since C2 is a 100µF/100V capacitor, it can't be doing too much AC smoothing of the full wave rectified flipper power. Some RGP discussions indicate that C2 may have been designed in originally to reduce EMI (electro-magnetic interference) from the board. Installing C2 will have a negligible affect on flipper power. Some report that installing C2 fixes a "jittery gate" symptom on BSD's "mist" assembly.
More information about bench testing FlipTronics board is available here.
5.9 Miscellaneous WPC Boards
5.9.1 WPC 7 Opto Board (A-14977, A-15576, A-15595)
The 7 Opto Board is used in the following games:
- Attack from Mars
- Cirqus Voltaire
- Demolition Man
- Flintstones
- Jackbot
- Judge Dredd
- Johnny Mnemonic
- NBA Fastbreak
- Road Show
- The Addams Family
- The Addams Family Gold
- Theatre of Magic
- Tales of the Arabian Nights
- World Cup Soccer
- White Water
The connector on the lower left (as pictured) provides the power for seven IR emitters. The emitters are powered from the 12V supply through a 260 ohm resistor (the large blue resistors adjacent to the connector). Williams runs the opto emitters at about 40mA, which results in the resistors becoming hot. The opto boards are often darkened by the heat, as this one is.
The connector on the upper left carries the signals for the photo-transistors. The photo-transistor collector connects to 12V, and its emitter connects to ground through two 2KOhm resistors connected in series. When the transistor is illuminated by the emitter, it passes more current through the resistors, raising the input voltage on the LM339. The other pin on the LM339 is set to about 2.8V buy a 100K/22K voltage divider. Therefore, when the voltage at the junction of the two 2K resistors and the LM339 input is above 2.8V, the switch will read as closed. This happens at 1.4mA.
The two left side connectors can be used for optical trough switches. The connector on the right hand side provides the the row/column switch matrix interface to the MPU.
5.9.1.1 WPC 7 Opto Board Problems
What Goes Wrong?
The resistor discoloration is cosmetic, and rarely causes problems. The biggest problem for these boards is switch matrix shorts. If any of the power lines hits the switch matrix, it can easily destroy the LM339 and possibly its output diode. This issue will manifest as a ground short on one or more rows. It can be tested by removing the switch matrix connector. If the problem goes away, the associated LM339 and possibly its diode need to be replaced.
If the short was from the 70V supply, multiple LM339s may be damaged.
Replacing LM339s on these boards needs to be done carefully, as it is easy to lift traces and pull the through-hole plating. Always socket replaced ICs.
5.9.2 WPC 10 Opto Board (A-15430, A-18159, A-20246)
The 10 opto board was used in Bram Stoker's Dracula, Dr. Who, Indiana Jones, Pinball Circus, Popeye, Cactus Canyon, Corvette, Monster Bash, Medieval Madness, Revenge From Mars, SafeCracker, SWE1, Shadow, Congo, Indianapolis 500, and World Cup Soccer.
The connector on the upper left carries the power for seven of the IR emitters. The emitters are powered from the +12V supply through a 260 ohm resistor (the large blue resistors adjacent to the connector). Williams runs the opto emitters at about 40mA, which results in the resistors becoming hot. The opto boards are often darkened by the heat, as can be viewed in the adjacent picture.
The connector on the lower left carries the signals for the photo-transistors. The photo-transistor collector connects to +12V, and its emitter connects to ground through two 2KOhm resistors connected in series. When the transistor is illuminated by the emitter, it passes more current through the resistors, raising the input voltage on the LM339. The other pin on the LM339 is set to about 2.8V by a 100K/22K voltage divider. Therefore, when the voltage at the junction of the two 2K resistors and the LM339 input is above 2.8V, the switch will read as closed. This happens at 1.4mA.
These two connectors can be used for optical switch troughs. The three connectors on the right hand side each carry signals for one transmitter/receiver pair. These connections are often used for ramp entrances, and sometimes the pair is mounted on a single bracket.
The connector on the bottom provides the the row/column switch matrix interface to the MPU.
5.9.2.1 WPC 10 Opto Board Problems
What Goes Wrong?
The resistor discoloration is cosmetic, and rarely causes problems. The biggest problem for these boards is switch matrix shorts. If any of the power lines hits the switch matrix, it can easily destroy the LM339 and possibly its output diode. This issue will manifest as a ground short on one or more rows. It can be tested by removing the switch matrix connector. If the problem goes away, the associated LM339 and possibly its diode need to be replaced.
If the short was from the 70V supply, multiple LM339s may be damaged.
Other symptoms of failed LM339's can include:
- Intermittent ground shorts on one or more switch matrix rows. Sometimes this can be mistaken for a connector issue since the ground short warning message and row(s) of closed switches in the edge switch test may appear and disappear at random.
- Sometimes the switch edge test can show one or multiple opto switches flickering open and closed. This can sometimes be mistaken for a connector or individual opto issue, as it can come and go at random.
- In switch edge test, one opto switch can activate an entire row of opto switches, but might not actually show the ground short warning.
Replacing LM339s on these boards needs to be done carefully, as it is easy to lift traces and pull the through-hole plating. Always socket replaced ICs.
Another common issue is the 100uf/35V electrolytic capacitor at C1 will leak corrosive liquid that eats through the traces under it. This interrupts the power supply.
5.9.3 WPC Custom 10-Opto Board (Twilight Zone)(A-16807)
This 10-Opto board appeared only in Twilight Zone. As can be seen, it differs in pinout (at the very least) from the more ubiquitous 10-Opto board above.
What Goes Wrong?
See "WPC 10 Opto Board (A-15430, A-18159, A-20246)", above.
5.9.4 WPC 16 Opto Board (A-16998, A-17223)
This board is used in at least Star Trek: The Next Generation, Junkyard, and Champions Pub. Note the two different "versions". The bracket on one side is believed to be part number 5768-13739-00 while the bracket on the other side is believed to be part number 5768-13739-01. The boards are identical in layout and components. The only difference is bracket mounting, some silk screening, and one version has holes in the PCB which are not used.
5.9.5 8 High Power PCB Assembly (A-16116)
The 8 High Power PCB was used only on Twilight Zone. It has the capacity to drive 8 high power coils if fully populated. Instead, it drives 5 high power coils as populated for Twilight Zone. This simple board is merely an extension of the power/driver board solenoid drive circuitry designed to accommodate the extra coils incorporated into the Twilight Zone design. It replicates the power/driver board circuitry of the TIP-36c transistors.
5.9.6 Auxiliary 8-Driver Board (A-16100)
The auxiliary 8-driver board sits in the top right of the backbox in a handful of WPC machines. The board is designed to run flashers, low-power solenoids, and perhaps motors.
The connector labeling is tricky as the 8-Driver board is controlled by a ribbon cable that is connected to the "Display" connector on the WPC CPU board (J204). The "Display" label is a historical artifact and refers to the alphanumeric display used in Funhouse.
The board has 8 outputs, driven by TIP-102 transistors with a 2N4403 pre-driver, similar to the WPC power/driver board (which uses a 2N5401 as a pre-driver). The board is used in the following games:
- Demolition Man
- Indiana Jones
- Road Show
- Star Trek: The Next Generation
- Twilight Zone
The board circuitry can be jumpered to add one or two more columns to the switch matrix. This makes the board more flexible but also may require different jumpers to use the board in different games (i.e. the boards are not completely interchangeable between games "as is").
Jumpers to be installed for Demolition Man and Roadshow should be...
- PW1, PW3, PW5
Jumpers to be installed for Twilight Zone, Star Trek: The Next Generation, and Indiana Jones should be...
- SW2, SW4, SW6
Indiana Jones, Star Trek: The Next Generation and Twilight Zone use Q12 via the J5-1 connection to add this column. Although Twilight Zone adds the column, the column isn't displayed during switch test (T.1). The column is used to read the 8 optos in the clock mechanism.
The board can be jumpered to respond to memory mapped I/O at addresses 3FEB, 3FED, 3FED, 3FEE, and 3FEF via jumpers W1 through W5. In practice, this feature is never utilized as jumper W4 (3FEB) is always in and jumpers W1, W2, W3, and W5 are always out.
5.9.6.1 Auxiliary 8-Driver Board Problems
What Goes Wrong?
This is a pretty simple board. Generally, the problem is going to be a blown transistor, or rarely, a failed 74ALS576 latch.
A problem which may occur are locked-on coils or flashers. This can be caused by the ribbon cable not being firmly seated. This can happen during the game or in attract mode and is caused by floating data line signals to the 8 Driver Board. A remedy has been found to solve this problem. This involves soldering a 10K resistor from the CLK to 5V and a resistor array 8x10K to pull down all data lines to GND. More information about this modification can be found under the "Diode Tie Back Missing Causes 8-Driver Board Transistor to Fail" section on the Star Trek: The Next Generation page
Another thing to watch for is a "diode tieback" connection to the board for games like Star Trek: The Next Generation. Without this "diode tieback", transistors on the 8-Driver board WILL be damaged. The diode tie-back wire is purple/green and connects from the coil power side of one of the drop target assembly coil lugs to J4 pin 1 on the 8-Driver board. If the solder connection at the coil lug is solid, suspect the wire connection at the IDC connector. Repinning this connection with good a quality crimp-on TriFurcon pin is advised.
5.9.7 Sound Overlay Board (A-13502)
This board acted as a power supply for a small subset of Funhouse and Dr. Dude games during the transition from System 11 to WPC in cases where the WPC boardset still included the System 11 D-11581 sound board.
5.9.8 Attack from Mars "Strobe" Board (A-20669)
The strobe board at left is unique to Attack from Mars. Williams used underrated 100µF/100V non-polarized caps on the board that often fail with the telltale "bulge" at one end. The "transformer" on the board (blue rectangular box, lower/right in the picture) has very fine legs which can break due to vibration at the back of the playfield.
Excellent repair information for this board can be found here and a possible replacement for the overloaded non-polarized capacitors here.
Note: An annotated .pdf of the schematics can be found here.
5.9.9 Trough Opto Boards
When WIlliams moved to the gravity trough, they also switched to optical switches to detect the ball. The trough is covered by a Williams patent.
There are two generations.
The first generation (Judge Dredd - Indiana Jones ???) used a receiver board with all of the switch logic on the board. The vibration in the trough makes extra components subject to failure. The second generation (xxx -) uses a regular opto board, and the trough receiver just has phototransistors.
As with all Williams opto circuits, the transmitters are driven to the very limit, and the series resistors overheat. This overheating destroys the solder joints.
Also, the continued vibration makes the resistor legs crack, and weakens the pins in the IDC connectors.
Later versions used rubber grommets to isolate the boards from the trough.
5.9.9.1 Trough Problems
What Goes Wrong?
5.9.9.1.1 Broken Parts Leads
The resistors on the emitter board are subject to cracked legs. Wiggle them to see if they are good. replace the resistor if there are any signs of trouble. On earlier receiver boards, inspect all components.
5.9.9.1.2 Trough Divots
Balls make great hammers and, over time, they will beat divots into the trough floor. Then, they will then rest in the divots and cause all kinds of ball count problems. The problem is exacerbated with slightly magnetized balls.
The fix is to file them out, and then sand the metal smooth. A dremel tool with grinding stone works great for this.
Installing a shim that slides over the divots is also a fix for this issue. There use to be both metal versions (now PETG) and PETG plastic versions on the market. Only the PETG plastic versions are available now, as far as we know. The shim eliminates the ability of balls to rest in the divots as well as breaking any magnetic connection, especially with the PETG plastic version.
5.9.10 WH2O Chaser Lamp Board (A-15761)
This board is used for the chaser lamps on Whitewater. It is a simple lamp sequencing board that causes the lamps to "chase".
The board rectifies 16VAC via BR1 and BR2 to create approximately 12VDC to power the chase lamps. The board also receives 12VDC from the power/driver board and regulates it down to 5VDC via an LM7805. This 5VDC is used for the logic level ICs on the board.
5.9.11 CFTBL Chase Light II Board (A-15541)
This board is used for the chaser lamps located around the ramps and whirlpool bowl in Creature From the Black Lagoon.
Eight BT138 triacs, which are pre-driven by 2N4403 transistors, control eight discrete lamp strings. In addition to the lamps chasing, the lamp strings can be dimmed for effect.
5.9.12 High Current Driver Board (C-13963)
This board drives the jaw motor for the playfield heckler Rudy in the game Funhouse.
The circuitry is identical to the "Corvette/Road Show Dual H-Drive Motor Control Board" in the next section except that this board controls a single motor only.
5.9.13 Corvette/Road Show Dual H-Drive Motor Control Board (A-19159/A-19242-1)
The "Dual H-Driver Motor Control Board" is used on Corvette and on Road Show. For Corvette, it drives the two small motors that animate the two car race track on the right side of the playfield. For Road Show, it controls both Red and Ted's mouth motors.
While the board has two different part number designations, they are, in fact, identical.
Note: Parts enclosed by "Block A" and "Block B" in the schematics are not stuffed. Parts near "Block C" and "Block D" in the schematics are stuffed with 5.6ohm resistors when used in RoadShow. Those resistors are not stuffed when used in Corvette. Instead, JP1 and JP2 are stuffed.
Operation
The board is powered by either 12VDC (J118/2, Roadshow) or 20VDC (J107/6, Corvette) from the power/driver board.
Each "channel" receives a direction and an enable signal. The signal is either grounded or floating.
Four transistors on the power/driver board provide these signals (three transistors for Corvette as both motors always run in the same direction in game operation, either forward or reverse).
Grounding the "enable" pin for a channel enables power to the associated motor.
Grounding the "direction" pin (or leaving it floating) for a channel causes the motor to turn either clockwise or counterclockwise.
Each channel can be controlled independently. Hence the name, Dual H-Drive.
5.9.13.1 Dual H-Drive Motor Control Board Problems
What Goes Wrong?
Most failures are caused by the two 100uf/35V electrolytic capacitors on the board. They sometimes leak and destroy the power traces beneath them. After that, the TIP102/TIP-107 transistors can fail. These are easily tested using the "diode test". The LM339 is relatively beefy and rarely fails but of course, this is possible.
5.9.14 Bi-Directional Motor Board (A-15680)
This board is used in Cirqus Voltaire, Dr Who, Party Zone and White Water.
One problematic aspect of the board's design is that the 100µF electrolytic cap is mounted over the trace that carries 12VDC power to the drive transistors. If the electrolytic cap fails and leaks it's corrosive contents, it will eat through the trace and the board won't work correctly. If this happens in WH2O, Big Foot will not turn his head during game test at boot up. The board pictured at left exhibited this problem and was repaired.
Note that this cap, C2, was sometimes not stuffed at the factory. It's purpose is to filter noise from the 12VDC power, but the power is clean enough that this cap isn't really necessary. Note also that the schematics for the board are in error, designating this 100µF/25V cap as C1 instead of C2 as is silkscreened onto the board.
Another seemingly prevalent issue with this board is failure of the diodes. If either D8 or D9 fail, the associated motor will turn ONLY counter-clockwise.
The board is controlled by two transistors on the driver board. One transistor "enables" movement of the associated motor. The other determines whether the motor moves clockwise or counter-clockwise.
5.9.15 Double Flipper Opto Switch Board (A-15894) (Type I)
This board is used in early WPC games which used the Fliptronics II board starting with Doctor Who (please confirm first game).
Please note when testing these boards, the right flipper board has to be plugged in for the left board to function. This is due to the +12v and ground connections being daisy-chained through the right board PCB to the left board. The manuals will typically claim the opposite. And in some cases, the +12v is daisy-chained via the right opto board, while the ground is daisy-chained via the left opto board.
It is always best to check the wiring in the game. If two gray or orange wires are connected on one side of the cabinet, the +12v and / or ground are daisy-chained to the the opposite side.
5.9.16 Flipper Opto Board Assembly (A-17316) (Type II)
This board is used in later WPC games which used the Fliptronics II board starting with Indiana Jones (verify) and was used until Pinball 2000.
5.9.17 HSII & CFTBL Triac board (A-13088-2)
This board is used in High Speed 2: The Getaway (for the beacon motor), CFTBL (for the hologram motor), and Hot Shot (basketball redemption game). This triac board was also used in the System 11B game, Whirlwind, under board number C-13088. It was used to control the topper fan.
Since the board is single sided, fractured solder joints are frequently a problem with this board, especially at C1 for some reason. The other failure point on this board is the MOC 3031 otpo-isolator.
5.9.18 24 Inch Opto Board (A-15646)
Note: This board is sometimes referred to as the "24 Switch Opto PC Board".
This board is used on Bram Stoker's Dracula to sense the "Mist Ball" and on Shadow to sense when the ball is at the bottom of the mini playfield. The board is also used in Star Wars: Episode 1, NBA Fastbreak, Judge Dredd, and Hot Shot (basketball redemption game). The usual problem with this board is that the large inductor (marked "106C" in the picture) vibrates off the board. The circuitry on this board is similar to a television remote control circuit. It senses a particular signal frequency.
5.9.19 Eddy Sensor PCB Assembly (A-18543)
This small board is used on Theatre of Magic, Scared Stiff, Road Show and Star Trek: the Next Generation.
This board is connected directly to the WPC switch matrix. Two switch matrix wires, 12VDC and ground are provided at the 4-pin connector. The other two wire connector, as pictured, connects to an inductor mounted into a routed hole in the playfield bottom. Small changes are sensed in the inductor by the board circuitry and indicated on the switch matrix.
5.9.19.1 Eddy Sensor PCB Assembly (A-18543) Problems
What Goes Wrong?
This board can be somewhat problematic.
If the trim POT on the board hasn't been adjusted in quite some time, the POT can form a "dead spot" in the same way that volume POTs do. Twizzling the POT back and forth a few times generally clears this issue.
The POT should be adjusted so that the board is just on the edge of the indicator LED turning off. Test the adjustment by placing a pinball over the sensor on the other side of the playfied.
Note that the sensor will pick up on any metal that is close by. In the picture at left, the playfield brackets were so close that they were causing the sensor to indicate a ball was present. A combination of moving the sensor as far from the metal bracket as possible, and fine adjustment of the trim POT solved the issue.
5.9.20 TAF & TAFG High Power Board (A-15139)
This board (aka magnet board) drives the three under playfield magnets used on The Addams Family and The Addams Family Gold. It is located under the bottom left of the playfield.
5.9.21 TAF & TAFG Extra Flipper Power Supply (A-15416)
This board powers the upper flippers and the playfield magnets for The Addams Family and The Addams Family Gold. It is located just to the right and just above the driver board in the backbox.
The schematics for this board are incorrect in the Addams Family manual. Specifically J903 is shown incorrectly. J903 Pins 1 and 2 supply 50v for the magnet board under the playfield. Pins 3 and 4 are ground for the magnet board under the playfield. The bridge rectifier diagram is also incorrectly rotated by 90 degrees.
5.9.22 The Shadow Five Switch and Diode P.C.B. (A-13940)
This board was used only on "The Shadow" to provide lamp matrix diode isolation for the 4 "Ring Grain of Wheat" lamps. Yes, that's really it's name.
5.9.23 Coin Door Interface Board
The coin door interface board provides signal connection between the coin door switches and the WPC switch matrix and dedicated switches like the "diagnostic" and volume control buttons. The coin door interface board also creates the "always closed" switch 24 by bridging column 2 and row 4 with a diode. WPC games use this "always closed" switch to identify switch matrix power issues.
If the coin door interface board gets dusty from flipper parts wearing, clean it. That dust is conductive and may cause odd coinage issues. There really isn't much that can go wrong with this board.
5.9.24 WPC Alphanumeric Plasma Display Board
Funhouse and The Machine: Bride of Pin*Bot used dual 16-Alphanumeric displays, and a special (specific) high voltage power supply/logic board. The high voltage circuit is similar, if not identical, to late System 11 high voltage power circuits.
Harley Davidson also used dual 16-alphanumeric displays, however, they were placed side by side on separate boards, instead of being "stacked" on one board.
5.9.25 Scared Stiff Crate Board
This simple board mounts to the top of the Scared Stiff crate. It creates the "eyes" that look out the top of the crate. It contains 8 LEDs, 4 current limiting resistors, and 4 diodes, which isolate the LED "lamps" in the lamp matrix. Very little can go wrong with this board other than fractured solder joints, since it lives in a high vibration area of the game.
5.9.26 DC Motor Control Board (A-16120)
This board is used in Cactus Canyon, Demo Man, Monster Bash, No Good Gophers, The Shadow, Twilight Zone, Theater of Magic, World Cup Soccer.
5.9.27 Bridge Driver PCB Assembly (A-15946)
This board is used in Indiana Jones and Hot Shots Basketball. The board is close in design to the A-16120 DC Motor Control Board (above). For Indiana Jones, it controls the Path of Adventure motor, which must turn both clockwise and counter-clockwise.
This simple assembly receives 12VDC power and ground, along with two solenoid connections to the driver board. Grounding one pin of the connection causes +12VDC to be output at the motor power pins. Grounding the other pin will cause -12VDC to be output at the motor power pins.
Indiana Jones uses solenoid 22 to move the POA left and solenoid 23 to move the POA right.
5.9.28 Indiana Jones Path of Adventure (POA) Opto Board
This simple board is used in Indiana Jones to provide "travel limit" feedback to the MPU for the POA. Typical problems include fractured solder joints, since the board experiences a lot of vibration from the POA motor, as well as simple opto failures.
5.9.29 Corvette Z5 Master Board (A-18532), Slave Board (A-19625), and Hall Effect Amplification Board (A-19076)
This pair of boards work together to "rev" the ZR1 LT5 engine toy on the upper left side of the playfield. The master board senses the position of the motor unit using a Hall Effect sensor located below the engine toy assembly. The slave board uses 20V power and four TIP-102s to control four coils below the playfield on the ZR1 LT5 assembly.
Debugging information for the ZR1 LT5 assembly can be found here.
5.9.30 WPC A-13901 / A-17402-3 (and variants) Opto Ramp Switch Board (3 Opto Controller)
There are several variations of the A-13901 / A-17402 3 opto controller board used on several games. Games such as Indiana Jones, CFTBL, Fish Tales, High Speed 2, Hurricane, Slugfest, Funhouse, and Hot Shot all used some version of this board. The part numbers used are:
- A-13901-1-AI
- A-13901-1
- A-13901-2
- A-13901-3
- A-13901-AI
- A-13901
- A-17402-3
5.9.31 WPC A-19043-1 Stepper Motor Driver Board
The Stepper Motor Driver Board is used only in WhoDunnit (Slot Machine Reels). Three of these boards are used to drive the three slot machine reel stepper motors.
5.9.32 A-21967-2 Serial 24 Drive PCB Assembly; aka The Champion Pub LED Driver Board
This board is specific to the single game, The Champion Pub. While resembling an opto board, it drives LEDs.
5.9.33 Coin Doubler Board
This aftermarket add-on board connects atop the direct switches connector on the WPC MPU. It intercepts the coin switches and, for each switch closure it sees, sends the computer two closures. This "hack" effectively halves game pricing. This was done because Williams removed the one-coin-per-play pricing for some games to try and force a price increase.
These are still for sale from Game Boards USA.
5.10 Flipper Coils
WPC games use different flipper coils dependent on flipper placement and application. Below is a chart of the flipper coils used, their wrapper color, and strength.
| WPC Flipper Coils | |||
|---|---|---|---|
| Part # | Color | Strength | Notes |
| FL-11753 | Yellow | Weakest | |
| FL-11722 | Green | Weaker | |
| FL-20867 | White | See notes | Used only in Safecracker |
| FL-11630 | Red | Standard | |
| FL-15411 | Orange | Stronger | |
| FL-11629 | Blue | Strongest | |
Notes:
The FL-20867 flipper coil (white wrapper) was used only on Safecracker. The FL-20867 flipper coil is thought to be between an FL-11722 and an FL-11630 in strength.
Williams also produced an FL-17636 flipper coil (blue wrapper) for use in Star Trek: The Next Generation. This coil is somewhat stronger than the FL-11629, and was used on the prototype games - and some number of production games - to facilitate shots to the Delta ramp. At some point during the ST:TNG production run Williams switched back to FL-11629 coils, perhaps because the Delta ramp shot can be made with an FL-11629 coil with new condition flipper mechs, or due to operator reports of breakage. Still, a large number of games seem to show up with FL-17636 coils, leading one to suspect operators may have swapped out the FL-11629 coils to the stronger FL-17636 coils as the flipper mechs wore. (There is probably an increased chance of breaking playfield plastics and other parts with the FL-17636 coils in place.)
5.11 WPC Transformers
| Part Number | Description | Distinguishing Features | Games |
|---|---|---|---|
| 5610-12718-00 | WPC, 115/230v | (18VAC sound) alphanumeric | BoP, FH, HD |
| 5610-12835-00 | WPC3, 115/230v | (18VAC sound) | BoP, BR, BSD, CFTBL, DW, FH, FT, GI, HD, HS2, Hot Shots Basketball, Hurricane, PZ, Slugfest, T2, TAF, TAFG, TZ, WH2O |
| 5610-13491-00 | WPC Power | (12VAC sound) | IJ, JD, Pinball Circus, Popeye, STTNG |
| 5610-13953-00 | WPC94 | (female line input) | Corvette, DH, DM, FS, RS, Shadow, WCS |
| 5610-14515-00 | WPC Wide Mount | AFM, Congo, I500, JB, JM, NF, SC, SS, ToM, TOTAN, WD | |
| 5610-14515-01 | WPC Wide Mount | AFM, CC, CP, CV, Congo, I500, JB, JM, JY, MB, MM, NBA, NF, NGG, SC, SS, ToM, TotAN, WD | |
| 5610-15930-00 | transformer p2000 | RFM | |
| 5610-15930-01 | transformer p2000 | SWE1 |
5.11.1 Primary Voltage Selection Jumpers at the Transformer
On all WPC games, there are either a 9 pin or 12 pin Molex connector used to change the primary voltage setting fed to the transformer. 9 pin connectors were connected to a pigtail off the transformer itself. Later units used a 12 pin connector on the power source metal box located inside the cabinet floor on the right just inside the coin door. Depending on the placement of the jumpers, common configurations are 115v (typical domestic setting), 230v (European setting), and 100v (Japanese setting).
It is common to change the voltage setting (220 to 120 volt conversion) if a game is re-imported back into the US. Although probably more common at the moment is to convert a domestic game to 220 volts (more games are currently being exported from the US than imported).
All voltage selection pins are .093 molex pins. Removal of the pins requires a special molex tool. See "Headers, Housing, and Crimping.
Important Notes:
- When jumpered for 120V operation, the line fuse is an 8ASB, and a 130V Varistor is used.
- When jumpered for 230V operation, the line fuse is a 5ASB, and a 260V Varistor is used.
5.11.2 Early WPC Transformers (9 pin connection)
The 9 pin connectors used are Molex 19-09-2099 (butterfly connection w/jumpers) and Molex 19-09-1099 (connection on transformer pigtail).
Jumper settings for 115V should be as follows:
- Pin 1 - black - 115v "hot" input
- Pin 7 - white - 115v "neutral" input
- Pins 2 and 3 jumped together
- Pins 8 and 9 jumped together
Jumper settings for 230V should be as follows:
- Pin 1 - black - 230v "hot" input
- Pin 7 - white - 230v "neutral" input
- Pins 3 and 9 jumped together
5.11.3 Later WPC Transformers (12 pin connection)
Jumper settings for 120v should be as follows:
- Pins 1 and 11 jumped together
- Pins 2 and 3 jumped together
- Pins 7 and 10 jumped together
- Pins 8 and 9 jumped together
The 12 pin connector used is Molex 19-09-1129.
Jumper settings for 240V should be as follows:
- Pins 1 and 11 jumped together
- Pins 7 and 10 jumped together
- Pins 3 and 9 jumped together
5.12 Unused Connectors
Some WPC games include connectors in the backbox or under the playfield that are not used in the production configuration of the game. Possible reasons for this include:
- Connectors were originally installed to support features that were later removed when the game went to production. It was easier/cheaper to simply leave the connectors in place.
- The connectors may have been test connectors that could be used during assembly to ensure all features were operating correctly.
- As explained by a former cable harness designer, some automated wire cutters were limited to a maximum cut length (perhaps 100 inches). If the harness required a wire longer than the maximum cut length, the factory would include a molex connector in the design to achieve the necessary length piecemeal.
6 Problems and Solutions
6.1 Jumpers, RAM and ROM size
RAM Size
The WPC-089 MPU can be configured for two different RAM sizes. This is done with jumper W3 and resistor R93 as shown below.
- 6264 RAM - W3 out, R93 in (a 1.5K 1/4W resistor)
- 62256 RAM - W3 in, R93 out
Both RAM sizes work fine in all games. Williams probably provided this flexibility to allow use of whichever RAM was cheaper or more available. Note: Most NVRAM replacements are 6264 replacements.
The WPC-95 MPU can be configured for two different RAM sizes. This is done with jumper W3 (only) as shown below. R93 is always installed.
- 6264 RAM - W3 out
- 62256 RAM - W3 in
Again, both RAM sizes work fine in all games and most NVRAM replacements are 6264 replacements.
ROM Size
The MPU can also (and needs to be) jumpered for different ROM sizes. This becomes important when upgrading ROMs or swapping a CPU (and ROM) into a different game. Games like Funhouse shipped with a 1M ROM, jumper W2 in, and jumper W1 out. Updating the Funhouse ROM to a larger size ROM requires W1 in and W2 out.
The official Williams ROM size/jumper settings are shown below.
- 512K/1M - W1 out, W2 in
- 2M/4M - W1 in, W2 out
6.2 Test ROMs
Test ROMs are available from Planetary Pinball, but they should only be used in conjunction with a test fixture and not installed in an actual game, as per the official recommendation.
6.3 Country DIP Switch (or jumper) Settings
The message shown at left occurs sometimes when the game software seems to want the "country code" jumpers to be configured in a certain way. The simple solution (for English speaking users) is to remove the jumpers noted in the message by cutting them off. This sets the board to "AMERICA2". Twilight Zone, and perhaps game ROM version 9.4H, seem to prefer the "AMERICA2" country code. Other country code jumper configurations are shown below.
Two WPC-089 MPUs are shown at left. Early versions of the MPU used "zero ohm resistors" or jumpers to figure the country code. Later versions of the MPU (as well as WPC-S and WPC-95 MPUs, used DIP switches.
Note: If a dip switch is installed, always leave W11 and W12 in the OFF position. If both are set on ON, the undervoltage detection circuit on the WPC Power/Driver will not work and both LED2 and LED3 will always remain on.
The complete WPC-089 country code jumper table is shown at left.
The complete WPC-S/WPC-95 country code jumper table is shown at left. WPC-S/WPC-95 MPUs do not have an "AMERICA2" configuration.
6.4 Power-On LEDs and Sound Tones (Bongs)
When the game is booted, several LEDs in the backbox will light, and the game may provide sound "bongs" to indicate diagnostic status.
A properly booting WPC game will show a "progress bar" on the DMD along with a "ticking" sound which results from a series of reset signals being sent to the sound board. After a successful boot, the sound board will create a single "bong" tone.
6.4.1 LEDs on the MPU
Note: WPC and WPC-S games label the MPU and Power/Driver board LEDs as "Dxx". WPC-95 games label these same LEDs "LEDxxx".
- D19 (LED201) - "Blanking". This LED should light when power is applied, then after about 1 second, go off and stay off. If D19 remains on, this is an indication that the blanking circuit is turned on which prevents the game from powering coils. The blanking circuit was implemented to eliminate the possibility of damaging the game due to locked on coils when the CPU isn't operating properly.
- D20 (LED203) - "Diagnostics". Once the blanking LED turns off, this LED should begin blinking and remain blinking as long as the game is turned on. This LED is a simple "I'm working" indication from the MPU. This LED is toggled from pin 35 of the ASIC (DLED signal). D20 will also indicate basic issues with the MPU by blinking as such...
- One blink - problem with the game ROM.
- Two blinks - problem with the game RAM (or accessing the RAM, i.e. open traces).
- Three blinks - problem with the ASIC (WPC) or a problem with the security chip (WPC-S and WPC-95).
- D21 (LED202) - "5VDC present". This LED provides a simple indication of the presence of 5VDC. This LED isn't CPU controlled. It's illuminated as long as 5VDC is present.
A YouTube video of an MPU blinking D20 twice, indicating a RAM issue, can be found here.
Note: It is possible for the switch column IC, U20, to be blown and the damage continuing upstream to U14. In this case, it is possible that the data signals become corrupt and prevent the MPU from booting. D19 and D21 will light but D20 will never light.
6.4.2 LEDs and test points on WPC-089 Power/Driver Boards
The image at left shows the 5 LEDs that are normally lit, forming a "bow tie" (or X-Wing Fighter, if you prefer). Note that some WPC Power/Driver boards are populated with LED2 and LED3 which were meant to indicat high/low line voltage. In practice, those LEDs don't provide that information very well, and should be ignored.
| LED/Test Point | Explanation |
|---|---|
| Normally lit. Indicates presence of regulated 12VDC (12VR). AC voltage is rectified to about 18VDC by BR1 and smoothed by C6 and C7 (this power is tapped for the lamp matrix). D1 and D2 are used to drop the voltage by 1.0 to 1.4V and then the voltage is further regulated down by the LM7812 at Q2. This 12VDC power is shown as "+12V Digital" on the schematics. This power is fused by F114. If LED6 isn't lit, LED1 won't be lit either. | |
| If installed, provides an indication of high/low line voltage. This LED isn't very useful as it will flicker as power consumption by the game fluctuates. | |
| If installed, provides an indication of high/low line voltage. This LED isn't very useful as it will flicker as power consumption by the game fluctuates. | |
| Normally lit. Indicates presence of regulated 5VDC. AC voltage is rectified by BR2 and smoothed by C5. The voltage is regulated down by the LM323K at Q1. This 5VDC power is shown as "+5V Digital" on the schematics. This power is fused by F113. | |
| Normally lit. Indicates presence of unregulated 20VDC. AC voltage is rectified by BR4 and smoothed by C11. The voltage is used to power the flash lamps. Note that beginning sometime during production of Twilight Zone in 1993, a "coin door interlock" switch was added. This switch interrupts power to both the 20VDC and 50VDC circuits when the coin door is opened, providing a measure of safety against higher voltage shocks. If the coin door is opened with power applied, this LED will fade to off. It will not light with the coin door open. This power is fused by F111. | |
| Normally lit. Indicates presence of unregulated 18VDC. AC voltage is rectified to about 18VDC by BR1 and smoothed by C6 and C7. This 18VDC power is used to power the lamp matrix lamps. This power is fused by F114. | |
| Normally lit. AC voltage is rectified to about 12VDC by BR5 and smoothed by C30 to provide unregulated 12VDC power. This 12VDC power is shown as "+12V Power" on the schematics. It is used to power motors, optos, and other game features that do not require a precise 12VDC. This power is fused by F116. | |
| Zero Cross. By using an oscilloscope, this test point allows testing of the "zero cross" circuitry. "Zero cross" is when the AC sine wave crosses through the zero voltage point relative to ground. Zero cross is important for the proper operation of the general illumination lamp circuit. | |
| Ground. This test point stud may be used to measure all DC voltages against. | |
| 50VDC power. This test point will actually measure 70 - 75VDC, which is normal and expected. This power is used for all coils in the game including the flippers. This power is fused by F112. Individual coil power circuits are fused by F101 thru F105. F112 protects both BR3 and the bridge rectifier circuit on the FlipTronic II board. Should F112 blow, remove J104 (or J105). Replace the fuse. Power on. If the fuse blows, BR3 has probably failed. If it holds, the bridge rectifier on the FlipTronics II board has probably failed. |
6.4.3 LEDs and test points on WPC-95 Power/Driver Boards
| LED/Test Point | Explanation |
|---|---|
| Normally lit. Indicates presence of regulated 12VDC. AC voltage is rectified to about 18VDC by D11-D14 and smoothed by C11 and C12. D1 and D2 are used to drop the voltage by 1.0 to 1.4V and then the voltage is further regulated down by the LM7812 at Q2. This 12VDC power is shown as "+12V Digital" on the schematics. | |
| Normally lit. Indicates presence of regulated 5VDC. AC voltage is rectified by D7-D10 and smoothed by C9. The voltage is regulated down by the LM317K at Q1. This 5VDC power is shown as "+5V Digital" on the schematics. | |
| Normally lit. Indicates presence of unregulated 18VDC. AC voltage is rectified to about 18VDC by D11-D14 and smoothed by C11 and C12. This 18VDC power is used to power the lamp matrix lamps, and is subsequently regulated to 12V for use in the switch matrix. | |
| Normally lit. AC voltage is rectified to about 12VDC by D3-D6 and smoothed by C8 to provide unregulated 12VDC power. This 12VDC power is shown as "+12V unreg" on the schematics. It is used to power motors and other game features that do not require a precise 12VDC. | |
| Normally lit. Indicates presence of unregulated 20VDC. AC voltage is rectified by D15-D18 and smoothed by C10. The voltage is used to power the flash lamps. Note that a "coin door interlock" switch is present on all WPC-95 games. This switch interrupts power to both the 20VDC and 50VDC circuits when the coin door is opened, providing a measure of safety against higher voltage shocks. If the coin door is opened with power applied, this LED will fade to off. It will not light with the coin door open. | |
| Normally lit. Indicates presence of unregulated 50VDC. This test point will actually measure 70 - 75VDC. This power is used for all coils in the game. AC voltage is rectified to about 75VDC by D19-D22 and smoothed somewhat by C22. | |
| Zero Cross. By using an oscilloscope, this test point allows testing of the "zero cross" circuitry. "Zero cross" is when the AC sine wave crosses through the zero voltage point relative to ground. Zero cross is important for the proper operation of the general illumination lamp circuit. | |
| Ground. This test point stud may be used to measure all DC voltages against. |
6.4.4 Power on Sound Tones (Bongs)
After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.
Pre-DCS Sound Board Games.
- 1 - No issues...enjoy a game.
- 2 - U9 RAM failure.
- 3 - U18 ROM failure.
- 4 - U15 ROM failure.
- 5 - U14 ROM failure.
DCS Sound Board Games.
- 1 - No issues...enjoy a game.
- 2 - U2 ROM failure.
- 3 - U3 ROM failure.
- 4 - U4 ROM failure.
- 5 - U5 ROM failure.
- 6 - U6 ROM failure.
- 7 - U7 ROM failure.
- 8 - U8 ROM failure.
- 9 - U9 ROM failure.
- 10 - U10-U12 RAM failure. Note: DCS sound board RAM failures are indicated by a message on the display, "U10-U12 RAM error".
Audio/Video Board Games (WPC-95).
- 1 - No issues...enjoy a game.
- 2 - S2 ROM failure. Note: Two bongs also occur if jumper W3 is IN, and the RAM size is 6264. If an NVRAM was just installed, check this jumper. See the section on jumpers.
- 3 - S3 ROM failure.
- 4 - S4 ROM failure.
- 5 - S5 ROM failure.
- 6 - S6 ROM failure.
- 7 - S7 ROM failure.
- 10 - U9, U10, or U11 RAM failure (see below)
A/V sound board RAM failures are indicated by a message on the display, either "U9-U11 RAM error" or "U10-U12 RAM error". This is apparently game software dependent. A/V RAM are, in fact, U9-U11. Apparently, this message wasn't updated in the software with the introduction of the A/V board.
6.5 Fuses
Fuses are used to protect the various game circuits when a problem arises and the circuit begins to draw more current than originally designed to draw.
The best way to test a fuse is to remove it from it's fuse holder and "buzz" it with a DMM set to continuity. This method will prevent false positives via "sneak circuits". When removing fuses from a RottenDog aftermarket power/driver board should be done with extreme care as the fuse clips are easily bent and damaged.
6.5.1 WPC/WPC-95 Fuse Tables
A typical WPC fuse table is shown at left, WPC-95 fuse table at right.
6.5.2 F111 Blows, Testing BR4 With Board Still Installed
Fuse F111 sits between the transformer secondary and BR4. BR4 recitifies AC power for the flash lamps. If BR4 failes shorted, F111 will blow, protecting the transformer secondary winding.
BR4 can be tested "in situ" using the method shown in the animated gif at left.
Note: This test requires a good fuse to be in place at F111 for the test to work properly.
6.6 Melted Blue/White Transformer Secondary Wires at Connector J101
It is poor practice to repin less than the complete connector. Since J101 often burns and can the source of game resets, operators sometimes clip the lower 5 pins of J101, and then "hack" the connector by adding a 4-pin connector for the two blue/white wires that loop through the original IDC connector. With pin 3 being the "key pin", it then becomes possible to connect the hacked 4-pin connector "one pin off". As depicted in the diagram at left, this causes a direct, and un-fused short. The blue/white wires will heat quickly and melt the insulation, acting like fuses. If power is left on long enough, the next victim will the transformer itself.
To avoid this disaster completely, always repin the full connector and always use a key pin and key plug.
6.7 Testing DC Voltages on the Power/Driver Board
A YouTube video showing how to test each of the voltages on the WPC-089 Power/Driver board can be found here.
6.8 Removing or Installing the ASIC
Should ASIC need to be removed from a WPC MPU, it is strongly advised that tthe proper tool is used, as shown at left. The tool is called a PLCC puller.
A video showing the proper technique for removing the WPC ASIC can be found here.
Using a jewelers screwdriver or other such tool can fracture the ASIC chip carrier socket as shown at right. Since these are 84 pins sockets, replacement is non-trivial. Using the incorrect tool may also irreparably damage the ASIC itself by permanently fracturing leg joints, as shown at left.
The ASIC must be oriented correctly when installed. Pin 1 of the ASIC is marked with a dot impression on the top of the chip. Pin 1 of the PLCC socket is marked with an arrow pointing to pin one. This is true for all versions of WPC MPUs. Orient the ASIC as shown in the picture at left relative to the arrow in the socket, center the chip over the socket, and press firmly on the chip center.
6.9 WPC ASIC Pinout
Clicking on the thumbnail at left will open a .pdf file containing pin connections for the WPC (in work) and WPC-S MPUs.
Clicking on the thumbnail at left will open a .pdf file containing a graphic image of the ASIC pinout, provided courtesy of Sascha Voskuil.
6.10 Minimum Parts Required for WPC MPU to Boot
Pictured at left is a partially populated MPU board. It has been included here for those building their own MPU board to indicate a interim state for testing work in progress. The image represents the exact minimum parts required for a WPC MPU to boot. Note that the switch matrix resistors and capacitors are not necessary.
6.11 Game blows power line circuit breaker immediately
Had a thunderstorm roll through or a power surge from the electric company recently?
The varistor in the power box may have done it's job protecting the rest of the game's circuitry from the possibly tremendous power surge.
Signs of a failed varistor are typically black, charred discoloration throughout the "button" portion (green in the case of the adjacent picture) of the varistor. Likewise, varistors can blow rather violently, and there may be charred or burnt remains in the area surrounding the varistor.
Over time, the rating of a varistor will lower, causing "occasional" blowing of the mains fuse. The varistor will visually appear to be OK. A good hint is how violently the fuse blows. Likely varistor problems will cause the fuse to totally obliterate.
Varistors can be purchased from Great Plains Electronics. Order the 130V variant for 120VAC (typically games in the US), and the 275V variant for 240VAC (typically games in Europe).
6.12 Credit Dot
The credit dot is a decimal point (a single, lit pixel on the display), that appears after the number of credits or after the words free play on the DMD display on WPC games. It is a quick indicator used to tell the operator or owner that there may be an issue with the game. Most commonly, there is a switch or multiple switch problems with the game. However, a credit dot will appear for other reasons, such as when the date and time are not set.
If, after 30 balls or 10 games, a particular switch hasn't registered, the credit dot is posted to alert the user to check the diagnostics. Some high usage switches will trigger the alert earlier. The credit dot may or may not indicate a real problem. For the example shown in the pic, it's simply reporting a switch that is hard to hit in the game. So, the credit dot is actually saying "Play Better". :-)
6.13 Battery Issues
6.13.1 Relocating the battery from the MPU board
Relocating the 3xAA battery pack from the MPU board is always a good idea. Leaky alkaline batteries are the #1 killer of MPU boards. Simply removing the batteries is not an option with WPC games as a message stating "Factory Settings Restored" will be received when the game boots.
There are several options other than allowing the battery pack to remain on the MPU board. Below are the two most common methods.
The first, most common, and most economical option is to remotely locate the battery holder off the MPU board and somewhere below all other boards. This ensures that even if the remotely located batteries leak, they won't leak onto (or even drip onto) any circuit board. Replace the batteries annually, dating them with a Sharpie. Connections are as follows. With the CPU oriented as it would be in the game, solder the red (positive) wire to the upper right battery pack position. Solder the black (negative) wire to the lower left battery pack position. Note: most battery packs do not come with wire leads long enough to allow the battery pack to rest in the backbox bottom. Lengthen the wires as necessary. As can be viewed in the adjacent picture, a male / female .093" Molex connector was added to easily remove the battery pack from the MPU board should the need arise.
- WPC, WPC-S, and WPC-95 Remote Battery Holder Connections.
WPC-089 
WPC-S 
WPC-95
6.13.2 Installing an external battery on a WPC-95 CPU using the Auxiliary Battery header (J213)
The WPC-95 CPU board has an unused external battery connector just above the battery holder. The connector is labeled J213 AUX BAT. The 4 pads can be seen in the above picture of the CPU with the old holder removed. Installing this 4-pin connector is a good and clean way to get the batteries off the board and prevent alkaline damage. The Molex part number for the C-Grid® SL™ 70543 4 pin connector is 70543-003 (Digikey WM4802-ND). Crimp pins for the female side are 16-02-1125 (WM2573-ND) and the housing is 50-57-9404 (WM2902-ND). The WPC-S CPU uses a 5 pin version of this connector.
Warning: Do not use both the internal and external connector at the same time. Doing so will likely damage the batteries.
6.13.3 Settings Not Held or Battery Depletes Rapidly
During the process of installing a remote battery holder, it is a good practice to check the diodes utilized in conjunction with the battery power. Diode D2, a 1N4148, is used to keep the MPU board's logic power from charging the batteries in the battery pack. Diode D1, a 1N5817, is used to keep the battery pack from powering the entire MPU board when the games's power is turned off.
- If D2 fails shorted, 5VDC power will be applied to the batteries while the game is turned on. The end result is batteries which die prematurely, possibly leak, and/or possibly explode (alkaline batteries do not like to be charged).
- If D2 fails open, the batteries will not power the static RAM, and the "FACTORY SETTINGS RESTORED" message will be displayed when the game boots.
- Should D1 fail, the batteries would more than likely just deplete prematurely.
Testing to see if battery backup power is reaching the RAM with sufficient voltage is easy.
- Set your DMM to DC Voltage
- Connect the black probe to game ground (in the picture at left, a clip lead is attached to the ground screw)
- Use the red lead to probe pin 28 of the RAM
Measuring in this way should yield over 3.5 VDC. If measuring shows 0 VDC, either the batteries are dead, or D2 has failed (see above).
Ideally, this measurement should yield 1.5 VDC * 3 - .6 VDC = 3.9 VDC. This calculation represents the nominal voltage delivered by a single AA battery, times 3 (batteries), less a typical .6 VDC drop across diode D2. Remember that nominal voltage drop across a typical diode is .5 to .7 VDC.
6.14 Replacing the CPU RAM with non-volatile RAM
A second option is to replace the 6264 static RAM with an NVRAM such as the RAMTRON FM1608 (or FM16W08). NVRAMs in the standard DIP package are becoming hard to find but several pinball parts vendors sell a nice 6264 replacement NVRAM based on these parts.
This method requires desoldering the OEM RAM from the board, and installing a socket on the MPU. Using NVRAM also has the down-side of not maintaining the Real Time Clock. This is meaningless in some games. But some games use the Real Time Clock, like Twilight Zone which moves the playfield clock to the current time of day during attract mode, and Who?Dunnit and Junk Yard which has a "Midnight Madness" feature. Note: the WPC MPU is designed to accept either a 6264 or a 62256 static RAM. See: Jumpers, RAM and ROM size for a description of jumpers required when installing a new RAM or NVRAM. It is known that a Ramtron FM1608 chip does not like the voltage to be lower than 4.5V. With a voltage drop of 0.5V across D1, a jumper wire over D1 would be a solution to this problem. You can also just replace the diode D1 with a jumper wire. On a WPC-95 CPU-board you have the option to add W5 in stead of the jumper wire for D1. The result is the same.
6.14.1 Special note Concerning Early RottenDog WPC-TH MPUs and NVRAM
Most RottenDog MPU boards shipped with a 62256 RAM installed vs the 6264 RAM typically installed in Williams OEM boards. Early versions of the RottenDog board marked with "0701" on the silkscreen, as pictured at right, require the use of a 62256 NVRAM. The reason for this is that the address lines to the RAM position are not JEDEC "standard". Pins 9 and 10 (normally A0 and A1) are tied to ground as can be seen in the image at left. Clearly this scheme will not work with a standard 6264 pinout. But with a 62256, which has two extra address lines mapped as they are on the RottenDog board, will work perfectly fine.
A RottenDog WPC-TH OEM installed 62256 RAM
The RottenDog WPC-TH MPU RAM position. Note connection between pins 9, 10, and 14 (ground), which corresponds to the Cypress 62256 RAM pinout.
The pinout of the Cypress 62256 RAM, which matches the PCB design of the WPC-TH board
6.15 Repairing Alkaline Corrosion
Alkaline damage abatement on WPC MPUs is generally more difficult than Bally -17/-35 or Stern MPU-100/200 or Gottlieb System 80 MPUs. The traces on WPC MPUs are finer, and more abundant than on any of those boards. And, the "banks" of resistors and ceramic capacitors below the ULN-2803 and LM339s provide numerous hiding places for alkaline damage. The small traces under these components implement the switch matrix on the game.
If alkaline abatement is attempted, and if the ULN-2803 or LM339s are damaged, using any technique other than cutting them off the board, heating the alkaline damaged pads, and pulling the leftover legs out, WILL damage the board further. The alkaline adheres to the component legs and through-holes very strongly, making it near impossible to remove the component using typical desoldering tools, no matter how skilled the individual is.
As is normally done during this process, sand with fine grit sandpaper (or use an abrasive stick as shown on the right for precision work) until bare copper can be seen, treat the board with 50/50 white vinegar/water to neutralize the alkaline, then rinse thoroughly with isopropyl alcohol or other favorite cleaner. Re-tin the exposed traces.
- Replacing an Alkaline Corroded LM339 on a WPC-089 MPU
A corroded LM339 
After cutting one side off, then bending repeatedly to break the other side off 
Socket installed. All done
The RottenDog WPC-089 MPU board pictured at left is an extreme example of corrosion creep. Corrosion moved all the way up the remote battery holder wires and onto the MPU. Abating alkaline corrosion on RottenDog MPUs is particularly difficult as the traces and vias are very, very small.
WPC-089 MPU Alkaline Corrosion Zone
Part identification in the WPC-089 MPU corrosion zone.
WPC-95 MPU Alkaline Corrosion Zone
Williams located the batteries for the WPC-95 MPU in an even worse location than on WPC-089 and WPC-S boards. With the batteries located above the ASIC socket, there is a substantial probability that severe damage could occur from leaky batteries. The usual alkaline abatement process should be followed.
Key:
Resistors - Blue
Capacitors - Yellow
Diodes - Red
Integrated Circuits - Green
Headers/Jumpers - Black
Note that at least two revisions of the WPC-95 MPU board were produced, each with a slightly different part layout.
6.16 Slam Tilt
WPC games incorporate a slam tilt switch on the back side of the coin door. When closed, the game immediately stops, and the display fills with diagonal lines, as pictured at left. Note that this is not a power problem like a "game reset", below.
6.17 Stuck Menu Settings (WPC-95)
- Clear all the audits and reset to factory defaults.
- If using a battery for the RAM, remove/disconnect the batteries for a few minutes. Power up and check the settings to verify whether or not settings have become unstuck, then power off and reconnect the batteries.
6.17.1 Stuck Language Setting (WPC-95)
If the MPU language can't be changed via the settings menu, it is possible that the DIP switch bank has failed.
- Be sure that the DIP switch language switches are set correctly as detailed in the table at right.
- Ensure that a DIP switch hasn't failed by buzzing for continuity across a closed switch.
- Use test T.15, "Dip Switch Test", to ensure that the MPU is reading the switches correctly. If the physical DIP switch settings do not match the T.15 test indications, then either the DIP switch has failed, or U11, a 74LS240, has failed.
If there is a bad flipper opto board, this may also cause the language to get stuck (possibly in Spanish) and prevent the language from being changed in the menu settings or by using the MPU's DIP switches. Be sure to replace/repair the bad flipper opto board, then the language should then be able to be changed (Discussion on Pinside)
6.18 Power Problems with the RottenDog aftermarket power/driver board
6.18.1 Fuse Clips
The fuse clips used on the popular RottenDog aftermarket power/driver boards are a bit brittle and do not snap back into position if too much bending force is applied to them, much like Data East power supply fuse clips. Once the fuse clip has been bent too much, it will not snap back into position to create a solid mechanical connection to the fuse. This can cause one of the various power voltages to be missing or intermittent.
6.18.2 5V Regulator
Since the LM323K 5V regulator has been obsolete for many years, RottenDog Power/Driver boards were designed to use a DC-to-DC converter manufactured by Texas Instruments, part number PTR08060WVD. The part can be found here and possibly at other vendors.
Note: This part is installed on a RottenDog Power/Driver board with the inductor (copper coil) facing the top of the board. Equivalently, pin 1 of the device should be installed into the left-most PCB through-hole.
6.19 Game resets
One of the more annoying faults exhibited by WPC machines is the chronic reset problem. The game will restart, often when both flippers are used at the same time. Note that game resets are a power issue. "Slam Tilts" are something completely different (see above).
There are several possible reasons for game resets. Before doing any work on the circuit boards, it is recommended that a number of much easier to fix, and just as probable root causes, be examined.
Possible causes are listed below, in the recommended order of examination. This order is a derived from a combination of "ease of examination" crossed with "probability of root cause". The standard advice dispensed on RGP to change BR2 and C5 is often wrong and unnecessary. If BR2/C5 are changed out and the game no longer resets, some will conclude that, sure enough, BR2/C5 was the problem. What is being missed is that along with replacing those components, at the very least, the connectors on the board are being reseated, the solder on the cap and bridge is being reflowed, and the board ground to the backplane is perhaps better due to torquing the screws better. Any of these changes can improve voltage/current enough to reduce the frequency or eliminate resets.
6.19.1 The "Replace BR2 and C5 Mantra"
And now, a word on the classic "BR2/C5 mantra".
A long time ago…in a pinball galaxy far, far away…a kindly fellow was playing a nice game of pinball, hitting all the shots, and earning multiball after multiball. Just as he was about to beat the game’s high score to date, the WPC game MPU reset. "Not-A-Finga" he yelled in some ancient, dead, language.
A visitor from the neighboring planetary system noted that, "I once fixed that by replacing BR2 and C5". And lo, the mantra was born.
Fortunately, through advances in both our knowledge of these game systems, and the application of clearer thinking, we’ve come to realize that leaping to the “solution” of replacing components before doing real testing is not advisable. Most pinball owners do not possess the skill, experience, and tools that would allow them to work on circuit boards without damaging an expensive, and sometimes irreplaceable board.
Still, with regular frequency, a post will be read on RGP or PinSide that goes something like this…"My game was resetting so I replaced BR2 and C5 and the resets vanished." This logical construct is known as "Post hoc, ergo propter hoc" (after this, therefore because of this), an insidious logical fallacy that states "Since that event followed this one, then that event must have been caused by this one". Clearly, this is an invalid assumption. The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule out the connection.
In reality of course, when components are removed and replaced on a circuit board, the attendant "changes" to the state of the game system include…
- reseating connectors and possibly improving electrical conductivity
- possibly changing the connectivity through fractured solder joints which may be flexed differently
- reseating the entire board in the backbox and possibly improving ground for the board
- reflowing solder joints on both components possibly improving electrical conductivity
- possibly improving heat dissipation from the bridge to the heat sink by replacing thermal grease
- perhaps an air conditioner, refrigerator, or heater has shut off thereby increasing available electrical current
So please, hold off on heating up the soldering iron until methodically working through the disciplined process in the following section.
6.19.2 WPC 5VDC Power Derivation Path
Following is the nominal path from the wall plug to eventual consumers of the clean 5VDC power supplied by the Power/Driver board.
- 120VAC/60Hz power is nominally provided at the wall plug. Different voltages are accommodated also (see below)
- An RFI (radio frequency interference) filter, which is seldom a contributor to game problems.
- Line power is connected to a service outlet sometimes incorporated into the metal "power box" and made available to the tech via a short, uniquely plugged, extension cord. Line power is wired in parallel and does not require the power switch to be in the ON position.
- Both sides of the AC power pass through the double pole/double throw (DPDT) game power switch
- The "black" side of the AC power passes through an 8A FB fuse housed in a bayonet style (screw in) fuse enclosure.
- The "black" side of the AC power then passes through the thermistor, which limits current inrush into the system.
- "Butterfly" voltage select connector used to accommodate typical voltage systems used around the world (120VAC in US, 230VAC abroad, low line voltage, etc). When configured for 120VAC in the US, the connector and wiring resemble a butterfly.
- Transformer Primary windings
- Transformer Secondary windings
- Yet another Molex connector, mating with the harness that will eventually lead to the Power/Driver board.
- Some games incorporate a "coin door interlock switch" which interrupts coil and flasher power when the coin door is open. If the game is equipped with this switch, there will be an extra Molex connector necessary to implement this switch.
- J101 on the Power/Driver board (WPC-95: J129)
- Full Wave AC rectification and smoothing via BR2 and C5 (WPC-95: D7 through D10 and C9)
- Regulation to 5VDC via the LM323K at Q1 (WPC-95: LM317 at Q1))
- Lighting LED4... (WPC-95: LED101)
- And finally, delivery to 5VDC power consumers via J114, J116, J117, and J118 (WPC-95: J101, J138, J140, and J141)
Note that the LM317 is an adjustable voltage regulator where the LM323K is a 5V specific regulator. The LM317 is "programmed" to 5.108V using precision resistors R1 (750 ohms) and R2 (243 ohms), located just to the right of the LM317 heat sink. It is possible, although not advised, to adjust the output of the LM317 regulator to something other than the nominal 5.108 volts.
6.19.3 Possibly Skip Steps
If the game is resetting only within the first minute or two, and plays fine after that, skip to Step 8, Failed Thermistor. If the thermistor turns out to not be the cause, return to step 1.
6.19.4 The "Quick" but Temporary "Fix"
A quick but temporary fix might be to reseat (remove and then reinstall) J101 and J114 on the Power/Driver board and J210 on the MPU board several times. This might help in two ways.
First, the tarnish that builds up on the male/female connections might be removed slightly. This might be enough to return your game to service quickly. But this is not a long term repair. The proper repair is to repin both the male and female sides of the connectors.
Second, the physical point where the male/female pins meet becomes "welded" over time. That is, the pins develop micro-divots or irregularities that detract from a perfect connection. Reseating the connection may smooth out the defects that have formed and also might move the physical point of contact to a different part of the pins.
Again, reseating these connectors is a temporary fix that might work for a day, a week, or a month.
A Youtube video of this procedure being performed on a Bram Stoker's Dracula can be found here.
6.19.5 Low Line Voltage
Step 1: measure line voltage
Low line voltage can occur for several different reasons...
- Peak summer usage may cause a drop in line voltage (at the wall). Nominal voltage should be 115VAC minimum.
- Too many games or "power hungry" devices on the same circuit. This is common when numerous devices are plugged into a power strip.
- Game(s) plugged into an extension cord or power strip with too small of wire gauge. If the game is plugged into an extension cord, make sure that it carries all three conductors and is constructed of at least 16 gauge wire, or specified as 16/3. Using a beefier 14/3 extension cord is better, and advised if more than one game is plugged into the cord.
If the machine is resetting, open the coin door and measure the AC voltage at the auxiliary socket with the machine turned off, and then with the machine turned on. If the voltage at the auxiliary socket is over 105VAC, the problem is most likely inside the game. If the voltage is below 105VAC, there is a line voltage problem and the local electricity company's help will be needed to correct the problem.
6.19.6 Poor Ground Connection for Power/Driver Board
Step 2: Make sure the power/driver board is screwed down tightly
A poor ground connection from the power/driver board to the backbox ground plane can reduce 5VDC by as much as .3 volts. Ensure that the screws that hold the power/driver board down, secure it tightly.
6.19.7 Cracked Power or Ground Header Pins and Cracked Solder Joints at the 5V Fuse
Step 3: Examine the header pins at J101, J102, and J103 as well as at the LM323K regulator (WPC-95: J136 and J137)
Similar to step 2 above, cracked header pins where the power enters the board or at the ground connections on the board can cause game resets. In the picture at left, cracked header pins at J103 (ground) in a Twilight Zone caused game resets. Either reflow the solder, or better yet, replace the headers with new pins.
Another place to examine for fractured solder joints is on the solder side of the board, where the LM323K (WPC-95: LM317) 5VDC regulator is placed. This area is subjected to very high temperatures that sometimes causes the solder to crystallize. If the solder joint is in any way suspect, remove the old solder and reflow new solder on the joint. Ensure that a nice solder "meniscus" is created (a volcano shaped solder joint) versus a "doughnut" around the wire lead.
Fuse F113 (WPC-95: F105) fuses the 5V power for the game. Fractured solder joints here may cause the DMM to read near 5V, yet the joint doesn't allow enough current to pass. This can cause game resets and even cause the game to not boot. Reflowing the solder at these joints is prudent.
6.19.8 Missing diodes, open diodes, or cold solder joints at the Flipper coils
Step 4: Examine flipper coil diodes
WPC flippers are, in general, the only coils in the game that should have diodes across the coil lugs. While diodes seldom fail, sometimes the pounding environment that flipper diodes must live within causes solder joints to fail. Ensure that each flipper coil has the required two diodes, that the diodes are good, and that they are soldered to the coil lugs with a quality solder joint.
6.19.9 Poor Connections between the Transformer Secondary and the Power/Driver Board
Step 5: Examine the "cube shaped" molex connector in the cabinet
The connections from the transformer secondary to the Power/Driver board can degrade over time, a natural result of hours and hours of "power on" time. Try re-seating each connector. If the reset frequency is reduced or disappears, then the root cause has probably discovered. These connectors should be repinned at a minimum with at least new pins (the connector housings may be salvageable) for a long term solution. It is especially important to re-pin the red 9VAC wires that carry power to the Power/Driver board as this is converted to the 5VDC logic voltage.
Note: the molex pin extractor for these "round" pins is relatively expensive but there is no other good way to remove the pins.
6.19.10 Poor Connection at J101 on the Power/Driver Board
"Step 5.5: Examine both male and female connectors at J101 (WPC-95: J129)"
J101 (WPC-95: J129) connects the transformer secondary supply of both 9VAC (solid colored red wires, ultimately used to create 5VDC power) and 13VAC to the power/driver board. This connector often becomes tarnished, increasing resistance and reducing the effectiveness of the circuit. Reseating the connector may temporarily reduce reset frequency. This is an indication that this connector should be repinned. As always, it's best to repin both the male and female connectors.
6.19.11 Poor Connections between the Power/Driver board, the CPU, and other PCBs
Step 6: Examine other wiring harnesses and the connectors
Measure DC voltage at TP2 (WPC-95: TP101) on the Power/Driver board.
- DMM set to DC volts (if not an auto-ranging meter, expect to measure 5VDC)
- Black lead secured to game ground (the ground braid in the head is a good place to pick up ground)
- Red lead on TP2 (WPC-95: TP101). Remember the reading.
Measure DC voltage at the CPU board.
- Again, DMM set to DC volts
- Black lead in the same place
- Red lead on pin 32 of the game ROM, or on pin 2 (center pin) of the MC34064 under voltage watchdog at U10
- Record this reading
Compare the two readings. ANY difference indicates voltage loss between J114 on the power/driver board and J210 on the MPU board. Some voltage loss is expected/natural since no circuit path can provide zero resistance. A difference of .1VDC is enough to warrant examination of the connectors between J114 (WPC-95: J105) on the Power/Driver board and J210 on the CPU board.
Reseating the wire harness that connects the power-driver board to the CPU board may identify the root cause (but reseating is not a long term solution).
Some games use an interceptor harness to power extra boards (IJ, TZ, WH20, STTNG, FT, etc). There is a inline splice connector (commonly called a Z-connector) between the driver board and the CPU board. The Z-connector can become loose and/or oxidized, contributing to a poor electrical connection between the female connectors. The Z-connector can be replaced with a new one, or more robustly, eliminated by splicing the wires together, soldering, and heat-shrinking. This entirely removes the Z-connector as a contributing factor to game resets.
At least on Twilight Zone, the wire harness that contains the "Z" connector can be removed from the game entirely, as shown at right. This harness has been repinned and the "Z" connector eliminated.
Some field techs will "repunch" IDC connectors in an attempt to make a better connection. Without the correct punch tool, sometimes an even worse connection is created, as pictured at left. If the decision is to use IDC connectors, at least use the correct tool to punch the wires.
Tarnished, heat damaged, or damage to header pin plating creates resistance and can sometimes be a contributor to game resets. If the male header pins are tarnished, their female mates are probably tarnished also. If tarnished pins are found, now might be a good time to remove that aspect as a contributor to game resets.
If following this step-by-step process, now is the first time that a soldering/desoldering station will be needed.
Replace the male header pins, remembering to clip the correct "key" pin before reinstalling the board into the game.
Replace the female connector and pins with good quality Trifurcon crimp-on pins. IDC (Insulation Displacement Connectors) connectors as found originally on the game were used by the OEM to speed the manufacturing process and do not provide the level of robustness that can be achieved using Trifurcon crimp-on pins and good technique.
Another possible contributor to poor power connections is cracked header pin solder joints. Although, with WPC double-sided PCBs and the relatively large header pin through-holes, this is rarely seen. Should you identify cracked header pin solder joints, it's best to remove as much of the old solder as possible before reflowing new solder at the joint.
Be sure to check the power connections on the display as well. One documented repair involved a Funhouse with a reset issue. The game had a strong +5V signal on the MPU/CPU, a new BR2/C5 and digital voltage regulator. It would play perfectly until someone nudged the machine causing it to reset. During troubleshooting, it was noted that the game would reset (even in attract mode) when the display was lifted out of the backbox or placed back in it. It was then observed that the 2 wire/3 pin power connector had a loose IDC connection. The ground short through vibration was resetting the CPU! Repinning both the male and female ends of this connector with a proper molex housing resolved the issue.
6.19.12 Using a Multimeter to Test the Bridge Rectifier and Capacitors
Step 7: Bridges and Caps in circuit
There's one last test we can do before disassembling parts of the machine. This test can clearly identify a bad bridge rectifier or capacitor. You will need a clip lead.
- With the machine off, clip the lead onto the top left lead (positive) of BR2. You will have to do this by feel, as you cannot see the lead. This clip point is the output of the bridge rectifier, and is connected to the smoothing (filter) capacitor and LM323K regulator input. It should be at 9V DC.
- Next, place the other clip on the red (+) lead of your meter.
- Connect the black lead to ground by tucking it under the braid. Check your installation to make sure that nothing is shorting.
- Set your meter to DC volts.
- Turn on the game.
The meter should read about 9V. This will be true whether C4/C5 are working or not. If the bridge rectifier is bad, it will read about 7V.
For the capacitor, turn your meter to AC volts. Note that inexpensive meters may give false readings here. Ideally, your meter should be a true RMS meter. Good capacitors will read about 300mV AC. Bad capacitors will read up to 2VAC. Anything over 1VAC indicates a failed/failing filter capacitor at C5 which should be replaced.
6.19.13 Failed Thermistor
Step 8: Examine the Thermistor
The thermistor is (generally) a black or grey disk, about the size of a dime. It is located inside the power box which is found just inside the coin door and to the right. If your game has one (and not all WPC games do), it will be connected in series between the power box fuse and the black side of AC power. Note that the power box may also contain a "varistor", or MOV, which is essentially a surge protector. The varistor will be wired in parallel with (across) the AC power. The varistor is not a factor in game resets.
The thermistor's job is to limit current inrush into the capacitors when the game is first powered on. This reduces stress on the bridge rectifiers or diodes in the game's power circuits (which is the primary cause of bridge rectifier failures). After a few seconds, the thermistor heats up and drops to a very low resistance. Failing thermistors pass less current and have to get hotter to work. This heating takes time, so the game will often reset in the first 30 minutes of operation, and then be fine afterwards. Obviously, a cold environment will make the symptoms worse, and a warm room may appear to cure the problem.
Resetting while the game warms up is therefore a key indicator of a failing thermistor. Note also that DCS and WPC-95 A/V boards may reset independent of the MPU. If this is the case, you'll hear the characteristic same "bong" as when the game boots.
***Safety Warning*** Unplug the game AND turn the game off before conducting the following test.
Sometimes, the thermistor may be visibly damaged. However, it may look good and still be bad. An easy test of the thermistor is to jumper across the legs of the thermistor with a heavy gauge wire. If the game resets no longer occur, replace the thermistor with the correctly rated part. The original Williams part number is 5016-12978-00. A replacement is available from Great Plains Electronics.
While you have the box open try wiggling the connectors (the game IS unplugged!) you probably will find at least one that is loose - this can contribute to reset issues. The fix is to solder all the crimp quick connect (examples on coil) wires to the pins they were connected to in the box: cut the quick connects off, one at a time, and then solder the wires directly. Insulate the connections with Heat-Shrink or a good grade of electrical tape.
6.19.14 Questionable Prior Rework
Step 9: Examine prior rework
The printed circuit boards used in pinball machines sometimes have traces on both sides of the board. Most WPC boards are manufactured in this way. The traces are joined through the board by a thin layer of copper, plated to the inside of the hole. This plating is delicate. Without great care, the plating can pull out or crack when components are removed, especially alkaline damaged components as found on MPU boards (after batteries have leaked) and "snap caps" as found on OEM WPC Power/Driver boards (at C5 for instance).
Extreme care as well as good technique must be exercised when removing these components as it is very easy to lift traces or damage through-holes on the board. If the component is known to be bad, it is sometimes easier to snip the component from the board with a flush cutter and remove each leg of the component individually.
An excellent way to repair a lifted trace or cracked through-hole is to create a solder stitch between the traces on each side of a two sided board. Some PCB repairmen will install jumpers as a "repair" for cracked through-holes or to "guarantee" connectivity between components. Some PCB repairmen will avoid the use of jumpers in favor of better looking rework.
6.19.15 Failed Capacitors
Step 10: Power smoothing capacitors at end of life
Electrolytic capacitors do not last forever. They are designed to operate for about 1,000 hours at their full rating. Capacitor life is a function of temperature: the cooler the capacitor operates, the longer the life. The system designer must select higher voltage and capacitance ratings to achieve the design life, which can be as short as 5 years in a pinball machine operated continuously in a warm environment.
The WPC Power/Driver board uses a 15,000µF, 25V capacitor at C5 to smooth the full wave rectified AC from BR2. When this capacitor is no longer smoothing the rectified AC well enough to produce a clean 5VDC, the voltage may drop below the threshold enforced by the watchdog circuit on the MPU (an MC34064 at U10). When this happens, resets sometimes result.
Note that commonly available replacement capacitors are rated to 35V, and will work fine for this application. In general, you may use a capacitor rated for higher operating voltages but the capacitance specification (µF, or micro-farads) should not be changed.
C4 (spec'd at 100µF, 10V, axial) can sometimes fail and cause the game to reset also. If you've gotten this far and are replacing C5, you might as well replace C4 too.
Removing the big 15,000uf capacitors on a WPC-089 power/driver board is a bit tricky. More often than not, an amateur will damage the through hole that connects one side of the board to the other, either severing the connection completely, or badly enough to cause intermittent reset issues. Should the through hole be pulled, a solder stitch needs to be installed, or "jumpers" need to be installed connecting the associated bridge rectifier to the capacitor.
Advice: Without the experience, tools, and technique to accomplish this task, most hobbyists would be well advised to send the board to a pro for rehab.
A video demonstrating an excellent technique for removing snap caps can be found here.
6.19.16 Failed Bridge Rectifier
Step 11: Test Bridge Rectifier #2 (BR2)
The thermistor protects the bridge rectifiers from inrush current. Still, bridge rectifiers will occasionally fail.
Testing a bridge rectifier is simple.
The picture at left illustrates the 4 readings to be taken when testing a bridge rectifier.
Procedure:
- Place your DMM into "diode test".
- Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
- Place the red lead of the DMM on each of the adjacent legs, one at a time.
- A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
- Swap locations of the red and black leads. A reading of "null" should be seen.
- Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge
- Place the black lead of the DMM on each of the adjacent legs, one at a time.
- Again, a nominal reading between .5 and .7 should be seen.
- Swap locations of the red and black leads. A reading of "null" should be seen.
Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).
A video demonstrating the procedure to test and properly replace a bridge rectifier can be found here.
Should you decide to replace the bridge, it is best to screw the heat sink to the bridge before soldering it in place as the heat sink is shared between BR1 and BR2. A small amount of heat sink compound between the bridge and the heat sink is necessary. This compound improves conduction of the heat away from the bridge and into the sink.
Some repair tips suggested cutting the heat sink in half, separating it into two parts, one part for each bridge. This technique is no longer considered to be a best practice.
Solder both the top and bottom solder pads of the bridge. Should the through-hole of the bridge leads be cracked or otherwise damaged, use the "solder stitch" technique noted above or install jumper wires between the DC outputs of the bridge and the terminals of C5. When clipping the leads of the wire bridge, do not cut into the solder "meniscus" (the "volcano" of solder around the wire lead). Cutting into the solder meniscus can cause cracked solder joints later.
With proper desoldering tools, like the Hakko 808 or Hakko 470D, removal of bridge rectifiers and other components is greatly simplified. After replacement of bridge rectifiers is made, it's not a bad idea to mark the replacement date. In doing this, you or anyone else will know when these were replaced, and more importantly that they were replaced.
6.19.17 Failed Voltage Regulator
Step 11: When all else fails...
The LM323K 5V regulator is a robust device, but it can drift over time to below the design requirement of 4.8VDC. If your 5VDC reads less than 4.8VDC at the test point, or less than 4.75V on the CPU board, you have to replace the regulator. Note that these voltages are compliant to the LM323K's spec. However, at the lower end of this spec, this lower voltage may be the cause of resets.
If you decide to replace the LM323K regulator you may wish to consider using an EZ-SBC PSU5 instead. The PSU5 is a 5V 3A high-efficiency switch-mode regulator that is a direct replacement for the LM323K in terms of form factor and current capacity; it is superior to the LM323K due to its reduced power dissipation. When using the PSU5 be sure to replace the KEPS nuts (nuts with captive lock washers) originally used to mount the LM323K with discrete #6 split lock washers and #6-32 hex nuts; the external tooth lock washer of the KEPS nut can contact one of the surface-mounted components on the PSU5.
Note: The EZ-SBC PSU5 has one side affect that may be annoying. At power off, instead of the customary "pop", the speakers emit a loud volume "machine gun" or "fart" sound. While this might be unnerving, it is perfectly harmless. An updated version of the PSU5, identified by a yellow solder mask, does not have this side effect at power off. It is otherwise identical to the original PSU5.
An example of the sound can be heard here near the end of the video.
6.19.18 Failed Electrolytic Capacitor on the MPU
Step 12: Failed C31 on the MPU
There is one more possibility. C31 acts as a filter on the WPC-089 MPU. It is a 100µF, 10V capacitor, connected between incoming 5VDC and ground. Williams used two primary suppliers for this capacitor, Philips and Illinois Capacitor. If the capacitor is grey with black markings and has the logo "iC" on it, then it is from Illinois Capacitor and is likely ok. However, if the capacitor is blue and shows the manufacturer as Philips, you should replace it as it is most likely bad. The small Philips capacitors in particular have shown an increasing failure rate as these machines get older. This does not only apply to their use on the CPU but anywhere else in the machine. Which means the same rule applies to C4 on the power driver board - if it's a Philips capacitor replace it. If it's an iC capacitor it is likely OK. If you have a spare CPU, swapping the suspect one with a known working CPU is a good diagnostic step.
When replacing this capacitor it is best to use a 100uf 25v capacitor. You should note that by the time Williams got to the WPC-95 system, any place where they used to use a 100uf 10v filter capacitor they now had a 100uf 25v capacitor instead.
Determining whether or not C31 has failed is a challenge without an ESR meter. A simple visual inspection will not indicate whether the part is good or bad. Here are two C31s, one from a Funhouse and one from a BSD. Both of these are bad. Both should have an ESR reading of less than 2 ohms and a capacitance reading, out of circuit, of 100uf if not slightly more. Both the boards these were installed in would boot successfully on the bench hooked up to a dedicated power supply. Without an ESR meter, one might think these capacitors were fine. In fact, if this was the only thing wrong in the machine on the 5v circuit, chances are the game would operate fine with these capacitors as-is. But if the game is resetting, it is probably best to replace C31.
6.19.19 The Absolute Last Resort
Step 42: We really didn't want to get to this point!
There is a method of absolute last resort.
The LM323K is an adjustable linear regulator. However, Williams provided no means to adjust the output of the LM323K. As such, the LM323K will deliver a voltage anywhere within the spec range of the device. The spec output voltage range for the LM323K is 4.75 to 5.25 VDC. Some percentage of LM323Ks will fall into the lower range of that spec, which is at, or just above the trip point voltage of the MC34064 voltage watchdog on the MPU board.
The following procedure will increase the output voltage of the LM323K slightly. This procedure is not a substitute for addressing all of the considerations mentioned in previous steps, and should be used cautiously.
The LM323K draws a small current to operate, which it passes to ground. We can use that current to raise the voltage of the whole LM323K, pushing the output closer to 5V.
Procedure:
- Isolate the LM323K's metal case from board ground by cutting the ground traces that run left and right from the nut on the back of the board that bolts the LM323K to the board. The neater you make these cuts, the easier it to reverse this hack.
- Some versions of the Power/Driver board include a ground trace on the component side of the board that provides a ground to the tantalum capacitor at C9. This trace must be cut on the component side of the board.
- Add a 1/2W resistor in series, from the LM323K ground to the board's ground trace.
A 12 ohm resistor will nominally raise the LM323K voltage output by .1 VDC.
A 24 ohm resistor will nominally raise the LM323K voltage output by .2 VDC.
6.19.20 The Conductive Grease Hack
What is a "Hack"? Some techs will recommend the use of conductive grease to improve conductivity at a connector. While some techs will "swear by the stuff", other techs will "swear at the stuff", and as such, this is not considered a best practice. The grease can extend the life of new header pins, and protect against hostile environments that would cause corrosion. However, when used on header pins that are already damaged, grease can only slow further deterioration. Worse, the heat in the connector will turn the grease to gunk. If you find a flaky connector with gunk in it, you've been "greased" and you will want to re-pin it.
Damaged/burnt connectors should always be replaced. Dow Corning #4 grease can't help them.
On the other hand DC#4 Electrical Insulating Compound Grease does a superior job reducing friction and corrosion on contacts and that would be considered a net benefit to any game. JRR's shop and others have also found a decrease in the temperature of power contacts using DC#4 along with reduced resistance which should increase the life of the connector. This product is also good to use on EM pins for the interconnect plugs/sockets as it reduces friction and improves conductivity.
Note that DC#4 is stable from -57C to 204C (-70F to 399F). If your game has contacts at the high end of those temperatures then certainly, the smoke would be getting out...
If other products are used, investigate carefully to ensure they are a proper dielectric grease suitable for high temperature applications. There is a time and place to use this type of product, mostly as a preventative measure on newly replaced contact surfaces. Applying it after the plating has burned off is a questionable practice and no substitute for proper connector replacement.
6.20 Check fuses F114 and F115 message
This message is sometimes displayed when the game boots and a game cannot be started. Most of the time, F114/F115 will be found to be just fine.
The game issues this message because it cannot read the switch matrix normally. The crafty designers at Williams inserted an “always closed“ switch into the matrix as switch 24. Switch 24 isn’t a switch at all, but instead provides the game software with a “known closed” switch matrix return. Switch 24 is actually a diode across column 2, row 4 of the switch matrix and is located on the coin door interface board.
Since the WPC switch matrix circuitry on the MPU uses 12V to determine switch state, the game assumes that the 12VDC power has been interrupted. F114/F115 fuse the 12V generation circuit; F114 on the AC side of BR1; F115 on the DC side of BR1. Hence, the game assumes that one of these fuses is blown and the message is displayed.
Diagnosing the problem
Start by checking DC voltage at TP3. You should see about 12VDC. If not, follow these steps.
- Actually check fuses F114 and F115 using the procedure here. If a blown fuse is found, replace it. If F114 immediately blows again, then BR1 is probably shorted. Skip to the paragraph below to test the bridge.
- Check LED6. If not lit (indicating the absence of 18V at TP8), then suspect BR1 or the filter caps for BR1, C6 and C7. If BR1 had failed shorted or if C6 or C7 where shorted (rare) then you would expect to see F114 blown. BR1 can be tested using the procedure below.
- Check LED1. If not lit (indicating the absence of “digital” 12V at TP3, then test D1 and D2 (both 1N4004 diodes that can be tested with the game off or board removed using the standard "diode check" on your DMM).
- If D1/D2 test good, then check continuity from pin 2 of the 7812 voltage regulator at Q2 to J114, pin 5. This verifies the path to ground.
- Next, check continuity from pin 3 of the 7812 to J114, pin 2. This verifies the path through F115 to the 12V power header at J114.
- If this all checks out, yet 12VDC is still not at TP3, then suspect the 7812 voltage regulator at Q2. Q2 is in a TO-220 package (like a TIP-102) and has a small heat sink attached.
Alternate Problem Determination Method: Test Power Across the Driver Board
The diagram above shows the simple path for the 12VDC power regulation circuit. Power may be tested across the circuit, as follows.
- Turn the game on.
- Set your meter to DC volts. If your meter isn't an auto-ranging meter, expect to see less than 20VDC.
- Clip the black lead of your DMM to game ground, or tuck it under the backbox ground braid.
- Probe TP8 with the red lead of your DMM. It should measure about 18VDC. If not, suspect F114.
- Probe the banded side of D1. It should measure about 18 minus .5 to .7 volts, (the typical voltage drop across this kind of diode), or about 17.4VDC. If not, suspect D1.
- Probe the banded side of D2. It should measure about 17.4 minus .5 to .7 volts (again), or about 16.8VDC. If not, suspect D2.
- Probe the top leg of the 7812. It should measure about 16.8V. If not, suspect the trace between D2 and the 7812 or a fractured solder joint at the 7812.
- Probe the bottom leg of the 7812. It should measure about 12VDC since the job of this regulator is to produce 12VDC. If not, suspect the 7812 regulator.
- Probe the right side of fuse F115. It should measure about 12VDC. If not, suspect the trace between the lower leg of the 7812 and fuse F115. In particular, suspect that C2 has leaked and corroded the trace carrying the 12VDC. See: "Leaky Capacitor C2 corrodes trace", below.
- Probe the left side of fuse F115. Again it should measure about 12VDC. If not, suspect F115 is blown or the fuse block has a poor mechanical connection to the fuse or to the PCB.
- Finally, probe pin 2 of J114. It should read about 12VDC. If not, suspect the trace from fuse F115, the connection of the F115 fuse block to the PCB, or a fractured pin at J114.
The only circuit path remaining to test is the path to the ground pin of J114 (pins 5 and 7) from the 7812. This is easily accomplished with power off.
- Set your DMM to continuity and "buzz" between the tab of the 7812 to J114, pin 5 and 7. If no continuity, suspect a fractured solder joint at the center pin of the 7812, or corrosion under C2 that has compromised the trace.
Short on the MPU causing F115 to blow
There is one more way for the 12VDC power to be lost and for F115 to blow. A shorted IC on the MPU that uses 12VDC can cause F115 to blow. To help isolate the problem to the MPU, replace F115, disconnect power going to the MPU at J210, and turn power to the game on. If the fuse does not blow, the problem is almost definitely on the MPU board. Any of the LM339s (theoretically) or the ULN2803 (definitely) can fail and short 12V to ground, causing F115 to blow.
Leaky Capacitor C2 corrodes trace
Yet one more way for the 12VDC regulated power to be lost is shown in the picture at left. In the picture, the electrolytic cap at C2 has failed and leaked corrosive electrolytic contents onto the board. The lower trace from Q2 (7812 voltage regulator) to C2 (+ side), that goes on to connect to F115 on the solder side of the board, has been eaten away, no longer providing a path for the regulated 12VDC power. Corrective action here is the same as alkaline damage abatement.
Shown on the right is another shot of the damage caused by a leaky cap at C2. This one resulted in reducing the 12V power to about half of spec.
The corrosion resulting from a leaky cap at C2 can be quite extensive. Often, the parts immediately left of C2 are damaged and must be replaced. The part list is as follows, to be installed left to right:
- R206 - 27K ohm
- R198 - 10K ohm
- R199 - 1K ohm
- C1 - .001uf ceramic (or 1000pf, marked 102)
- R204 - 270 ohm
- C12 - .001uf ceramic (or 1000pf, marked 102)
- R205 - 270 ohm
- C3 - .33uf ceramic (not shown, located behind heat sink)
- D2 - 1N4004 (not shown, located behind heat sink)
Just a small fracture in the trace beneath the capacitor can cause a loss of 12VDC. The image at left was from a FishTales Power/Driver board.
If TP3 does, in fact, have 12VDC present, then we need to dig deeper.
- First check for 12VDC on the CPU board to ensure that the 12V is getting to the board via the 2 (and possibly 4 if your game has a “Z-Connector”) connectors that carry the 12VDC. An easy place to measure 12VDC on the CPU is at pin 10 of the ULN2803 (U20). Pin 10 is on the bottom row of pins, furthest left. Note that this connection (and also the 12VDC connection to pin 3 of the LM339s) is not shown on the schematic.
- If the CPU is receiving 12VDC, and you still have the “Check fuses F114 and F115” message, then the problem lies within the CPUs switch matrix logic circuitry.
- Prime candidates for CPU switch matrix failure are U20 (a ULN2803), the two LM339s at U18 and U19, the 74LS374 at U14, and the 74LS240 at U13. All of these ICs are in the “corrosion zone” caused by leaky alkaline batteries. If your CPU exhibits the “blue/green fuzzies”, address the alkaline damage first.
- Testing the 74LSXXX ICs is simple using the procedure here.
- If coil power, flasher power, or even lamp power was somehow shorted to the switch matrix, there is a near 100% probability that the ULN2803 at U20 has been damaged. There is no good way to test the ULN2803 other than using a logic probe with the game powered on. Both the input side and the output side of the ULN2803 should be toggling between logic 0 and logic 1. If not, socket and replace the ULN2803.
Testing a bridge rectifier is simple.
- Place your DMM into "diode test".
- Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
- Place the red lead of the DMM on each of the adjacent legs, one at a time.
- A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
- Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge.
- Place the black lead of the DMM on each of the adjacent legs, one at a time.
- Again, a nominal reading between .5 and .7 should be seen.
Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).
Testing BR1 "InSitu"
It is possible to test BR1 while the power/driver board is still installed in the game. Thanks to PinSider "Zaza" for the procedure and animation.
- Power the game off
- Ensure fuse F114 is good
- Remove connector J101 on the right side of the power/driver board
- Set your DMM to "diode check"
- Probe as indicated in the animated gif pictured below
Take special care when replacing a bridge rectifier. It is easy to lift the traces of the plated through holes when removing these. After removing the heat sink, cut the old bridge rectifier off of the board close to the top leaving as much of the lug as possible. Then add a small amount of solder to the connection on the solder side to improve heat transfer. Finally apply the iron to the solder side to heat the joint and remove the remaining lug with small pliers.
When replacing the new bridge rectifier you should remove the old thermal compound and apply a new thin layer. The old compound can be removed with a little rubbing alcohol. Apply the thermal compound to the top of the bridge rectifiers and reattach the heat sink with the screws (see above). It is much easier to replace the heat sink before resoldering the new bridge rectifier. Make sure that the heatsink is sitting flush with the tops of the bridge rectifiers and that you leave about a 5/8" gap between the bridge rectifier and the board to improve air flow.
Splitting the heat sink between BR1 and BR2 was at one time thought to improve reliability. This is no longer considered a best practice and is not recommended.
In WPC-95 games, BR1 and BR2 were replaced by a series of diodes. D11-D14 replaced BR1. D7-D10 replaced BR2. These are much less prone to failure. Still, they do fail on occasion. If one or more fail, it's best to replace all four in the "gang". These diodes were originally 6A2 diodes. Replace them with 6A4 diodes (6 amp 200V vs 6 amp 400V). See the "Check Fuses F106 and F101" section below for the equivalent WPC-95 message.
6.21 Check Fuses F115 and F116 Message
Similar to the "Check Fuses F114 and F115" above, games like Demolition Man will display this message at power up if the trough optos are seen as closed (remember, the opto switch open/closed logic is inverted). Debug this issue by checking the 12v connectors at the lower left corner of the driver board and the connectors on the trough opto transmitter and receiver board.
6.22 WPC-95 Check Fuses F106 and F101 Message
If a WPC-95 game detects loss of 12VDC power by not seeing switch 24 as closed, "Check Fuses F106 and F101" will be displayed at power up. This could obviously mean that F101 and/or F106 are blown. It might also indicate failure of the LM7812 12VDC regulator at Q2 in which case LED102 will be on and LED100 will be off or, failure of one or more of the 6A2 diodes that rectify the AC power (D11-D14). In the latter case, both LED102 and LED100 will be off. Use these LED indicators, as well as testing for 18VDC at TP102 and 12VDC at TP100 to guide your repairs.
6.23 Line Voltage Detection - LED2 & LED3
LED2 and LED3 on the Power Driver Board are indicators for the line voltage detection circuit. On on-board comparator circuit uses +5V and +18V to check the line voltage. The comparator consists of a resistor voltage divider and an LM339 comparator.
The following table shows how to interpret the LED states. Note that other problems with the +18V or +5V supply could cause a high or low line voltage indication.
Line Voltage Indicator Chart
| LED2 | LED3 | Voltage |
|---|---|---|
6.24 Exploding or Damaged 15,000uf Capacitor at C11 (C10 on WPC-95)
A smoking, domed, or in the worst case exploded filter capacitor at C11 can result from cross connecting J124 and J128 on the power/driver board. Doing so creates a circuit that routes 70VDC coil power through C11 which is typically rated at 25VDC and is meant to filter the 20VDC flash lamp circuit. This is made possible since J124 and J128 are identically implemented. Both are 5 pins wide, both keyed at pin 4. This is possible on WhiteWater, Dr. Who and Bram Stokers Dracula at least, and may also be possible on other games. It is possible on any WPC or WPC-S game that uses J124, whether or not J128 is used.
Another very effective way to blow C11 is to connect the flash lamp power connector at J106 to high power coil grounding circuits at J132. The connectors are the same width and keyed identically. This connects 72VDC coil power to the 20VDC flash lamp power which is filtered by C11, a 15,000uf/25V capacitor, with the same results as mentioned above.
Other possible causes for a damaged C11 are a shorted flipper coil diode, a shorted drive transistor on the FlipTronics board, or installing backbox ribbon connectors incorrectly (bottom female housing row to top male header row).
An effective method of preventing damage to C11 in the event that one of the conditions above is met, is to install a blocking diode in series with the large sand resistor at R224. Install a 1N4004 (for example) with the banded side facing the PCB as pictured at left.
6.25 WPC and WPC-S Games With No Solenoid, Flasher or Feature Lamps, A Blanking Signal Issue
The blanking signal from the MPU is connected to pin 1 of each of the 74LS374 buffers (U1 thru U5 and U18) that drive general illumination, flash lamps, coils, and feature lamps. Normally, this signal is pulled low by the MPU board, indicating that no faults have been detected and the system is running as expected. Without a low blanking signal, none of the game features implemented by the driver board will be enabled.
As these games begin to age, the 12V filter cap located at C2 begins to leak it's corrosive contents onto the PCB. As noted in the section titled "Check Fuses F114 and F115 Message", the corrosion often damages adjacent parts and sometimes invades the solder mask to sever critical signals, like the blanking signal or even data signals. If continuity can not be "buzzed" between the blanking and data pins of U1 and U2, and C2 has been leaking, then there is a good chance that the signal trace has been severed under or around U1. Corrosion seems to accumulate under the chip and between the legs frequently. To address this issue, cleanly remove the chip, clean up the corrosion, rebuild traces as necessary, install a socket, and replace the 74LS374 if necessary.
The blanking signal on the MPU originates at the ASIC (pin 34). It is inverted 3 times by U21 and U5 before being distributed to J204, J211, J202 and the blanking LED. J211 connects via 34 pin ribbon to the power/driver board. If the blanking signal fails to reach J211 pin 31, the same behavior as described above will occur. A DMM set to continuity mode should indicate a connection between U5 pin 8 and J211 pin 31. Sometimes, the signal is interrupted by a damaged or poorly formed via, shown in the picture at right.
6.26 WPC Games With No Flashers
On WPC-89 games, if no flashers are working, and if the game uses a motor and that also isn't working (such as the cannon on T2), the problem might be somewhere along the secondary unregulated 12V path on the WPC driver board. It could be a connector issue, blown fuse, bridge failure, or detached bridge eyelets on the PCB.
- First, check the interlock switch (if applicable on your game) to make sure that it isn't disabling the voltage.
- On the driver board, check LED5. This is lit if 20VDC is present, if not, 20VDC (and 12VDC for the flashers/motors) is missing (or too low). If it is lit, then proceed to check R224 (10W resistor) for the correct resistor value (0.12 Ohms) and continuity for the legs.
- On the driver board, if LED5 is off, check fuse F111.
- Check TP7 to see what the reading for 20VDC actually is. If the reading is near zero, then:
- Check connector J102 for 20VAC on pins 1 and 3. If about 20VAC is present, the issue is likely on the driver board.
- Check the BR4 bridge rectifier using this guide. If the bridge is bad, replace it. If not, test for continuity:
- Test for continuity between the bridge legs and nearby connection points.
- For the negative leg, test to the negative leg of C11. Also check for continuity to J115 pin 1 or any pins on J103.
- For the positive leg, test to the positive leg of C11 and the leg of R224 (10W resistor).
- For the AC inputs, check the top/upper AC leg to J102 pin 1, and the lower/bottom leg to J102 pin 3.
- If there is a loss of continuity on one or more legs, it is possible that the eyelets separated from the traces. Only the positive leg has a trace on the back side, which helps anchor the eyelet, while the other three legs are more prone to separation since there are no traces on the back side to help anchor them. They can separate due to fatigue or prior repair work.
- Remove BR4. The easiest approach may be to clip off the bridge and then desolder each wire leg individually.
- There are two possible approaches--adding a wire stich on the top side of the PCB, or adding jumper wires on the back side of the PCB.
- To stitch: If possible, scrape a little bit of the mask off the affected traces, then add a wire stitch to the top side of the PCB from the exposed trace to the leg hole. Once done, install the bridge and solder the legs.
- Or to add jumpers: just install and solder the bridge, then add jumper wires for the appropriate failed eyelets using 18 gauge wire.
- For the negative leg, jumper it to the negative leg of C11.
- For the positive leg, jumper it to the positive leg of C11.
- For the bottom/lower AC leg, jumper it to J104 or J105 pin 4.
- For the top/upper AC leg, jumper it to J104 or J105 pin 5.
- If BR4 tests good, BR4 has continuity, LED5 is lit, TP7 has 20VDC, check R224 for 20VDC on one side and 12VDC on the other. Check for 12VDC at J107 pin 5 & 6, J106 pin 5, and J108 pin 3. Check for connector issues and cold/cracked solder joints at those pins.
6.27 Solenoid, Flasher, and Motor problems
Flashers, solenoids, and motors in WPC games are turned on via transistors on the driver board and in some games, transistors on the Auxiliary 8 Driver Board.
Before proceeding to diagnose solenoid or flasher problems, see this section: How Coils, Flashers, and Motors are Turned On.
The general logic for providing a path to ground for a coil, solenoid, flasher or motor (subsequently, we'll refer to coils only, but this is true for coils, flashers, and motors) via the driver board is as follows. Operation of the Auxiliary 8 Driver Board is similar but control is accomplished via the long ribbon cable from the MPU to the 8-Driver Board.
- The MPU places the appropriate bit pattern on the data bus to control a "bank" of 8 transistor circuits. The data bus is extended to the power/driver board via the interboard ribbon cable.
- The MPU/ASIC "clocks" the appropriate 74LS374, an "octal latch" on the power/driver board, to latch data on the data bus into the 74LS374.
- The outputs of the 74LS374 turn on a 2N5401 transistor.
- The output of the 2N5401 turns on a TIP-102 transistor.
- The TIP-102 transistor either provides the path to ground for the waiting coil power or, for higher powered coils, turns on a TIP-36c transistor which provides the path to ground.
The reason that (up to) 3 transistors are used in the circuit is to "amplify" the power. A 2N5401 transistor can handle a comparatively small amount of current. A TIP-102 transistor can handle a much greater current load. The TIP-36c in 8 of the WPC power/driver board circuits can handle an even greater current load.
Note: With the exception of flipper coils and coils driven through the "special solenoid" drivers, diodes used to snub the reverse current caused by the collapse of the coil's electromagnetic field, are located on the driver board. High power and low power playfield and backbox coils (solenoids 1 through 16) should not have a diode on them. This convention eases the tech's job in that he/she doesn't need to be careful with diode orientation on the coil.
Note: Coils driven by a Flash Lamp drive (solenoids 17 through 20) or by special solenoid drives (solenoids 21 through 28) require a "tie back diode" connection. When a flash lamp drive is used, a diode must be added to the circuitry, as was done with the Terminator 2 single drop target for example, as the power/driver board doesn't include this diode. When a special solenoid drive is used, a connection from the coil, back to the appropriate pin on the driver board which leads to the on-board tie back diode, must be made. See the section Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode below for more information
6.27.1 Transistor "Quick Check"
A quick check of the TIP-102s on the driver board can save time. Set your DMM to "continuity check". Place the black lead of your DMM on board ground. Touch the tab of each TIP-102. If the meter indicates continuity, then that TIP-102 is shorted. This quick test works only with TIP-102s and NOT with TIP-36c transistors since the tab of a TIP-36c is connected differently.
For WPC power/driver boards, the lamp matrix TIP-107 transistors can also be checked using this method if the black probe is touched to the 18V test point on the right edge of the board.
A video demonstrating this technique on a Data East MPU can be viewed here.
6.27.2 "Help" Info Provided by WPC Games
During coil test, pressing the credit button provides a bit of information helpful in debugging your game.
With coil test "stopped", pressing the credit button sequences through the following information.
- Solenoid power and ground (drive) wire colors
- Solenoid power and ground (drive) connections
- The fuse that protects the circuit
- The sequence of cascading transistors that provide a path to ground for the solenoid. In the picture at right, Q82 (TIP-36), Q81 (TIP-102), and Q71 (2N5401) provide the path to ground.
6.27.3 Failed TIP-36c
When replacing shorted transistors, examine the traces connected to the transistor for further damage. In the picture at left, a shorted TIP-36c was replaced. During test, the first time the TIP-36c was called upon to provide a path to ground for the associated coil, the TIP-36c failed shorted again. This was caused by the blown trace.
6.27.4 Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode
Several games (Star Trek the Next Generation, Funhouse, Terminator 2, Indiana Jones, and The Addams Family to name a few), employ the use of a "diode tieback" system on a specific coil or motor. A diode tieback is the use of a clamping diode between the drive transistor ground and the voltage source to accommodate the reverse voltage spike induced when a coil's magnetic field collapses. While Williams moved most clamping diodes to the power/driver board, the flashlamp circuits (drives 17 through 20) don't include a clamping diode. Flash lamps don't create the same reverse voltage spike and hence, don't require a clamping diode. A tieback diode must be added to the game wiring when one of these flashlamp drives are used to turn on a coil or a motor.
The "Special Solenoid" drive circuits (drives 21 through 28) do include a clamping diode but that diode isn't connected to a voltage source. Presumably, Williams did this to provide flexibility in voltage levels used to drive a special solenoid. When one of the special solenoid drives is used to drive a coil or motor, a connection must be made from the power side of the coil or motor back to the associated power/driver board clamping diode via the appropriate header pin at connectors J122 through J126.
If the tieback diode connection is lost, the associated drive transistor on the driver board (as pictured on the right) WILL be damaged. Also, the associated coil is likely to be held on continuously and melt. In the example pictured at left from a Terminator 2, the diode tieback wire is the thin violet/orange wire. It connects from the coil power side on the drop target assembly coil lug to J122 pin 9 on the driver board and then to clamping diode D5. If the solder connection at the coil lug is solid, suspect the wire connection at the J122 IDC connector. Repinning this connection with a good quality crimp-on Trifurcon pin is advised.
The Addams Family uses Q20 for the "Swamp Release" coil, Q22 for the "Bookcase Motor", Q24 for the "Thing Eject Hole", and Q26 for the "Thing Motor", all requiring a tieback diode.
Star Trek: the Next Generation drives the subway diverters via the 8-Driver board in the upper right side of the head. These also require a tieback diode as discussed here.
6.27.5 Coil Locks On
This is the most prevalent problem observed (versus coil not firing). When a coil locks on, this means that the power that is present at the coil at all times has found a path to ground. Normally, a path to ground is provided via a controlled transistor set on the driver board. In rare cases a frayed wire or a wire with an insulation gap/failure will touch ground and the coil will lock on.
Most of the time, the drive transistor on the driver board has shorted internally and is acting as if it's been turned on. Should this be the case, the following steps will isolate the problem transistor.
- Use the "Solenoid/Flasher Table" at the front of the game manual to identify the likely failed transistor(s).
- Remove the driver board from the game.
- Test the drive transistor (TIP-102 or TIP-36c).
Testing a TIP-102 transistor
- Set the DMM to diode check
- Place the black lead on the center leg
- Place the red lead on each of the flanking legs in turn
- A measurement between .5 and .7 should be displayed
- Readings outside of this range (generally dead shorts) indicate the part has failed.
Testing a TIP-36c transistor
A video showing how to test a TIP-36c can be found here.
- Set the DMM to diode check
- Place the red lead on the center leg
- Place the black lead on each of the flanking legs in turn
- A measurement between .5 and .7 should be displayed
- Readings outside of this range (generally dead shorts) indicate the part has failed.
If the drive transistor tests failed, remove the part using this procedure being very careful with the delicate traces and through holes.
Most of the time, the last transistor in the cascading transistor chain is the only one to have failed. But, it's important to test the upstream transistors before placing the board back into service. If a TIP-102 has been found to have failed, test the upstream associated 2N5401 predriver. If a TIP-36c has been found to have failed, test the upstream associated TIP-102 and 2N5401 predrivers.
Sometimes, additional parts connected to the failed transistor will have been damaged too, as pictured at left. It then becomes necessary to replace those parts, remove carbon (it's a conductor) and to rebuild burned traces as necessary.
When a coil has locked on for an extended period of time, the coil wire insulation heats up, melts, and begins to short together. Left locked on for long enough, the coil becomes a dead short. It's important to test the resistance of the failed coil to ensure that it hasn't been damaged. A resistance measurement less than 2 ohms certainly means that the coil is damaged, but comparing the coil's resistance to other known good coils is the best and easiest test. WARNING: If the coil has become a dead short and remains in circuit, and the game is powered on, the associated driver transistor WILL be damaged.
6.27.6 Coil Fails to Work
Before proceeding, see this section: How Coils, Flashers, and Motors are Turned On.
Possible causes for coils failing to fire include:
- The switch associated with the coil is not being sensed by the MPU, and hence the MPU doesn't command the coil to fire.
- The coil doesn't have power
- One/both of the coil wires are not solidly soldered to the solder lug
- The coil winding is open
- The coil power is not finding a path to ground
- Interlock switch is not activating when pressed
6.27.6.1 Associated Switch Failure
If the MPU isn't commanding the coil to fire, obviously it won't. For instance, if a slingshot switch isn't being "made" or some other switch matrix problem prevents proper switch sensing, then the MPU won't command the slingshot coil to fire. This type of failure is easy to isolate merely by placing the game in switch test and closing the switch. Also, if during game play, points are scored when the switch closes, clearly the switch is being made. If a coil fires in solenoid test but not in game play, then the root cause is a switch problem versus a coil problem.
6.27.6.2 No Power to the Coil, Coil Wire not Solidly Soldered, or Coil Winding Open
Testing for power to the coil is easy.
- Set the DMM to DC volts. If not an auto-ranging meter, expect less than 200VDC.
- Turn the game on.
- Place the black lead on a convenient game ground like the ground braid or side rail.
- Place the red lead on the coil lug with the "fat" wire(s). The fat wire carries power to the coil.
- The appropriate voltage should be read (75VDC for coils, 20VDC for flashers)
If the appropriate voltage is not seen, there are two primary reasons. Either the power circuit fuse has blown or there is a discontinuity in the power wiring from the driver board to the coil. Turn the game off. Remove the associated fuse and "buzz" it with a DMM set to continuity test. While the fuse is out of the board, make sure it's rated at the proper amperage. Generally, WPC coil and flasher circuits are fused with a 3ASB fuse. If the fuses tests good, the next test is to ensure continuity from that fuse to the coil power lug. With the DMM still set to continuity, "buzz" between the fuse and the coil power lug. If continuity isn't proven, the task is then to find the break in continuity between the driver board connector and the coil power lug. Remember that power is "daisy chained" through several coils in the game. That is why some coils will appear to have two power wires soldered to one lug.
If the appropriate voltage is seen, then test for a break in the coil windings. With the game still powered on...
- Place the red lead on the other coil lug.
- Again, the appropriate voltage should be seen.
If the appropriate voltage is not seen, then either the coil winding has a break in it or the winding is not solidly soldered to the coil's solder tabs.
6.27.6.3 Coil Power is Not Finding a Path to Ground
The smaller wire attached to one of the coil lugs connects the coil to the driver board. The driver board has a drive transistor allocated for each coil in the game. The smaller wire must have a solid connection back to the driver board. There are two ways to test the path to ground.
- Use a DMM set to continuity to "buzz" the connection of the smaller wire between the coil and the female connector on the driver board. Ensure that the connection of the wire at the IDC connector is solid. If the coil is driven by a TIP-102 transistor, buzzing between the smaller wire on the coil and the transistor tab should show continuity.
- With the game powered on, and a short length of wire stripped on both ends, touch one end of the wire to the ground braid in the head. Touch the other end of the wire BRIEFLY to the tab of the associated TIP-102. If the coil pulls in, then the path to ground has been proven and the failure is likely the TIP-102 itself. NOTE: This test can be performed ONLY when a TIP-102 is the drive transistor. TIP-36c transistors are configured differently. The tab of a TIP-36c is not connected in the same way.
Once the wiring and connector have been verified to be in order, the next step is to test the associated drive transistor. Unlike when a coil locks on and the driver transistor has shorted on, in this case the drive transistor may have failed "open". Test the transistor using the same procedure outlined in the prior section. Replace as necessary.
If the drive transistor tests failed, remove the part using this desoldering guide being very careful with the delicate traces and through holes.
6.27.6.4 High Voltage Interlock Switch Failure
On later WPC games (beginning sometime during production of Twilight Zone in 1993), there is a push button switch used for disabling high voltage circuits (20VDC and 50VDC) when the coin door is opened, providing a measure of safety against higher voltage shocks.
Sometimes, this interlock switch can get worn or dirty (or there are problems with the movement of the internal parts), and the switch doesn't always form a closed circuit properly. So, while the coin door is closed, the interlock switch may fail to activate the 20VDC and/or 50VDC circuits.
Note that there is a separate push button switch responsible for reporting to the MPU whether or not the coin door is open in order to display the "high voltage disabled" message. So, if the high voltage interlock switch fails to complete a high voltage circuit, the MPU will have no idea about this failure, and thus not display a notification message.
To test for the issue, turn the game off, and use a digital multimeter in continuity mode across the appropriate switch lugs for the two circuits (20VDC and 50VDC) on the interlock switch. If the lugs are dirty, they may need to be cleaned. If there is black gunk that looks like it may be baked onto the lugs, it may need to be sanded or filed off to reach the bare metal of the switch lug. Once the lugs are clean and the multimeter is attached, then slowly press in the switch button. If a switch closure is not detected, there may be a problem with one of the switch's circuits. If there is only a switch closure at a certain point where the button is only pressed part way, then fails again after being pushed all the way in, there is likely a problem with the internal parts of the switch.
The switch can be opened up and inspected for issues, and possibly cleaned and repaired. Or, it can simply be replaced with an E79-00A momentary switch or E79-30A0 momentary pull-on switch (both are DPDT, 10A, 125/250v).
6.27.7 Low Coil Voltage
Coil power for WPC games is nominally about 70VDC. Very little can reduce this voltage. If the game is delivering significantly less than 70VDC, suspect BR3.
It's also possible for C8 to cause reduced voltage. C8 is a 100uf/150V (sometimes installed as 100uf/100V) capacitor.
6.27.8 Q26 Transistor & Coil Locking On with Rottendog Driver Board
If the Q26 transistor (and associated coil) keeps locking on with a Rottendog WDB089 driver board, there may be an erroneously exposed trace on the back of the PCB near one of the screw mount notches that is causing a short. It is located at the bottom edge of the board near connector J122. The exposed trace is next to the grounding pad for the screw mount, and excess solder may be bridging them together.
The issue was noticed on a revision 2 board. It is not currently known if other board revisions are affected by the issue.
To address the issue, first remove any excess solder that may be bridging the connection between the exposed trace and the grounding pad. Then, seal the exposed trace with a PCB solder mask material (ie, an overcoat pen would work) or clear nail polish.
6.28 Lamp problems
Lamps (or globes for those of you in the UK) fall into two categories. "General Illumination" and "Controlled Lamps". Your game probably has other lamps which are actually "flashers" that require an 89 or 906 bulb. Flashers are covered elsewhere in this Wiki.
General illumination lamps (GI) provide the ambient lighting for the playfield, backbox, and coin door. These lamps are lit most of the time. The only "controllable" aspect of these lamps is their brightness, which of course, includes off.
Controlled lamps (sometimes called "feature lamps") are under complete CPU control via the 8-by-8 lamp matrix. These lamps illuminate the various "features" of the game such as mode inserts, pop bumper lamps, inlane/outlane insert lamps, etc.
6.28.1 General Lamp Problems
WPC and WPC-95 systems employed "lamp boards" to ease the manufacturing process. These lamp board PCBs used "twist in" sockets, each with a 555 lamp. Over time, the pads on these sockets develop "divots" which sometimes results in a poor connection to the twist in socket. This can be easily corrected by removing the lamp board from the game and reflowing the solder on the pads.
Another problem with lamp boards is the header connections. The solder joints at the connection pins often fracture due to connector insertion pressure, heat, fatigue, etc, and due to being a single sided PCB. The fix for this is again to reflow the solder around the header pins.
One of the less reliable designs Williams used was to "cantilever" lamp sockets over the end of lamp boards. This was done on a great many games such as Twilight Zone, Judge Dredd, etc. The repeated pressure needed to insert a new lamp into the socket causes the solder to fracture. This can be corrected easily by simply reflowing the solder at the joint.
However in some instances, the socket has become damaged beyond the simple repair of just soldering the legs to the lamp board. Replacement sockets are available from most pinball parts vendors.
If after repairing the lamp board divots, reflowing the header connectors, the lamp socket is still completely intact, (the contacts do break off of the socket sometimes), and the bulb is good, suspect that the diode associated with the particular lamp may be bad.
6.28.2 General Illumination Problems
Background
The WPC power/driver board provides 5 GI circuits under CPU "brightness control". The WPC-95 power/driver board provides 3 GI circuits under CPU "brightness" control and 2 circuits that are always powered. Those two circuits are always connected to the backbox lamps.
GI power is provided by the transformer in the form of 6.3VAC at power/driver board connector J115. Although there are five pairs of wires, they are all connected together at the transformer. One side of the AC GI circuit on the power/driver board is fused by F106 through F110 which are all 5ASB fuses. This side runs to the GI lamps, and carries 6.3VAC to the backbox, playfield, and coin door via power driver board connectors J120, J121, and J119 respectively. J119 is a 3-pin header that is always connected to the coin door lamps. J120 and J121 are electrically and physically identical (keyed at pin 4) and therefore can be connected to either the female playfield GI connector or the female backbox GI connector without care. The other side of the GI AC feed is connected to ground.
The GI power is controlled by a triac in the return line from the playfield. When these triacs are off, no current passes and the lamps are off. When the triac is turned on, the GI lamps glow. The triac is a slightly special part - it must be a "four sector" triac. This means that it can switch both positive and negative sides of the AC cycle with only a positive signal.
Each triac is switched on/off by a 2N5401 transistor which is controlled by U1, a 74LS374, an octal D-Type Flip-Flop with three state outputs (a fancy way of saying that the device is an 8-bit data buffer).
U1 is "clocked" by the ASIC via the /TRIAC signal. If you have AC power present at J115, and no GI at all, it's possible that the /TRIAC signal is not getting through to U1. A logic probe applied to pin 11 of U1 will prove that the signal is getting through. If the signal is not present, try (after turning the power OFF)...
- Pressing firmly on the MPU ASIC to "reseat" it.
- "Reseating" the ribbon cable between the MPU and the Power/Driver board.
- Use your logic probe to track the signal from pin 66 of the ASIC, across the MPU to the MPU connector, across the ribbon cable, then across the Power/Driver board to U1 pin 11.
The CPU can dim the GI by switching on the GI for only parts of the AC waveform. To do this, the CPU uses a zero crossing signal on the driver board keyed from the AC that feeds the 5V circuit, diodes D3 and D38, and the LM339 at U6.
A video further describing operation of the General Illumination circuit can be found here.
Wire colors to J115 during the early WPC games were always yellow (AC) and yellow-white (AC return) as pictured at left. Pin 1 of J115 provides the "ground reference". Later WPC games used different wire colors at J115 and instead of "looping" power through the connector at J115, connected two wires to the same pin at the 9-pin connector between the transformer secondary and J115 (note picture at right that implements the same concept for earlier model games.
The colored wire connections for this era of WPC game are yel-wht connected to pin 1, yellow connected to pins 2-6, yel-wht connected to pins 7,8, 10, 11, & 12. Pin 9 is the key.
J119 is always keyed at pin 2, with a white-Violet wire at pin 1 and a Violet wire at pin 3
J120 and J121 are 11 pin connectors. Wire color/positions (when used) are identical for all WPC games and are shown in the table.
| Wire color at J120/J121 | |
|---|---|
| Brown | |
| Orange | |
| Yellow (yellow) | |
| Key | |
| Green | |
| Violet | |
| White-Brown | |
| White-Orange | |
| White-Yellow (yellow) | |
| White-Green | |
| White-Violet |
Common GI Problem Causes (listed by probability/ease of testing and correction)
GI Bulbs Not Lighting
Let's start by determining if the problem is "off board", i.e. not on your power/driver board, or "on board".
- Take note of the wire color of the GI string that is not working.
- Set your DMM to AC voltage. If your DMM is not an "auto-ranging" model, expect to measure about 7 volts AC.
- Turn the game on.
- Insert one probe of your DMM (either one) into the rear of the female connector position with the same wire color as noted earlier. Make sure you make contact with the conductor.
- Insert the other probe into the rear of the female connector with the white wire that has the same color "tracer" as the color noted earlier.
- You should be measuring 6 to 7 VAC.
- If there is voltage at the connector, then the problem is "off board".
- If there is no voltage at the connector, then the problem is "on board".
Off board GI problems
- All lamps blown. Don't laugh. Just for giggles, put a known working lamp into one of the lamp sockets of the suspected GI string. I've seen it more than once. Usually the result of operators never changing a bulb, or somehow connecting higher voltage to the circuit.
- "Open" in GI wiring. The GI wires leading from J120/J121 may be cut/broken between the connector and the GI lamp sockets. Remove both of the female connectors at J120/J121. Use your DMM to check continuity between the lamp socket and the appropriate wire/pin at J120/J121.
On board GI problems
- Blown fuses. This is also the easiest problem to fix. Check each GI fuse following this procedure. Don't trust your eyes.
- Loss of "Cross Board" Connectivity. This problem is generally caused by burned header pins, traces, or in some cases, poor prior repairs. Use the following table to check cross board connectivity with J120/J121 as your target. Buzz between the pins/parts shown in the table or use the diagrams below.
GI Connector/pin Connects to ...and to fuse associated circuit wire color J120-1 Triac Q18 tab Brown J120-2 Triac Q10 tab Orange J120-3 Triac Q14 tab Yellow (yellow) J120-4 Key pin J120-5 Triac Q16 tab Green J120-6 Triac Q12 tab Violet J120-7 J115-3 F110 White-Brown J120-8 J115-4 F109 White-Orange J120-9 J115-6 F108 White-Yellow (yellow) J120-10 J115-5 F107 White-Green J120-11 J115-2 F106 White-Violet GI Connector/pin Connects to associated circuit wire color J115-7 Triac Q10 pin 1 Orange J115-8 Triac Q18 pin 1 Brown J115-9 Key pin J115-10 Triac Q16 pin 1 Green J115-11 Triac Q14 pin 1 White-Yellow (yellow) J115-12 Triac Q12 pin 1 Violet - WPC-089 Power/Driver Board GI Buzz Diagrams provided by Sascha Voskuil
Brown GI String 
Orange GI String 
Yellow GI String 
Green GI String 
Violet GI String
Click on the thumbnails above for the full sized GI buzz image
The clickable images above, in an animated gif... 
Regarding poor prior rework, sometimes when J120 is replaced, the through holes at pins 7 and/or 8, are pulled causing a loss of connectivity from the board front to the board rear. This will prevent the brown and/or orange color GI circuit from working properly. Additionally, the through hole at J121, pin 6, that routes power to the 3-pin connector at J119, if pulled, will cause the cabinet GI (violet) to not light (coin door lights).
- Burned connectors.
Over long periods of time, both the male and female GI connectors at J115, J120, and J121 often burn.
This was especially prevalent in early WPC games like Terminator 2.
Numerous "hacks" have been employed over the years by well meaning repairmen but the only real way to fix burned connectors is to replace both the male header pins and the female housings/pins. "Trifurcon" phosphor-bronze crimp-on pins are recommended to provide a better connection at the female connector. Note that these must be phosphor-bronze (7A rating, as original). Don't buy them unless the supplier calls that out as the brass version looks the same but is only rated at 5A. If you replace burned female connectors, the male connectors are probably burned too and should be replaced. The damaged surface of the male pins will generate heat, and cause early failure of the replacement connector. Plus, the GI will be dimmer than it should be. J115 is a special case. The black Panduit connector that Williams used on many machines is far superior to any crimp pin, with a 12A rating (compared to 7A for phosphor-bronze Trifurcon pins). These, however, can be hard to find. Fortunately, they rarely burn and therefore rarely require service. Another alternative for high current connections is to use Molex MarKK series contacts (Molex part number 45570-3050) along with Molex 41695 series plugs. Although they cost more than the Trifurcon style contacts, these contacts are rated for a current load up to 13 amps.
WPC-089 Power/Driver Board J120/J121 connector repair parts list...Qty Part Product ID 2 11 pin .156 male header (cut to size) 26-48-1245 2 Connector, .156 Plug, 11 pin (Molex 41695 series) 09-50-8111 10 .156 Trifurcon crimp contacts for the larger gauge wires 08-52-0113 10 .156 Trifurcon crimp contacts for the smaller gauge wires 08-52-0125 2 "Keying Pins" for Molex 41695 series plugs 15-04-0297 1 Crimp tool 1028-CT (or equivalent) Note: Product IDs shown above can be found at http://www.greatplainselectronics.com/Category-80.asp. Other vendors may carry these same parts.
- Burned AC power input connector. There is also a 9-pin (3x3) connector between the transformer secondary and J115. This connector/pins sometimes burn and may require replacement. Check to ensure that AC power is being delivered to the power/driver board at J115.
- Set your DMM to AC voltage. If your DMM is not an "auto-ranging" model, expect to measure about 7 volts AC.
- Turn the game on.
- Insert one probe of your DMM (either one) into the rear of the female connector at J115, pin 3.
- Insert the other probe into the rear of the female connector at J115, pin 11.
- You should be measuring 6 to 7 VAC.
- If no voltage is present, examine the 9-pin connector between the transformer secondary and J115, pictured at left.
- Burned traces. Usually, this is a secondary problem created after the connectors burn. Visual inspection of the traces might uncover the problem, but "buzzing" them for continuity is the best practice.
- Failed 2N5401. These don't fail very often, but are easy to test following this procedure.
- Failed resistors. Again, these don't fail very often but are easy to test with your DMM. Keep in mind that "in-circuit" measurements may not be reliable.
- Failed 74LS374. This is rare too but easy to test following this procedure. You can also test the outputs of the LS374 by probing pins 2, 5, 6, 16 and 19 with your logic probe. At full GI brightness (8), these pins should test as solid "low". At the dimmest GI brightness (1), the above referenced pins should all be pulsing "high". Additionally, pin 1 of the LS374 should always test low and pin 11 should always be pulsing "high".
- Failed Triac. These rarely fail. But, if you've gotten to this step in the procedure, it's time to replace the Triac. Remember, you need a 4-sector triac.
As these boards age it is easy to pull out the little copper hole liners that connect traces from one side of the board to the other. If you install new connector pins, be sure to check continuity from the new pins onto the board somewhere. This only takes a couple minutes and can save you a lot of time.
6.28.2.1 GI Lamps Not Dimming
The primary cause of GI lamps failing to dim is broken traces at BR2, usually caused when BR2 was replaced. These traces lead to D3 and D38. Both of these traces must be intact for dimming to work as they supply the power to generate the signal to the Zero Cross circuit (ZC) which is key to dimming.
Before you go too far diagnosing the hardware, if your WPC game will not dim the general illumination, make sure that Standard Adjustment #25, "Allow Dim Illum.", is set to "YES". If set to "NO", then the GI will never dim, even during General Illumination test.
General dimming "theory of operation"...
- The driver board generates the ZC signal with the BR2, D3/D38 and U6 circuitry (different resistors).
- The ZC signal is connected to the ASIC (across the driver board, the ribbon, and then across the MPU).
- The ASIC uses the ZC signal to determine when to send the /TRIAC signal to U1 pin 11 (an 74LS374 buffer IC) as it simultaneously presents GI string enable data on the data bus.
- U1 latches GI string enable data from the MPU's data bus.
- The output of U1 forms signals T0 thru T4, which enable the TRIAC circuitry.
It is possible that D3, D38 (1N4004 diodes) or the LM339 at U6 have failed. If the ZC test point on the power/driver board is not strobing (which can be seen with a logic probe), something upstream of the test point has failed.
U6 is an LM339 comparator. The resistors around it (R16 and R17, both 230 ohm 1/4 watt) help generate the correct ZC signal. If a resistor is burned or out of spec, or if a trace is broken in the circuit (there are several "vias"), then ZC may still strobe but in an incorrect way which the ASIC doesn't recognize as the zero cross signal.
The ZC may be strobing, yet the GI still won't dim. Use a logic probe to test both sides of diodes D3 and D38 as it is necessary for both the positive going and the negative going portions of the AC sine wave to be detected. If the traces buzz out back to BR2, then suspect one side of BR2 being open. Incredibly, it is possible for the game to work correctly in all regards other than GI dimming with half of the bridge open. Odd...but it happens.
6.28.3 WPC-95 General Illumination Problems
The General Illumination circuit for WPC-95 games is very similar to WPC games. When the WPC-95 system was implemented, Williams reduced the number of "dimmable" GI circuits from 5 to 3, with 2 of the circuits being lit at all times. Within the two "always on" GI circuits, Williams placed 8 large 6A2 diodes, to create a voltage drop in the circuit which would dim the lamps slightly and presumably lengthen lamp life. However, these big 6A2 diodes create a great deal of heat. Without a heat-sink like those used on the TRIACs, the high heat they produce causes the printed circuit board and traces to burn.
Later versions of the WPC-95 driver board replaced these 6A2 diodes with zero ohm jumpers.
You can (and probably should) remove the 6A2 diodes, and either replace them with zero ohm jumpers as pictured at right, or add jumpers to the solder side of the board as pictured at left. The solution at left bypasses the diodes completely, by installing the following jumpers.
■ J103 pin 11 jumped to J105 pin 5
■ J103 pin 12 jumped to J105 pin 6
- WPC-95 Power/Driver Board GI Buzz Diagrams provided by Sascha Voskuil
Brown GI String 
Orange GI String 
Yellow GI String 
Green GI String 
Violet GI String
6.28.4 Controlled Lamp Problems
6.28.4.1 Twist Socket Lamp Not Lighting
Two things that can fail on lamp boards are individual lamp circuit diodes or the solder pads can develop "divots", where the twist sockets make physical contact with the board. To overcome the divots, simply add a little solder, and carefully reflow the solder pads. Make certain not to apply too much heat...just enough to evenly flow the solder.
With Fire!, a system 11 game, Williams started using lamp boards with .156" header connections for the lamp column and row lines. This allowed for easy removal and service of the lamp boards. However, it introduced some new problems. Because the lamp boards used were single-sided, (this was presumably a cost analysis decision), the .156" header pins can develop cold solder joints and crack due to vibration. The problem can easily be rectified by removing the old solder from the header pins and applying fresh, new solder.
- Typical issues with lamp board sockets and headers
"Divots" in the connection pad of a "twist in" lamp. 
The solder on these header pins has been reflowed nicely.
The following actions can help debug an individual socket failure:
- Move the non-working twist socket to another spot that is working. This will test that the bulb and socket itself are working. If not, replace the bulb, try to adjust the socket's contact legs, try to clean off the contact points if they are dirty, and if all that fails, replace the twist socket.
- Move a working twist socket into the position that is not working. If the socket works, the original socket may have been the problem. If the working socket also does not work in the non-working position, there is likely a problem with that position.
- Check the connector, especially if it is an IDC connector. Sometimes a wire can pop out and lose connectivity.
- Remove the lamp board. Check the header pins for cracked solder joints and reflow the solder as necessary. Reinstall and test.
- Test the diodes with a multimeter. If any are bad, replace them. Make sure to orient the diode the same way that is indicated on the silkscreen. It's sometimes possible that a previous owner installed a diode the wrong way.
- Sometimes the pads on the lamp board that the socket makes contact with get dirty or worn enough to put a divot in the metal. Clean off the contacts, and if that doesn't improve anything, tin the pads with a thin layer of solder.
- If none of this was successful, test for continuity between the lamp board and the driver board.
- If wiring continuity checks out, troubleshoot the issue like any other controlled lamp.
6.28.4.2 Controlled Lamp Operational Description
WPC feature lamps are controlled from the WPC MPU and ultimately enabled via the driver board. The control signals are as follows.
- The 68B09EP places a data bit pattern on the data bus. This represents the lamp column to be strobed.
- The bit pattern is conveyed to the driver board via the ribbon cable between J211 on the MPU and J113 on the driver board.
- U9 on the driver board (a 74LS240) buffers the column bit pattern for U18 (a 74LS374).
- The ASIC on the MPU asserts the /LMP COL signal which "clocks" the data into U18 by pulsing pin 11.
- U18 outputs are connected to the ULN2803 at U20, which inverts the signal and enables one of eight TIP-107 Darlington transistors (Q91 thru Q98) that enable 18VDC to flow to the enabled column. This completes the column "strobe" portion of lamp matrix operation.
- The 68B09EP places a data bit pattern on the data bus. This represents the lamp rows to be strobed.
- The bit pattern is conveyed to the driver board via the ribbon cable between J211 on the MPU and J113 on the driver board.
- This bit pattern data is presented to four 74LS74s (Dual D-Type Flip-Flops) at U10 thru U13. This sets up a path to ground for the 18V lamp matrix power for each row enabled by the bit pattern
- The ASIC on the MPU asserts the /LMP ROW signal which "clocks" the data into U10 thru U13 via their "reset" signal inputs.
- The (not) Q signal of each 74LS74 enables one of eight TIP-102 Darlington transistors (Q83 thru Q90) that provide the actual path to ground (through a .22 ohm 1 watt resistor) for the 18V lamp matrix power.
- At this point, power flows from the enabled column circuitry, through the game wiring to the lamps, then through the row circuitry to ground for the rows that are enabled.
- The row enable signal is switched off when the LM339 comparators at U15 and U16 detect a voltage rise above the reference voltage present at pins 5, 7, 9, and 11 of both LM339s, via the "set" signal of each 74LS74 (U10 thru U13).
This process repeats itself over and over with the MPU cycling through columns 1 thru 8 while enabling specific rows, lighting lamps at the intersection of the enabled column and the enabled rows.
There are many possible causes for lamp matrix malfunctions. Some reasons, in order of probability are:
- Lack of 18V lamp matrix power. If LED6 is not lit, or TP8 shows other than 18V, "buzz" F114 for continuity with your DMM. If F114 is blown, test BR1 using the method specified here.
- Failure of the row (TIP-102) or column (TIP-107) drive transistor. Both of these are easily diode tested and compared to the other 7 row/column drive transistors.
- For a column failure: Failure of the ULN-2803 at U19. U19 works the same as U20 in the switch matrix, providing a periodic pulse to all columns.
- For a row failure: Failure of a 74LS74 at U10/11/12/13. Again, these parts can either be diode tested for, better yet, use a logic probe to see if they are delivering the necessary pulses. Compare the operation of similar pins.
- Failure of the associated .22 ohm 1 watt resistor in the path between 18VDC lamp matrix power and ground (R150 for example).
- Poor connections between J211 on the MPU and J113 on the power/driver board. Sometimes, reseating the ribbon cable on both ends will "fix" the issue. Replace the ribbon cable and examine the dual row headers if the problem becomes chronic.
- Prior work on the power/driver board. The data bus runs completely across the power/driver board, stopping in at several 74LS374s (U1 thru U5) along the way. The signals pass through the board from component side to solder side at U9. If the same column and row of the lamp matrix are not lighting (i.e. column 5, row 5), it's a good bet that the signal for that row/column is compromised in the area of U9. The traces at each IC are delicate and it's tough for most hobbyists to remove a 20 pin IC without damaging the traces. It's particularly vexing to encounter a problem where a data signal is held low or high by one of the 74LS374s since each data signal is connected to all of them and even using [diode test] sometimes can't identify the faulty IC. Some techs will cut the data signal pin close to the PCB for a 74LS374, using the process of elimination to identify the culprit (not recommended). Enough said, but it's easily seen that power/driver boards can be damaged quite easily by the novice. Send it to a pro.
- Fatigued connections between the ASIC on the MPU and it's chip socket. Since the ASIC provides critical enable signals for the lamp matrix, reseating or retensioning these pins is reasonable course of action. Use a PLCC removal tool to safely remove the ASIC without damaging the socket.
- Failure of any of the ICs noted above. Each of these ICs can be tested with a DMM set to diode test
- Corrosion on the MPU that might have compromised the enable signals, as seen in the picture at right. Corrosion can and will attack under the header pins at J211 on the MPU.
Quick Test of Lamp Column Transistors
If the game has an entire column of lamps locked on, there is a good chance that a lamp column transistor has shorted. Testing for this condition is very simple. Set your DMM to continuity. Touch one probe to the 18V lamp matrix test point as pictured at left. Touch the other probe to the tab of each of the TIP-107 transistors. Any that "buzz" are shorted and will need to be replaced.
General Lamp Matrix Testing
The control logic for the WPC lamp matrix can be tested by connecting a spare lamp using two jumper wires. The following sections show the separate procedures for testing the lamp matrix columns and rows. The example applies to WPC-089 power/drive boards. The procedure is the same for WPC-95 power/driver boards, but the connector designations and transistor numbers differ. Images authored by Sascha Voskuil, used with permission)
Column 4 shorted in the lamp matrix circuit on a WPC-95 Power/Driver board
Column 4 inoperative in the lamp matrix circuit on a WPC-95 Power/Driver board
Note: In this animation, columns 4 and 2 are inoperative.
We provide this section for completeness knowing that WPC games offer independent lamp row and column tests as part of the diagnostics.
Testing the lamp matrix columns:
Use the following procedure to test the TIP-107 transistors that drive the lamp matrix columns. Note that a diode is not needed for these tests since it's function is to block current flow and prevent interaction between the lamps in the matrix. In this test we are connecting a single lamp at a time.
- Remove the backglass and open the insert to get access to power/drive board connectors J133/134/135 (row) and J136/137/138 (column).
- Unplug all connectors with red or yellow wires leading to them. These are the lamp matrix connections (lower right corner of power/driver board)
- Turn the game on and start "All Lamps" test in the Test/Diagnostic Menu.
- Clip one end of the test jumper to J137 pin 1, the rightmost pin on the connector
- Touch the other end of the jumper to J133 pin 1, the rightmost pin on the connector
- The test lamp should flash to indicate that the column driver is working.
- Repeat the test for the pins 2 through 9 on J137. There is no pin 8 as it is the key.
If a column doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.
The following table shows the lamp number and driving transistor for each of the column pins.
| Pin | Wire Colors | Lamp number | Transistor number |
|---|---|---|---|
Testing the lamp matrix rows:
Use the following procedure to test the TIP-102 transistors that drive the lamp matrix rows.
- Remove the backglass and open the insert to get access to power/drive board connectors J133/134/135 (row) and J136/137/138 (column).
- Unplug all connectors with red or yellow wires leading to them. These are the lamp matrix connections (lower right corner of power/driver board)
- Turn the game on and start "All Lamps" test in the Test/Diagnostic Menu.
- Clip one end of the test jumper to J133 pin 1, the rightmost pin on the connector
- Touch the other end of the jumper to J137 pin 1, the rightmost pin on the connector
- The test lamp should flash to indicate that the column driver is working.
- Repeat the test for the pins 2 through 9 on J133. There is no pin 3 as it is the key.
If a row doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test. The following table shows the lamp number and driving transistor for each of the row pins.
| Pin | Wire Colors | Lamp number | Transistor number |
|---|---|---|---|
6.28.4.3 Lamp Issue Caused by Connecting "Growth" Connectors
An issue that seems to come up fairly often is caused by literally placing a square peg into a round hole.
The images shown here from a Judge Dredd shows a "growth" connector wired from the factory that was never used during production. It happens to be in the proximity of J136, a lamp matrix connector and the wires are lamp matrix wires (colored red and colored yellow). One could almost be forgiven for forcing the female housing onto J136 even though the connector types are different.
With this connector in place, all kinds of lamp matrix havoc ensues as shown in one lamp matrix "error map" shown at left.
The solution is simple. Remove the connector.
All images provided by Chuck Sanderson, CP Pinball
6.29 Switch Problems
Switches in WPC games fall into two categories, those within the switch matrix, and "direct" switches.
6.29.1 Diode and Switch Matrix Wiring Orientation on a Microswitch
First and foremost, all switches located in the switch matrix MUST have a diode. Secondly, the diode has to be installed in the correct orientation. If a diode is installed "backwards", the end result my be that all of the switches in that particular row get triggered or even stranger issues occur. Finally, the diode legs must not be connected to any of the other wires or terminals of the switch, or the switch will funk up the switch matrix.
Here is the correct orientation for the wiring and the diode on a microswitch. The white wire w/ trace and non-banded side of diode is connected to NC terminal. The banded side of diode is connected to common terminal. Finally, the green wire w/ trace is connected to NO terminal.
6.29.2 Built-in Switch Testing
WPC games monitor switch closures as the game is played. If a switch is not activated after a certain number of balls (usually 30, but will vary depending on the switch in question), the game will show the "credit dot", an indication to the operator that a switch may be faulty. Some switches are not often closed (like switch 55 located in the White Water pop bumper garden) and some switches simply aren't hit by rookie players (like the upper exit to the Twilight Zone mini playfield). Some switches will be marked non-operational immediately after a certain event where the switch is known to have been activated (switches related to The Shadow's brick wall drop target are one example; any error in the lock sequence causes the credit dot to light immediately).
There is a table held in RAM that contains counters for all monitored switches. Each ball served decrements the counter for each switch; as soon as that switch is hit on the playfield, the counter is reset to the initial value. The credit dot gets lit when any counter for any monitored switch goes to zero. Switches such as flipper optos are set to very low initial values, as flippers are hit on every ball. It would have been possible to have higher values set for switches that would occasionally be activated but not often by novice players as noted above, however this aspect of the programming was rarely if ever used.
When a credit dot is lit, often the game will offer "switch compensation", which was a Williams' patented feature, that allowed a nearby or alternate switch to achieve the same result as hitting the original, marked non-operational, switch. This enabled a game with faulty switches to still be played close to the original gameplay. Sometimes the faulty switch will auto-clear itself when activated, but more often than not, the fault would have to be cleared manually. To clear a switch manually, enter the "Switch Edges" test (as described below), and manually activate the switch. If the switch in question is functioning properly, activating the switch will remove the credit dot.
The first action to be taken is to enter diagnostics. The game will indicate the reason(s) for the credit dot on the display, upon pressing the enter button on the coin door to receive a test report.
Since the normal switch matrix is 8 by 8, games like Twilight Zone, Star Trek: The Next Generation, and Indiana Jones employ a 9th column of switches. These switches are tested via a dedicated switch test tied to the playfield feature. An example is the Star Trek: The Next Generation cannon switches.
6.29.2.1 T.1 Switch Edges Test
Switches can be tested by entering Test T.1, Switch Edges. Switch Edges Test presents an 8 by 8 switch matrix grid with one or two switch columns outside of the matrix. The additionally columns are for dedicated switches. The left column is for switches located on the coin door (all WPC games), and the right column is for flipper cabinet and flipper EOS switches (WPC games which use a Fliptronics board - Addams Family and newer). Open switches show as a simple dot on the DMD. Closed switches show as a boxed dot on the DMD. Microswitches and leaf switches will show as a dot when open. Optos will show as a boxed dot when the opto beam is not being broken. The last closed switch name and number will be shown on the display along with the two wire colors that are connected to that particular switch. While in switch edges test, manually closing properly operating switches will be shown on the display.
6.29.2.2 T.2 Switch Levels Test
6.29.3 Direct Switch Problems
Direct switch operation
Direct switches include:
- Left coin chute
- Center coin chute
- Right coin chute
- 4th coin chute
- Service Credits/Escape (referred to as "escape" here)
- Volume down/Down
- Volume up/Up
- Begin Test/Enter
Direct switches are not part of the WPC switch matrix. All of the direct switches are located on the coin door, and connect to the MPU at J205. The MPU senses these switches individually, and apart from the switch matrix. Therefore, isolation diodes are not used with direct switches.
Normally, with the switch open, the LM339s at U16 and U17 compare 12V (supplied on the MPU to both the switch and to the LM339) with 5V (as a comparison level) and signals the 74LS240 at U15 that the switch is open. When the switch closes, it shorts the 12V to ground and the comparison at the LM339 then indicates to U15 that the switch is closed. U15 is "clocked" by pin 48 of the ASIC (SW DIR), causing U15 to present its data to the data bus. The 6809/ASIC "debounces" the switch. Debouncing is not a factor to be considered here and doesn't factor in switch testing at all.
Direct Switch Pinout at J205 for both WPC and WPC-S MPUs
Notes:
- J205, pin 5 is the "key" pin.
- J205, pin 10 provides ground (black wire)
- J205, pin 11 is unused
- J205, pin 12 is an "enable" back to the coin door interface board
| Signal | Wire color at J205 | MPU pin | Diode | LM339 & input pin | U15 input pin |
|---|---|---|---|---|---|
| Left chute | |||||
| Center chute | |||||
| Right chute | |||||
| 4th chute | |||||
| Escape | |||||
| Down | |||||
| Up | |||||
| Enter |
Debugging direct switch problems
To discover the problem as quickly as possible, we'll divide the problem into smaller pieces. We must first determine if the problem is on the MPU board or the problem lies with the wiring to the coin door and/or the specific switch. If your MPU has obvious alkaline damage at U15, U16, or U17, address the alkaline damage first.
Begin testing with the game OFF.
Isolate the problem to the MPU or to the game wiring/switch
- Remove connector J205 from the MPU.
- Build a jumper wire with alligator clips on both ends.
- Clip one end of the jumper wire to the game's ground braid in the game head.
- Turn the game on
- Carefully touch the other end of your jumper wire to the appropriate pin on J205 as shown in the table.
- If the MPU carries out the function of the switch, the problem is not on the MPU.
- If the MPU does nothing, the problem is on the MPU.
- Skip to the appropriate section below.
Identifying problems NOT on the MPU
Test the direct switch's path to ground
- Your game should still be turned off.
- DMM set to continuity.
- Clip the black lead of your DMM to any game ground, like the lockdown bar or ground braid.
- Red lead on the solder joint between the switch and the black wire that provides ground.
- You should hear "tone". If not, further diagnose the break in the black wire between the solder joint and game ground.
Test the direct switch itself
- Black lead of your DMM still clipped to game ground.
- Red lead on the solder joint opposite the black wire (or bare wire jumper) of the switch under test.
- Depress the switch. You should hear "tone". If not, the switch is defective and not "making". See the section below that describes cleaning these switches.
Test the signal path to the MPU
- Clip the black lead of your DMM on the solder joint opposite the black wire (or bare wire jumper) for the switch under test.
- Remove the connector plug at J205 from the MPU.
- Red lead on the appropriate pin of J205 for the switch under test. See the table above. It's easiest to access the pin through the rectangular hole in the back of the connector where the pin's "tang" snaps in.
- You should hear "tone". If not, there is a discontinuity in the wire between the direct switch and J205. Note that the coin door interface board is between these two points. The coin door interface board is a "pass-through" for these signals and rarely causes a problem. Still, reseating connectors J1, J3, and J4 on the coin door interface board might uncover the problem. More likely, the wire between J1 on the coin door interface board and J205 has a break in it.
Identifying problems on the MPU
Test the signal path through J205 and onto the MPU
J205 is right below the battery holder and as such, sometimes receives the unwanted gift of dripping alkaline from depleted batteries. Carefully examine both the male and female connections of J205 for alkaline "greenies". Assuming no alkaline damage...
- Begin with your game turned off.
- Connect J205 to the MPU.
- Clip the black lead of your DMM to the solder joint opposite the black wire (or bare wire jumper) for the switch under test.
- Red lead on the banded end of the appropriate diode shown in the table above.
- You should hear "tone". If not, there is either a problem with the physical connection at J205 or the alkaline "greenies" are sneakier than you gave them credit for. Re-examine J205 and the surrounding area of the board for alkaline damage. The traces from the switch connectors are very small and it takes very little alkaline damage to compromise them. You may also re-pin the female side of J205.
At this point, a logic probe would be the best tool to use. You can pick up 5V power for your probe across the electrolytic cap at C31 which is immediately to the right of the battery holder. Black lead on the negative side (top of the cap). Red lead on positive side (bottom). The board is silkscreened with polarity markings. Set the logic probe to "CMOS" test mode, as you will be measuring 12VDC.
If you don't already have a logic probe, you should. Although for this test, you can still get by with your trusty DMM. Clip the black lead of your DMM to game ground. The ground braid in the head is a good place to pickup ground at this point. Set your DMM to DC volts.
Test the LM339 inputs
- Start with the game turned off.
- Again, set your logic probe to "CMOS"
- Clip one end of your jumper wire to the appropriate pin of J205. Leave the other end of your jumper wire unconnected, but handy as you'll touch it to ground later.
- You now need to turn the game ON.
- Measure the signal at the appropriate LM339's appropriate pin shown in the table above. Either place your logic probe on the pin or place the Red lead of your DMM on the pin. The signal should measure high (or about 12VDC with your DMM).
- Now, with your other hand, touch the free end of your jumper wire to the ground braid in the backbox as you observe the results.
- You should see the signal transition to low. If you still measure high, then the pin isn't being grounded correctly. Candidates are a failed diode/resistor in the circuit, the board trace between the diode and the LM339 is compromised, or a badly failed LM339.
Test the LM339 outputs/74LS240 (U15) inputs
- Set your logic probe back to TTL as you will be measuring 0 - 5V signals
- Measure the signal at the appropriate pin (see table) of U15. The signal should measure high (or about 5VDC with your DMM).
- Touch the free end of your jumper wire to the ground braid in the backbox as you observe the results.
- You should see the signal transition to low. If you still measure high with the jumper wire grounded, then either the LM339 outputs have failed, the board trace between the LM339 and U15 is compromised, or the 74LS240 has failed and is corrupting the signal. You can test U15 using the procedure in the "How to..." section of PinWiki, here.
The output side of U15 can't be tested effectively since that is the processor/ASIC data bus and should be constantly and irregularly changing states.
If you've followed this process step-by-step, you should have identified the problem with the signal and will be able to effectively perform the appropriate repair.
Cleaning direct switches
Coming soon...will describe disassembly and cleaning... Sometimes, several rigorous open/close cycles will "clean" corrosion from the switch.
6.29.4 Switch Matrix Problems
Isolate the problem to the MPU or to the game wiring/diodes/switches
Follow these steps to determine if the switch matrix problem is on the CPU or somewhere in the game wiring.
- Remove connectors J206/J207, J208/209 and J212 from the bottom of the CPU (J206 and J207 are electronically the same and J208 and J209 are electronically the same).
- Clip one lead of a test jumper to pin one of J207 making sure you don't touch any of the nearby pins on J207.
- Power the game on, and enter Switch Edge test (you've left J205 on the CPU so the diagnostics switches still work).
- Touch the other end of the jumper to pin one on J209, then pin two and so on. You should see (and hear) the CPU indicate that switches #11, #12, #13, etc. are being "made" as you touch the pins of J209. You should *never* see multiple switches being made.
- Move the jumper from J207 pin 1 to pin 2. Re-test to every pin on J209, listening for the machine to read every switch as closed. Continue in a similar manner testing each pin of J207 to every pin in J209.
The following images, provided by Sascha Voksuil, grapically depict the above tests of the on-board switch matrix circuitry with a jumper wire. A diode is not required since the test jumpers directly from a single pin to a single pin. Remember, the purpose of switch diodes is switch isolation. Also, have no fear conducting this test. Unless you connect one end of the wire to high voltage, nothing can be damaged.
If only one switch shows on the Switch Edge test for each pin combination, then the CPU's switch matrix is working properly and you can confidently assume that any switch problems lie elsewhere. Possibilities include a shorted wire, bad/broken/shorted diode, bad under playfield opto board, bad coin door interface board, etc. If the problem is observed with row 2 of the switch matrix, and you're game has a "-1 Power/Driver" board installed (the one with the flipper power relay), it is possible that one/both of the 4N25 opto-isolators on the power/driver board have failed. These opto-isolators communicate flipper switch closures for pre-FlipTronics games.
If multiple switch closures are reported when you touch one pin of the connector, or if the CPU reports a row or column short, then there is a fault with the switch matrix circuitry on the CPU board itself. Be aware that an additional fault may still be present on the playfield. Switch matrix chips do not simply blow for no reason!
- Blown ULN2803 (U20) Examples
An obviously blown ULN2803 (U20) caused by shorting 50V coil power to the switch matrix. Ouch! 
Another obviously blown ULN2803...happens all the time...Don't work on your game with power on. 
Another obviously blown ULN2803...the HV jolt also took out U14, a 74LS374 which buffers the ULN2803 from the processor data bus.
Catastrophic Failure of ULN2803 or Other Switch Matrix Parts
One fairly common reason that a ULN2803 or other switch matrix circuitry may blow is a short to coil power. In the picture at left, the coil that actuates the "Bridge Diverter" on the game Twilight Zone, is touching the coil bracket on one side. Since coil power is present at both coil lugs (which is normal), a coil lug touching metal will conduct coil power to that metal. In this case, the coil bracket touches the bridge diverter piano wire and then the coil diverter and then the entire wireform. If a switch matrix solder tab or switch blade metal shorts to the wireform, poof! Get ready to replace the ULN2803.
Another way for HV to destroy the ULN2803 and other switch matrix circuitry is shown at left. Here, the coil wrapper has worn through, and then the enamel coating on the coil winding rubbed away, causing a short of coil power to the coil bracket. Just as the instance above showed, this places coil power onto the coil bracket and anything touching it, including switches.
6.29.4.1 MPU Circuitry Switch Matrix Problem Diagnosis
6.29.4.1.1 Quick Switch Column Strobe Testing
A quick way to test that switch column strobes are working properly, is to use a logic probe as shown in the picture at left. Each pin of J206/J207 (all WPC MPU versions) should be pulsing high.
6.29.4.1.2 Further MPU Circuitry Diagnosis
The following image (authored by Sascha Voskuil, used with permission) will help diagnose particular ICs at fault on the MPU.
Let's use the diagram above to walk through a simple "on board" switch matrix issue.
A board presented with very slight alkaline damage to U20, the ULN2803. After socketing, and replacing the ULN2803, column 3 still failed to strobe. We used out logic probe to determine that pin 16 of U20 was strobing. Therefore, there MUST have been an on board fracture of the trace. Setting our DMM to continuity, and buzzing between J206 pin 3 (marked with a gray "3" in the diagram) and U20 pin 16 failed. Moving our probe from J206 pin 3 to the junction of R69 and C13 (also marked with a gray "3" in the diagram) succeeded. However, buzzing between the junction of R69/C13 and U20 pin 16 succeeded. Using this information, we must conclude that the discontinuity in the trace was between J206 pin 3 and the junction of R69/C13.
The picture at left shows the problem. Once the J206 header was removed, we could see that alkaline had dripped onto the connector and leached down to the solder joint. The corrosion etched enough of the trace away to prevent connectivity.
The picture at left shows another WPC-089 MPU board with a similar problem, but much worse. This board was the victim of dripping alkaline which invaded the trace which runs under the "C17" label to J206-9 and J207-9.
The picture at right shows the female connector housings that were the victim, and transportation medium, for the alkaline corrosion. The connector on the left required repinning. The connector on the right showed only light damage which was cleaned up with a vinegar swab.
Another clear example of a connector requiring replacement is shown at left.
6.29.4.2 Switch 11 or Switch 12 Reported as Closed With All Switch Matrix Connectors Removed
A seemingly impossible behavior can be caused by a failed 4N25 Opto Isolator on a "-1" version of the WPC Power/Driver board including RottenDog Power/Driver boards. After removing all switch matrix connectors (not the direct switch connector) from the MPU, switch 11 and/or switch 12 will be reported as closed. This can also lead to all of column 1 being reported closed when any switch is closed outside of column 1. All of the column that switch is in will also be reported as closed.
The 4N25s can be tested as described below.
Another quick test is to remove the ribbon between the MPU and the Driver board. This prevents the driver board from reporting closed switches.
6.29.4.3 Cabinet Flipper Switch Detection Problem Diagnosis for Pre-FlipTronics Games
Pre-FlipTronics games detect closure of the flipper cabinet switches via two 4N25 Opto Isolators on the "-1" version of the power/driver board. If the "cursor" can't be moved during entry of HSTD initials or if the cabinet flipper buttons don't control video mode correctly, there is a good chance that one/both of the 4N25 opto isolators is shot. Games that shipped with the "-1" Power/Driver board include:
- Funhouse
- Harley-Davidson
- The Machine: Bride of Pin*Bot
- Gilligan's Island
- Slugfest
- Terminator 2: Judgement Day
- Hurricane
- Party Zone
The image at left illustrates the switch matrix connection between the 4N25 Opto Isolators on the Power/Driver board and the MPU board.
Note that some revisions of the WPC schematics contain an error, as illustrated by the image at left.
Fortunately, testing an opto coupler is simple using the diode test function provided by most DMMs. Set the DMM to diode test, compare results against those pictured below (this test conducted on a 4N25 contained on a System 11 Interconnect Board).
- Testing a 4N25 Opto Coupler
The internal schematic of the 4N25. Pins 1 and 2 connect to an internal diode (LED). Pins 4 thru 6 connect to a PNP photo transistor. 
Testing the diode connected to pins 1 and 2. Red on pin 1, black on pin 2 
Testing part of the photo transistor. Black on pin 5, red on pin 6 
Testing part of the photo transistor. Black on pin 4, red on pin 6
6.29.4.3.1 Special Note regarding RottenDog Power/Driver boards manufactured prior to February, 2012
RottenDog aftermarket power/driver boards manufactured prior to February, 2012 contain a trace layout/connection error that exchanges the function of the two 4N25 Opto Isolators on the board. That is, the 4N25 that should report a left flipper closure actually reports a right flipper closure, and vice-versa. This error can be corrected via two cuts and two jumpers, as illustrated in the image at left.
Shown at left is the correction implemented by PinSider "troxel".
The same image, annotated by Pinsider "zaza", calls out the need for caution when making this mod. As can be seen, 75VDC is present in the area. A better implementation might be to route the jumper wires around the 4N25 instead of under it.
6.29.5 WPC95 Flipper Cabinet Switch Processing
The WPC-95 system implementation moved the cabinet flipper button and EOS switch sensing from the FlipTronics II board to the MPU board. Simple voltage level comparison via LM339s senses shorts to ground for those switches. The connector that cabinet switch wiring is connected to (J212) is directly below the battery holder where leaky batteries can "drip" onto the connector, corroding both under the connector and the pins on the connector. Corrosion can cause many odd problems. If this happens, the corrosion can cause the flipper buttons to be sensed intermittently and/or incorrectly.
Pictured at left is one case of corrosion impacting flipper operation. The corrosion caused the circuit to sense that both of the cabinet flipper buttons had been pressed when only one had been pressed. Standard alkaline corrosion cleanup takes care of this issue.
6.29.6 Opto Switches
6.29.6.1 Basic Operation
Williams opto switches are comprised of a "transmitter" and a "receiver" opto, which are each unique parts. This is different from later Sega and some Stern game systems where the optos that serve as transmitter and receiver are identical.
The transmitter opto is housed in a white plastic frame. It is powered by unregulated 12VDC. If the opto is good, measuring either solder joint of the opto should read about 12VDC as long as the game is turned on.
Note that the ball trough uses these opto transmitters also. Orient the ball trough transmitter flat side as is silkscreened on the board.
The receiver opto is housed in a black plastic frame. This "IR detector" opto conducts the 12VDC supplied to it, as long as the transmitter's "light" is cast upon it. Once the transmitter light is removed, the opto no longer conducts the 12VDC. Typically, circuitry on an "opto switch board" interprets the lack of 12VDC using an LM339 comparator, and indicates that the switch is open. Remember that the "sense" of opto switches is reversed from regular "hard" switches such as leaf switches and micro-switches.
Note that the ball trough uses these opto receivers also. Orient the ball trough receivers flat side so that the leg on the flat side is furthest away from the "ear" that is silkscreened on the board.
6.29.6.2 Opto Testing
The "sending side" or transmitter side of an opto pair, which should be housed in a white plastic frame, can be tested with just about any digital camera. In the picture at left, an iPhone camera was used to clearly see the purplish glow of a working opto sender.
The "receiving side" of an opto pair, which should be housed in a black plastic frame, can be tested with just about any strong incandescent flashlight. Note that an LED flashlight does not typically work too well for this test. Place the game in switch test. Block the sending opto that would normally illuminate the receiver under test. Shine your bright incandescent flashlight on the receiver opto. The switch state as shown on the display should change.
6.29.6.3 7 Opto Board Testing
The 7-Opto Board (A-14977, A-15576, A-15595) pictured at right, can be tested "in-situ" with a simple jumper wire and a DMM.
Procedure
Test the LM339 comparators
- Place the game into switch test (T.1)
- Remove the balls from the game to prevent them from crashing down on the playfield (or stuff a rag into the ball loading hole)
- Place the playfield in the vertical position
- Remove the J2 connector on the 7 opto board
- Clip one end of a jumper to J2/pin 10
- In turn, touch the other end of the jumper to pins 1 through 7 of J2
- With each connection, a opto switch activation should be enunciated on the display
- If all 7 switch activations are enunciated, this proves that all of the LM339 comparator circuits are working.
Test the 12VDC power supply circuits
- Set a DMM to DC volts (less than 20 if not using an auto-ranging DMM)
- Remove the J1 connector
- Clip the black lead of a DMM to J1/pin 10 (ground)
- With the DMM red lead, measure DC voltage at pins 1 through 8 (excluding pin 4)
- Each pin should measure about 12VDC
- If all 7 pins measure about 12VDC, this proves that each of the 12V power circuits (and the 270 ohm current limiting resistors) are working.
If a game opto pair fails to function properly, yet both of the above tests pass, then either the opto transmitter or receiver has failed or the wire/connector connection between the opto board and one/both playfield optos has failed.
6.29.7 "Jittery" Opto Switches
It is possible for all opto switches in the game to act erratically. This can be difficult to diagnose because the problem can manifest itself in various ways during game play. For instance, the bulldozer blade in "Roadshow" may occasionally be unable to find it's home position. Or, the auto launcher in "Twilight Zone" may seem to want to launch a ball when none is present. Since the cabinet flipper switches are sometimes optos as well, the game's flippers may also behave strangely.
The first step is to check the optos in switch edge test. If the optos appear to blink on and then off, when the actual physical state of the opto is open, suspect an issue with the unregulated 12VDC voltage.
Measure for about 12VDC at TP1 on the power/driver board. If the voltage is significantly below 12VDC (i.e. around 10VDC) then there may be a problem with the bridge rectifier at BR5 or the 15,000uf filter capacitor at C30. Examine the solder joints at C30, especially if that capacitor has been replaced in the past. A damaged through hole may effectively remove the filter cap from the circuit, AC voltage will remain in the power circuit, and the optos will be flakey.
Use your DMM to test the bridge rectifier and to "buzz" between the solder joints at the cap and the appropriate legs of BR5. If this connection is flakey, repair it using a solder stitch or connect jumpers from the C30 to BR5.
6.29.8 Other Switch "Jitter" Reasons
The electrolytic cap C2 in the regulated 12VDC circuit leaks quite often, eroding the traces, sometimes severing the connection completely and sometimes reducing the 12VDC power output to something lower. This can wreak havoc on the switch matrix as the regulated 12VDC is used by the LM339 comparators on the MPU board to detect switch closures. Normal cleanup procedures can be used; wipe clean, sand as necessary, retin traces, and replace the cap with a 100uf/35VDC cap (an upgrade).
6.29.9 Sub-microswitch Issues
Some WPC games have an issue with micro-switches that are heat damaged during game assembly. When soldering the wire lead(s) onto the switch, flux leaches into the switch body and, over time, causes the switches to become "sticky".
Game switches from smoky environments often become intermittent or fail. You may be able to repeatedly actuate the switch with your finger and get it to work for a game session, but when you return to the game later, the switch will have failed again.
Tightening the screws too tightly on the switch can damage the switch internals making the switch intermittent.
The switches in games that were played on location for many years simply wear out.
When micro-switches are damaged or past their useful lifetime, there is nothing to repair, adjust, or clean inside them. Simply replace them for reliable operation. You can purchase generic switch bodies and transfer the wireform carefully to the new body.
6.29.10 Switch Wiring
Williams switches are always wired the same. The white (plus tracer) colored wire (row) always attaches to the same solder lug as the NON-banded end of the diode. The green (plus tracer) colored wire (column) always attaches to a lug by itself. The banded end of the diode always attaches to a lug by itself. This creates the following circuit, shown schematically at left.
The picture gallery below provides an example of correct wiring for different types of switches.
- Connections for Various Types of Williams Switches
Slingshot Switch. The Green and White wires go off-frame to the other slingshot switch in the pair. 
Standup Target 
Typical Pop Bumper Switch 
Older Style Micro Switch 
The Pervasive Sub-MicroSwitch 
Reed Switches, as found in Cactus Canyon and NBA Fastbreak. The diodes are located elsewhere.
6.30 Display problems
Display problems are usually the result of failing dot matrix displays themselves, flakey ribbon cables or connectors, ribbon cables installed "one row off" (or even one column off), failing high voltage sections of the dot matrix controller board, and rarely logic IC problems on the dot matrix controller board.
Start by checking the easy things first...
- Reseat the narrow ribbon cable between the DMD controller board and the DMD.
- Reseat the wide ribbon cables from the MPU to the DMD controller.
- Ensure each ribbon cable is correctly mated, and not "one row off" or even "one column off".
6.30.1 Display Panel Problems
The display panel itself may have problems. The glass component has a limited life. The continued electrical discharge releases gases inside the display, which eventually stop the pixels from glowing, and the dots will slowly fade over time. If the voltages are too high, the panel will show sparkles, clouds or ghosting.
6.30.2 DMD Repair Warnings
Be careful when repairing the DMD Controller Boards, you are dealing with High Voltages when the boards are running. A good safety measure is to put one hand in a back pocket (or behind your back) when testing voltages.
It's also fairly easy to lift traces on the PCB or ruin the 'through holes' when removing components. If this happens, you may have to check continuity and 'stitch' the component hole with a thin wire strand. It's a good idea to practice on some useless PCB boards first, before taking on the DMD Controller Boards. For details on a stitch see the "How to Stitch" section of the Wiki.
If you do not have decent soldering and de-soldering skills, DMD HV work should be left to a professional.
HV Repair Kits and advice are available from: Ed at Great Plains Electronics
- WPC-95 HV REPAIR KIT
- WPC HV REPAIR KIT
- GPE kits do not contain capacitors, which can be ordered separately as needed.
HV Repair Kits and advice are also available from: Rob Anthony at Pinball Classics
- WPC-95 or WPC HV REPAIR KIT
- Indicate in the notes section of the order if you need the WPC or the WPC-95 HV kit, Pinball Classics kits do contain the 150µF 160V capacitors.
Bally/Williams and Data East have similarities with the 128x32 display and the display itself is interchangeable between manufacturers. DMDs have a limited lifetime and will eventually outgas. Please see the information about outgassing displays in the Data East section.
6.30.3 Testing DMD Controller Power
After you've checked the easy things, measure the voltages supplied by the DMD controller to the DMD display panel. To test the DMD controller voltages, first open the backbox, and rest the DMD panel face down on the glass. The simplest place to test the voltages provided by the DMD controller is at the display end of the power wire bundle as shown in the picture. SAFETY WARNING: Your left hand should be in your pocket, to avoid a potentially serious shock. We are working with high voltages, so be VERY CAREFUL. Keeping one hand in your pocket is a good practice to follow as it eliminates the easy electric current pathway across your heart. A DMD controller provides enough electric current to kill you!
Most high voltage problems are lack of the proper voltage levels. This results in no display at all. It is possible however, for the high voltage circuitry to fail in such a way that too much voltage is supplied. Or, a game might be jumpered for a lower expected voltage but connected to higher voltage. This manifests as a "plasma" or "cloudy" look on the display, as shown on the left. Note that this looks very much like an outgassed display.
If the display image has a "plasma" affect or a "cloudy" look, it's a good idea to test the input voltage to the DMD Controller board, as depicted in the animated image at left. Nominal voltages are 80VAC and 100VAC. If measurements indicate voltages significantly higher than the nominal voltages, ensure the voltage select jumpers are correct, as discussed here.
The dot matrix display needs three voltages to operate. Williams designed the DMD controller to drive the the DMD display panel just a bit below its specified voltages, presumably to extend the life of the panel. You can find the specification of a panel here.
Place the black lead of the DMM under the ground braid in the game's head or use clip leads to secure the black lead to ground. Remember, you are working one-handed, so this becomes a necessity. Place the red lead of your DMM on each of the pins supplying power as shown in the picture. At some point in the production of DMD controllers, Williams changed the Anode and offset voltages from about -124VDC and -112VDC to about -112VDC and -100VDC. As long as there is a 12VDC difference between the Anode and 12VDC offset voltages, your DMD controller is providing correct voltage levels.
| Function | J604 Pin | Spec | nominal WPC voltage | Notes |
|---|---|---|---|---|
| Anode | -124V in early DMD machines | |||
| 12VDC Offset | Must be 12V less than anode voltage. Will be about 20V less than anode voltage if display not connected | |||
| Key | ||||
| Ground | ||||
| Ground | ||||
| 5VDC | ||||
| 12VDC | ||||
| Cathode | Williams runs this voltage low |
If the high voltages are off by more than a few volts, turn the game off, disconnect the power connector at the DMD controller, and test the voltages at the DMD controller male header pins. If the voltages return to nominal WPC voltages, the zener diodes on the DMD controller are probably OK but the resistors and transistors around them are suspect. As shown in the table above, if DMD controller power is not connected to the display, the nominal 12VDC offset will be about 20VDC.
Note that a failing or failed DMD display glass can drag these voltages down. Before you begin any work on the DMD controller board, perform the above test with the DMD display power disconnected. If the voltages return to nominal WPC voltages, it's possible that your display is the culprit. Test the DMD controller with a known good display to isolate the fault to either the DMD controller or the display panel.
For the 62V and -112V circuits Williams used a relatively sophisticated regulator circuit. The problem is, the resistors and diodes dissipate quite a lot of heat. In a warm operating environment, this leads to burned components and circuit boards. The board traces are often weakened. Repair in the area is tricky.
Here's a description of the function of the parts in the -112V circuit.
Q1 is an output buffer. It just follows the voltage set at the top of zener diode D2. Q2 and Q3 form a constant current 5mA driver for the diode. Q2 is a current control for D2. By pulling on the base of Q2, the zener current can be reduced to compensate for the diode leaking as it warms. Q3 is a current sensor for D2. Note the very low 120 ohm resistor. If D2 passes more than 5mA, Q3 will start to turn on, and reduce the current through the diode by pulling on the base of Q3. So the zener diode always operates at 5mA.
The transistors can be tested in circuit, just watch out for the 120 ohm resistors across the base and emitter of Q3.
The board is subject to transistor shorts, which can also blow out the resistors. Open resistors are a common problem if Q2 and Q3 are bad.
Sometimes when you are missing a voltage, check resistors R3 and R6 (both are 47K 1/2W). Used for switching on the transistors Q2 and Q5
In the same spot are also R12 and R13, which are also 47K 1/2W. Used for discharging the capacitors C4 and C7.
A good thing is to replace all four resistors.
6.30.4 Slow Animations
Slow animations along with sound synced to the animation is a very unusual problem. It is caused by a manufacturing defect in pre-DCS sound boards. As shown at left, an imperfect solder mask led to a solder bridge connecting pins 31 (R/W, read/write) and 34 (FIRQ) on the solder side of the sound board. By connecting the FIRQ signal and the R/W signal, the whole system slows down due to extraneous FIRQ interrupts to the MPU ASIC. The correction for this is straightforward, remove the solder bridge.
A YouTube video of this problem can be found here.
A PinSide thread leading to this solution can be found here.
6.30.5 "SuperScript or SubScript" Characters
One of the more interesting display failures is the appearance of characters on some display formats that appear to be shifted up/down 1/2 character or SuperScripted/SubScripted. The cause of this failure is not the display or the dot controller. This failure is caused by a poor connection between the ASIC on the MPU board and it's socket. Reseating the ASIC generally solves this problem. You can "retension" the ASIC leads using this method provided by Ed at GPE.
- Super/Subscripted Characters
Superscripted characters... 
No Fear subscripted characters... 
Subscripted characters...
6.30.6 "Rolling" Horizontal Line on WPC-95 Display
This problem resembles an old CRT with a vertical hold problem. A wide horizontal line "rolls" through the display from top to bottom.
This problem is easily rectified by replacing C28 and C42 on the Audio/Video board. The original value of these radial capacitors was 150µF/160V. If the original valued capacitors can't be located, the more common 220µF/160V cap is a good replacement.
6.30.7 Outgassing Displays
- DMDs will eventually fail. It is important to replace an outgassing display as they place extra strain on the power supply, and will eventually damage the power supply. One sign of an outgassing display is that areas of the display need to 'warm up' before becoming fully bright or that the display will remain completely blank for a few seconds and then appear normal.
Outgassing displays look very much like a display that is being overdriven by too much voltage. The acid test is to measure the high voltage using the technique described later in this section.
6.30.8 Display is "delayed" after turn on
There are cases of import machines incorporating an aftermarket circuit that delays the DMD display from appearing for a fixed amount of time after the game is booted. This was done by some operators so that serial number and location information could not be ween when the machine is powered on, thereby preventing identification of a game and potential sales/operation outside a given geographic area. This circuit will not damage anything but is not standard. More information about this can be found in a rec.games.pinball discussion.
6.30.9 "Snow" on Display
"Snow" in this case means rapidly flowing, left to right, "sprays" of dots, almost like can be seen when "spraying" the gun while moving it left to right in Attack from Mars video mode, but much faster.
The cause of this in at least one case was found to be a failed 74HC74 (dual D-Type Flip-Flop) at U4. Pin 5 is the "serial clock" signal to the DMD display. Diode testing indicated that the gate had failed. Replacement of the IC returned the board to normal service.
6.30.10 Fuse F601 or F602 blows
The WPC DMD controller rectifies AC voltage via two small 1 amp bridge rectifiers. If a bridge shorts, generally the associated fuse will blow. Sometimes the current draw on the other side of the bridge is so great that the fuse blows too. Whatever the reason, the bridge can be easily tested using the same general bridge testing technique.
The pin layout for these small bridges is different from the larger 35A bridges on the power/driver board.
Begin with your DMM set to diode check, and the red probe on the leg marked with a negative sign as shown in the picture at left. Placing the black lead on each of the AC legs in turn should yield a reading between .5 and .7 volts. If your measurements fall outside of this range, replace the bridge.
Next, move the black probe to the leg marked with a positive sign as shown in the picture at left. Placing the red lead on each of the AC legs in turn should yield a reading between .5 and .7 volts. If your measurements fall outside of this range, replace the bridge.
A YouTube video showing how to perform this test can be found here.
Another reason for F601 to blow is shown at left. Some revisions of the DMD Controller routed the trace from one side of BR1's AC power to F601 too close to the lower right screw that secures the board to the backbox ground. If the star washer for this screw bites through the solder mask, this creates a direct path to ground, blowing F601, as it should. This can be corrected by either leaving the screw out, using a nylon washer, or using a nylon screw. Any of these three methods will work fine.
6.30.11 Schematic Diagram for WPC and WPC-95 DMD Controller Board
Schematic for DMD HV section WPC only (adapted from TZ manual, same as link below): WPC DMD HV
Schematic for DMD HV section WPC95 only (adapted from AFM manual): WPC95 DMD HV
Here’s a schematic with a list of the parts needed for both WPC and WPC-95 high voltage section repairs. the two boards are similar in the high voltage regulation sections.
Another area which will help with troubleshooting the DMD Controller Board can be found in the DE section of the PinWiki (DE copied the Williams board designs), Data East High Voltage Repair.
The following images of a fairly crispy WPC-089 DMD controller will assist you in ensuring that all traces are repaired.
- DMD Controller, High Voltage Section Parts removed
Front side traces. The yellow line shows where a trace had burned off of this board. 
Rear side traces.
6.30.12 Step-by-Step Repair Video
A video showing the steps necessary to rebuild the high voltage section of the DMD Controller can be found here.
6.30.13 Heat Damaged Trace Under R9
Resistor R9 eats a lot of current and becomes very hot, especially as the associated circuit components age. This damages the trace and PCB beneath it, sometimes to the extent that the trace is severed. "Buzzing" the connection between C4 and R11 is a simple test to ensure continuity of this trace.
6.30.14 Evenly Spaced Vertical Lines
Evenly spaced vertical lines with 8 columns between the lines can indicate a connectivity issue along a ribbon cable. Running the display test may show a "page error" message.
Example
Example during display test
First (and with the game turned off), try reseating every the ribbon cable connector along the full length of the ribbon cables that connect to the upper left side of the DMD controller.
If that doesn't resolve the issue:
- Try replacing the ribbon cable.
- Check for dirty, corroded, or broken connector pins on each of the ribbon cable headers on the DMD controller board, driver board, and MPU.
- Also check for cracked soldier joints on the header pins of each ribbon connector header on the DMD controller board, driver board, and MPU.
6.30.15 Failed RAM
Most failures of the DMD controller that are not attributed to the high voltage section are caused by failed 6264 static RAM at U24. Since the RAM is very susceptible to electrostatic discharge, they are often damaged by improper handling. Sometimes, they just fail. Failure of this RAM manifests in many ways, including some shown below. At the very end of "display test" the MPU performs a read/write test of the RAM. If the MPU is able to communicate properly with the DMD controller, writing to and reading from the 6264 at U6, then the message "RAM TEST OK" is shown on the display. Any other message indicates a failure of the test. Test failure may be due to the I/O buffers on either the MPU or the DMD controller, the ribbon cable, or the actual RAM.
A YouTube video of a successful display test can be found here.
6.30.16 Page Errors
There are 2 pages of 16 memory locations (0 to 15) stored in RAM on the DMD controller board. In the Display diagnostics it will run the page test and display any possible faults on either the low page or the high page (page 1 and 2 respectively) If you are only seeing errors on page 1, look to change out U33, most likely at least one output stuck high (pins 2,7,10,15). Page 2 errors the likely culprit is U35. Both devices are 74LS175. If you are seeing the same errors on both page tests, most likely it will be U16, a 74LS157, which is the A/B selector between the two page addresses.
Page errors will also throw up a RAM address error. The RAM is not at fault, just how it is addressed by the page selectors. It should clear after attending to the above
Note: the coin door buttons for advance/go back can be held down to quickly move through display test.
- Various display issues resulting from failed 6264 RAM on the WPC-089 DMD Controller board.
Example 1 
Example 2 
Example 3 
Example 4 
Example 5 
This random pattern caused by a blown 6264 RAM. It was blown by sending Flipper Coil power (nominally 70VDC) down the data lines (D0-D7). 
Example 7
6.30.17 Failures of Various Logic ICs on the DMD Controller
The following images represent various failures associated with specific ICs on the DMD Controller board. Of course, the specific way that an IC fails will influence what is displayed. That is, your mileage may vary.
U1 - 74HCT138 - evenly distributed non-moving "snow"
The display works in the game and attract-mode but in the test menu it shows nothing. U31 and/or U32 was defective. Think the opposite when the display shows nothing its worth to go into the test because possible it shows only the test.
When the display shows nothing but the data between U31 and U32 seems to be good and also there is data on BD0...BD7 to U29. Test Pin 2 of U29. If there is no clock then follow the line in the schematic to U20. There must be a clock at Pin 1. If no clock coming out from U17 Pin 9 the display shows nothing. After replace U17 the clock signal was there but corrupted from IC U4. After replace U4 too the DMD controller works.
The display shows nothing. The following lines send data to the display SERIAL_DATA SERIAL_CLOCK COLUMN_LATCH ROW-WRITE but ROW-DATA is static High or Low. U13 was defect.
6.31 Sound problems
Before going any further, check all of the basics in the Basic Sound Troubleshooting section.
6.31.1 Sound Board Interface Error
A "Sound Board Interface" error occurs when the MPU board can not communicate properly with the sound board at boot up. There could be several reasons for this problem.
- Ribbon connector not properly seated. The ribbon to the sound board(s) originates at J202 on the MPU board, goes to the FlipTronics board, then to the sound board (whether pre-DCS or DCS), then on to the DMD controller board.
- Failed ribbon cable. Due to over-flexing, the ribbon may have failed.
- Mismatched ROMs between the MPU and sound board. This isn't as big of an issue as with Data East games, but updating the game ROM to a newer version while leaving the sound ROMs at an older, even prototype version, could cause this problem.
- Solder bridges, or corrosion under the ribbon connector.
- Failed I/O buffer ICs on either the sound board or on the MPU board
On DCS sound boards, U18 buffers data from the MPU. U19 buffers data to the MPU. Testing these ICs using the this method should yield similar results to the values listed below. Note that this test method can't identify either a good or a bad integrated circuit with 100% certainty but using this test is preferable to removing chips unnecessarily. These readings were taken using a Fluke 179 DMM. Different meters, different manufacturers chips, and even individual variation in manufacture will probably cause your readings to be slightly different, yet consistently different. i.e. If the table shows .657 and your meter yields .630, then every pin listed at .657 should read close to .630 with your meter.
Probe pin 10 with the DMM red lead. Probe each of the other pins with the black lead.
| Pin | Diode Test Value U18 | Diode Test Value U19 |
|---|---|---|
The root cause of a "Sound Board Interface Error" on a Star Trek:The Next Generation game is shown at left. The corrosion on the trace leading to pin 28, created a conductive bridge to pin 29, which is a critical signal to the sound board (WDEN).
Another physical PCB problem pictured at left (but repaired), caused a "Sound Board Interface Error". The sounds on this board operated fine since the error was in the hardware that talks back to the MPU.
A similar problem can be the cut component lead just left above the yellow circle. If it is bend towards the printed trace and making contact, it can also manifest itself as the "Sound Board Interface Error".
6.31.2 Shorting the Speaker Leads or a Shorted Speaker
A blown sound amp will cause a loud buzz when the game is powered on. Generally, amps blow due to reduced impedance (aka resistance, ohms) in the speaker(s). If a speaker shorts, the associated amp(s) will blow. Or, if the drive connection (not ground) to a speaker breaks free of the speaker connection lug and touches ground with the power on, the associated amp(s) will blow. Note that the speaker metal housing is connected to ground.
The image at left shows two amps from the same WPC-95 AV board that were blown when the non-ground speaker wire broke free and touched the speaker housing. It is good practice to solder the speaker wires onto the speaker connection lugs to prevent this from every happening.
Diode testing is an effective method of determining that an amp is blown. Place the red lead of your DMM on the center leg of the amp and test each of the remaining four legs. Compare results to a known good amp of the same type. Generally, readings between .5 and .8 should be observed.
6.31.3 Lowering the Minimum Volume
By default the game volume can be set no lower than '8' to prevent an operator from setting the volume too low. This can be overridden by entering the adjustments menu and setting Adjustment 1.28 (Minimum Volume Override) to yes. You can now set the volume as low as you like.
6.31.4 High Frequency Sound Only
This applies to pre-DCS and DCS sound boards. Uncertain if AV boards apply or not.
There is a situation where only the tweeter / high frequency sound can only be heard. This will result in the game sounding much quieter than usual. Most speaker systems are parallel circuits. However, the woofer on a pre-DCS sound system is in series with the midrange speaker. The high frequency speaker is in a parallel circuit to the mid and low range speakers. If there is no sound from the woofer in the bottom of the cabinet, there will be no midrange from the speaker panel.
First, make certain that the speaker output wiring from the sound board is connected correctly. Also, there is a bullet connection located inline which must be connected. This bullet connections ties the low and midrange speakers in series. Finally, check the connections at the woofer in the bottom of the cabinet to make certain the female spade connectors are secured to the speaker terminals. If all connections are secure, there is a chance that the woofer speaker is blown.
6.31.5 Pre-DCS Sound Board Issues
The blue Philips 47µF 35v axial electrolytic capacitors on these sound boards are prone to failure, often testing with no capacitance or extremely high equivalent series resistance.
6.31.5.1 Power on Sound Tones (Bongs)
After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.
Pre-DCS Sound Board Games.
- 1 - No issues...enjoy a game.
- 2 - U9 RAM failure.
- 3 - U18 ROM failure.
- 4 - U15 ROM failure.
- 5 - U14 ROM failure.
6.31.5.2 No Sound at all
The highest probability reason for the complete lack of sound is connections to the speakers. The IDC connectors at J504 and J505 carry the sound to all speakers in the game. Since the speakers are connected in series on a pre-DCS game, any break in the speaker signal loop will cause loss of all sound. First check the small gauge wires at connectors J504 and J505. Since they are IDC connectors, they are prone to breaking free from the connector. Next ensure that all speaker connections are solid.
It is possible for a speaker to fail, commonly called "blown". You can test a speaker by applying anything from an AA battery to a 9V battery to the speaker terminals. You should see the speaker cone react when the battery is touched to the terminals.
6.31.5.3 Unbalanced Sound
Pre-DCS sound boards are not 100% interchangeable across games. Games from Funhouse to Party Zone (including Funhouse, Harley Davidson, Bride of Pinbot, Slugfest, Gilligan's Island, Terminator 2, Hurricane, and Party Zone) use different resistor values at R23/R24 than the remaining games that used the pre-DCS sound board (games from Hot Shots basketball through The Addams Family Gold). If you find the sound "unbalanced" between background sounds and voices, for instance, check the following resistor values.
R23/R24 values for...
- Funhouse through Party Zone - 150K ohms
- Hot Shots through TAFG - 56K ohms
- Funhouse through Party Zone - 150K ohms
Note that the resistor value indicated in the schematics for pre-DCS sound boards at R22 and R25 are wrong. The schematics indicate 150K ohms. The correct value is 120K ohms.
6.31.5.4 No Sound or Low Volume Sound from Right Speaker
As Joe "Tony" Dziedzic discusses here, "the back box speakers are wired in parallel, with a 10uf non-polarized capacitor in series with the right speaker (the tweeter). The capacitor is used to block lower frequency sounds from being reproduced by the speaker. Technically, the capacitor forms a first-order high-pass filter with a crossover frequency of 4000 Hertz. This configuration presents an effective impedance of around 4 ohms."
If the 10uf capacitor fails "open", then the signal to the speaker is open and the speaker will remain silent.
The repair is simple...replace the capacitor.
6.31.5.5 Distorted or slightly "off" sounds
The pre-DCS sound board uses 47µF capacitors as filters in the sound circuit; C15, C36, and C38. If one or more of these caps fail, certain sounds may not be as loud or as clear as intended. The game will just sound "off" with perhaps slightly unbalanced sounds. An amazingly high percentage of these caps fail. It is recommended that if your sounds are a bit "off" that you replace all of these caps.
Note: as shown at left, C38 is sometimes not stuffed at the factory. It appears that audio channel 1 and channel 2 (in C38s path) from the Yamaha YM3012 are redundant, making this cap unnecessary.
Also, some pre-DCS sound boards looked to have been "hacked" to add a ceramic capacitor just below the clock crystal X1. This is not in fact a hack. It appears to "fix" the omission of C49 on some versions of the PCB. C49 is located at the edge of the board, just above the crystal.
6.31.5.6 Popping, Scratchy Sound, Very Hot LM1875 Heat Sink, or Shorted Speakers
Sometimes, the tantalum/ceramic caps in the amp circuit fail too. This can result in too much AC "ripple" feeding the amp as well as DC output to the speakers, which they do not like. The following components are all suspect...
- C20 (10µF, 20V tantalum)
- C46 and C47 (both 1µF, 35V tantalum)
- C22 (22µF, 35v electrolytic)
- C23 (.22µF, 10V, ceramic)
Normally, the positive side of the tantalum cap at C26 will measure about 50mv of AC referenced to game ground. Anything more indicates a problem with these tantalum caps. You will also be able to measure DC voltage across the speaker outputs. There should normally be no DC voltage across the speaker outputs.
The LM1875 may also run very hot. Normally, you can grasp the heat sink without burning your hand. It will be hot, but not so hot that you can not squeeze it or grasp it very long. Note: this assumes that the volume is set to about 8. Setting the volume to 18 will require the heat sink to dissipate more heat. The heat sink will be too hot to grasp (for very long). If at "normal" volume levels and the heat sink is so hot that you can not grip it, failing tantalum caps should be suspected. If after replacing the tantalum caps the popping and scratchiness persist, the LM1875 amp may have been damaged.
6.31.5.7 Volume Not Adjustable and/or Stuck at Low Volume
This problem manifests as a very low volume from the speakers, equivalent to the lowest sound level setting. The volume setting may be adjusted from the coin door, and the DMD volume "thermometer" will move normally, but the speaker volume will not change. While the cause of this issue could be a failed digital POT as discussed here, a failed MC3340 electronic attenuator may also be the cause. You may be able to identify the MC3340 as the problem by comparing "diode test" results with a known good MC3340.
In one such case, pins 7 and 8 of the device where shorted together, causing the symptoms described. The failed MC3340 may also have caused the amp to become very hot, but this has not been conclusively proven.
Take care to ensure the MC3340 is actually at fault as this obsolete part is pricey and hard to find.
6.31.5.8 Volume at zero but still audible
If you set the volume to zero via the coin door buttons and you can still clearly hear it, there is a good chance that the axial capcitor C18 (47 µF, 10 V) is bad. If this capacitor fails, the output voltage of the digital pot U5 (X9503) might not go high enough to silence the sound completely. When the volume is set to zero, a voltage of approx. 3.5 V should be measured at U5 pin 7 or bridge W9 or U2 pin 2. Lower voltage will result in clearly audible sound even when set to zero.
6.31.5.9 Wrong sounds being played
Generally, this problem boils down to a communication problem between the MPU and the sound board. Possible failure points are:
- Ribbon cables
- Male header pins on both MPU and sound board
- 74LS374 data buffer ICs on the sound board used to communicate between the MPU and the sound board.
- Rarely, a failed 6264 RAM can cause this. The RAM is "tested" by the MPU. Sometimes it will pass the test, yet fail in game play. Odd...I know.
6.31.5.10 Volume Suddenly at Maximum
If the volume suddenly jumps to full volume and control of the volume via the coin door buttons does not work, check C18, a 47µF 35v axial electrolytic capacitor. The blue Philips capacitors on these sound boards are prone to failure and can cause this issue if bad. If that does not solve the problem there is a good chance that the digital POT (volume control) on the sound board has failed. The part is located at U5 and is an X9503. The X9503 is obsolete but it's successor the X9C503 works fine here.
6.31.5.11 Blown 1uF or 10uF Tantalum Capacitor
The pre-DCS sound board uses 1uf tantalum caps in the amp circuit. Sometimes, for no good reason than simply being old, one of these caps will explode and burst into flames at game power on. C46 on the board shown at left did just that. In the great majority of instances, simply replacing the cap returns the board to service. This "burning into flames" can also happen to the +12V and -12V section with C26 and C28.
When the 1uF tantalum at C27 or C29 shorts internally, it will cause the +12V or -12V to disappear. The LM7812 (U4) or LM7912 (U3) will run very hot. The tantalum draws all the current. The LM7812 and LM7912 have a limit of 1 Amp. The voltage will drop to zero when this happens, leaving the amplifier without power.
Other tantalum caps have been documented to explosively fail, including C28 and C47.
A tantalum capacitor can be tested by desoldering one leg and using a DMM (in diode check) to check for a short. Simply replacing the tantalum will solve the problem.
A contributing factor to these explosive failures was that the voltage rating on the capacitors that were used was too close to the operating voltage running through them (undersized components were typically used as a cost saving measure). As a general rule of thumb, the operating voltage should be 50% of the voltage rating of the tantalum capacitors. So, for a 12V circuit, at least a 25V capacitor should be used; a 50V minimum rating would be better.
All the tantalum capacitors used on the pre-DCS sound board are listed below:
- C20,C21: 10uF axial tantalum capacitor (original rating was 10V; use at least 35v instead).
- C26,C27,C28,C29,C37,C46,C47,C48: 1uF axial tantalum capacitor (original rating was 35V; use at least 50v instead).
Note that the tapered end is the positive side and also has a "+" symbol near it (however, with a burnt part, this might be impossible to see). Since the board was not silkscreened with any indications of component polarity, make note of the direction on the original part before removing it.
After replacing one blown tantalum capacitor, it is possible that a second power up might blow a different one. Therefore, it might be a good idea to preemptively replace all the tantalum capacitors, especially if one has already experienced an explosive failure.
The tantalum caps on this board can be replaced with the same rated (1uf) electrolytic caps. The two caps adjacent to the large heat sink need to be positioned to allow space for the large 4700uf caps also adjacent to the large heat sink.
6.31.5.12 Sound Is Very Faint Even at Maximum Volume (CVSD Failure)
While most techs would suspect either a TL082 or a TL084 amplifier (on a pre-DCS sound board) or a 1458 amplifier (on a System 11 MPU) as the cause of this issue, the 55516/55532/55536/55564 CVSD (Continuously Variable Slope Delta-Modulator) can also cause this issue.
Isolation to the CVSD is pretty simple.
- Place the game into sound test.
- Use an oscilloscope to probe pins 9 and 12. A scope must be used since the signals are too subtle for a logic probe to detect.
- Pin 9 is a clock signal.
- Pin 12 is a data signal.
When the game is making sounds that use the CVSD (generally voice calls), both pin 9 and pin 12 should show "off nominal" signals. If the CVSD is working correctly, the output at pin 3 should be showing signal also. If pin 3 is not showing signal, then the CVSD has failed.
During the run of the pre-DCS sound board, it is suspected that the 55536 CVSD part (and it's close cousins) was becoming hard/expensive to acquire. Williams created a "daughter card" to use in lieu of the CVSD. The daughter card used an MC3417 CVSD along with additional "tuning" resistors and capacitors. The sound quality result is indistinguishable from a 55536. Williams used a closed frame machine pin socket to accept the daughter card. The "chip notch" should be oriented just as you would the CVSD. That is, more of the card will be south of the chip socket than north of it.
While it might seem like a good idea to duplicate the design of this Williams card (part number 5768-14714-00) to replace the even harder to find 55536, the main part used, the MC3417, is equally hard to find today.
Jeri Ellsworth reverse engineered the 55564 (55536 equivalent) and posted this video in October, 2011. She makes it seem "intuitively obvious to even the most casual observer"...
6.31.6 DCS Sound Board Issues
The DCS sound board was used in 18 games including:
- Indiana Jones: the Pinball Adventure
- Judge Dredd
- Star Trek: The Next Generation
- Demolition Man
- Popeye Saves the Earth
- World Cup Soccer
- The Pinball Circus
- The Flintstones
- Corvette
- Red & Ted's Road Show
- The Shadow
- Dirty Harry
- Theatre of Magic
- No Fear: Dangerous Sports
- Indianapolis 500
- Johnny Mnemonic
- WHO Dunnit
- Jack*Bot
6.31.6.1 Power on Sound Tones (Bongs)
After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.
DCS Sound Board Games.
- 1 - No issues...enjoy a game.
- 2 - U2 ROM failure.
- 3 - U3 ROM failure.
- 4 - U4 ROM failure.
- 5 - U5 ROM failure.
- 6 - U6 ROM failure.
- 7 - U7 ROM failure.
- 8 - U8 ROM failure.
- 9 - U9 ROM failure.
- 10 - U10-U12 RAM error. Not always identified from the main CPU board program. DCS sound board RAM failures are indicated by a message on the display, "U10-U12 RAM error".
6.31.6.2 Very Loud Humming at Power On
The DCS sound board uses two 10,000µF caps at location C20 and C21 to smooth rectified AC power. The negative side of C21 and the positive side of C20 are connected to analog ground at header J4, pins 6 and 7. This connection is fragile. If the game hums really loudly, immediately at power on, test for continuity between these points as shown in the pictures below. Often this loud hum is diagnosed as a failing cap when the real problem is simply a fractured trace. If the caps have been replaced previously, there is a good chance that the PCB through holes have been damaged.
- DCS Sound Board Filter Capacitor Connections. Continuity is shown as a zero ohm connection.
The remains of through holes heinously ripped from a DCS sound board PCB. These "brown donuts" are still attached to the 10,000uf filter capacitor. 
The first of two tests ensuring continuity between the filter capacitors and analog ground. 
The second of two tests ensuring continuity between the filter capacitors and analog ground.
6.31.6.3 U10-12 RAM ERROR
Replacement RAM ICs for the DCS sound board are becoming harder to find. The board uses three, 2Kb skinny dip 6116 cache rams with an access time of 35nS or better. These are obsolete and long gone. The good news is that the board has jumpers for 6264 type 8Kb cache rams. Jumper W4 is installed for 2Kb rams. Jumper W4 should be removed and jumper W5 installed to use 8Kb rams. All RAM ICs need to be replaced at the same time for this configuration to work.
A relatively inexpensive, and still in production replacement, is the IDT 7164S20TPG.
RAM testers are not able to detect chips that do not meet the speed requirement. While slower RAM may pass chip test, it may fail on the board and cause the "10 bongs" error indication.
6.31.6.4 Muffled Sound and Speech/No Sound
Muffled audio can be caused by failure of the two 1uf/63V electrolytic capacitors that are in the audio circuit for each amplifier. Simply replacing them may clean up the audio. A typical 1uf/50V axial electrolytic capacitor will work fine.
It is also possible for one or both of these capacitors to fail completely open. In that case, no sound at all will come out of that capacitor's channel since they are in series with amplifier (C32 for the cabinet speaker and C41 for the backbox speakers.) Replacing the appropriate capacitor can restore sound to the silenced channel.
6.31.6.5 Volume Jumps to Max on Indiana Jones
The DCS sound board software has a bug in early versions that cause this issue.
Updating ROM S2 on the DCS sound board to the latest ROM revision will correct this.
6.31.6.6 Scratchy Audio or mumbled speech
During production of WPC-95 games, Williams removed two small ceramic caps (C47 and C51) from the A/V board to clean up the sound. This update should also be applied to the DCS sound board. On the DCS board C37 and C45 are the equivalent caps to be removed. Simply clip the caps from the board. You do not need to desolder them. This cleans up the sound and speech on some games like Demo Man quite well.
6.31.6.7 Notes regarding the TL084 part
The following was authored by Ed Krzycki, in a PinSide post here.
The suffix on these parts indicates how far off the output 'offset' can be. The offset is an added bias to the output voltage that is typically undesired in an audio device.
The offset is measured in millivolts. Higher the value, the more offset and the output is less 'true' to original input.
- TL084CN = worst case offset (standard part) = 20mV
- TL084ACN = 7.5mV
- TL084BCN = 5mV
- TL084IN = 9mV but has a much wider temperature 'industrial' temperature range.
The TL084BCN is better than the TL084ACN and the TL084ACN is better than the TL084CN.
The TL084IN is the same as the TL084ACN when used at normal room temperature. But the TL084IN version can withstand higher temps.
Any introduced DC voltage offset is typically removed if there is a capacitor in series with the output (common) but can still add a bit of distortion. Keep in mind that pinball sound boards are not exactly high end audio equipment so any of these TL084 parts will work with no noticeable difference. There are other components in the design that are far greater at introducing noise into the sound.
6.31.7 WPC-95 A/V Board Sound Issues
The WPC-95 A/V Board was introduced, along with the WPC-95 system, with Congo and was used through the end of the WPC game system run. WPC-95 games using the A/B Board are listed below. The sound ROM part number is shown in parenthesis.
- Congo (5343-50050)
- Attack from Mars (5343-50041)
- Safe Cracker (5343-90003)
- Ticket Tac Toe (not a pinball)
- Tales of the Arabian Nights (5343-50047)
- Scared Stiff (5341-15191)
- Junk Yard (5341-15403)
- NBA Fastbreak (5341-15418)
- Medieval Madness (5341-15451)
- Cirqus Voltaire (5341-15584)
- No Good Gofers (5341-15591)
- The Champion Pub (5341-15703)
- Monster Bash (5341-15931)
- Cactus Canyon (5341-15191)
Always check the speaker connections to the A/V board (J504 and J505) and the wiring at the speakers before assuming there is a problem with the board. The speakers themselves can go bad; you can do a quick "click test" with a D-cell battery and a set of jumper leads to rule out dead speakers. Disconnect the speaker connections at the A/V board and connect your battery jumper leads to the pairs of wires in the J504 and J505 connectors; you should hear a click from the speaker if it is good. If you don't hear the click try the connection at the speaker itself to rule out wiring issues.
The analog output of the A/V board feeds into a TLO84 op-amp (U1) that is configured as a pair of low-pass and high-pass filters; these are used to separate the low-frequency sounds (destined for the cabinet speaker) and the high-frequency sounds (destined for the back box speakers). These two channels - signified on the schematic as AUDIO_R (cabinet) and AUDIO_L (back box) feed into a pair of TDA2030AV amplifiers; U5 drives the back box speakers and U6 drives the cabinet speaker.
The outputs of U1B and U1C (pins 7 & 8) can be briefly connected with a jumper lead to help narrow down issues when one of the two channels is not working or has weak/distorted output. When the two pins are jumpered you should be able to hear approximately the same level of sound from the cabinet and back box speakers. (Use the T.7 diagnostic test to play sound clips for the game during your testing.)
6.31.7.1 On Board Voltage Regulation
The WPC-95 A/V Board "digital" side is powered by the same 5VDC that is regulated by the power/driver board. The "analog" side of the A/V board, specifically the two TL084s and the AD1851 D-to-A converter, all use +5VDC and -5VDC that is regulated by the 78L05 and 79L05 respectively. Four rectifying diodes provide about +/- 17VDC to these regulators. If the sound is low or scratchy, check these two voltages first. Both +5VDC and -5VDC can be easily measured at pins 4 and 11 of either TL084.
6.31.7.2 Power on Sound Tones (Bongs)
After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs. Note that if more than one sound ROM exhibits a checksum error, only the first failed ROM will be indicated. Once that failed ROM is replaced, the next failed ROM will be indicated upon subsequent boots.
Audio/Video Board Games (WPC-95).
- 1 - No issues...enjoy a game.
- 2 - S2 ROM failure. Note: Two bongs also occur if jumper W3 is IN on the MPU board, and the installed RAM size is 6264. If an NVRAM was just installed, check this jumper. See the section on jumpers.
- 3 - S3 ROM failure.
- 4 - S4 ROM failure.
- 5 - S5 ROM failure.
- 6 - S6 ROM failure.
- 7 - S7 ROM failure.
- 10 - U9, U10, or U11 RAM failure (see below)
A/V sound board RAM failures are indicated by a message on the display, either "U9-U11 RAM error" or "U10-U12 RAM error". This is apparently game software dependent. A/V RAM are, in fact, U9-U11. Apparently, this message wasn't updated in some of the software with the introduction of the A/V board.<
A Youtube video showing "10 Bongs" can be found here.
Should it become necessary to replace one of the skinny DIP RAM chips, in lieu of a 28 pin skinny DIP socket, two 14 pin sockets may be used. Align the sockets using the trick shown here.
6.31.7.3 Loss of One Channel
If one channel is out or weak/distorted try the jumper at U1 pins 7 & 8 noted above. If no change is detected in the sound output it is likely the associated TDA2030AV amplifier (U5 or U6) has failed. Before replacing the amplifier jumper a 1 MFD 63 volt capacitor across C38 and C39 in turn (observe polarity!) to rule out a defective coupling capacitor. If jumpering pins 7 & 8 of U1 significantly improves the sound levels it is likely that U1 itself has failed.
6.31.7.4 Scratchy Audio
Williams removed two small ceramic caps (C47, C51, pictured at left) later in the production run of AV boards. If your game's audio is just a bit scratchy, and these caps have not been removed, you may be able to improve audio quality by removing them. Simply clip both sides of the cap. There is no real need to desolder them.
6.31.7.5 Really Loud buzzing sound for a second or two
If your game sometimes produces a really loud buzzing sound at random, check the version of your S2 sound rom. This problem was fixed with the latest S2 sound ROM for Attack from Mars, Congo, Safe Cracker and Tales of the Arabian Nights. Scared Stiff might also be affected but no version history for sound 1.1 exists for this game. Later games are not affected.
6.32 Flipper Problems
In most instances, an inexperienced tech will immediately blame the flipper coil itself for weak or non-functioning flippers. It is logical to blame the coil for the source of the problem. The flipper coil is, after all, the end reason why a flipper becomes engaged. However, its failure is the least probable reason that a flipper is not working.
6.32.1 Flipper does not work
In this case, you've started a game, you press the flipper cabinet switch, and nothing happens.
The first thing to do is inspect the wire connections to the flipper coil lugs. The most common reason a WPC flipper does not function is that either one of the wires broke from the game to the lug, or one of the coil winding wires, has broken away from the coil lug and is no longer connected to the coil. This is a pretty simple fix. Make a clean cut to the wire, strip or sand 1/4" to 3/8" of insulation back, and make a nice solder joint on the coil.
Some WPC-95 titles used "spade connectors" (also known as FASTON connectors) to attach wires to the coil lugs. This was done for ease of manufacture and for that reason only. Similar to a wire breaking free, these spade connectors sometimes do not provide a solid connection and sometimes simply fall off. In that case, cut the spade connector off and solder the wire directly to the coil lug. This makes a much better connection that is also much more reliable. Should a spade connector fall onto an adjacent coil lug, it's very possible that a short circuit will be created, possibly damaging the FlipTronics board.
6.32.1.1 Mechanical Reasons
There are a couple of mechanical reasons a flipper may not be working, including:
- Broken flipper link
- Flipper crank not "biting" flipper shaft (this would most likely manifest as a flipper that continues to move backwards, out of adjustment)
Simple inspection of the flipper mechanism should guide your corrective actions.
6.32.1.2 Pre-FlipTronics Games Electrical Reasons
- Failed flipper power supply - make sure that DC flipper power is present at the coil using your DMM. Place the red lead on a coil lug, the black lead on game ground (siderail or ground braid anywhere in the game). You should read about 70VDC.
- Flipper cabinet switch not "making" or fouled so badly that it doesn't conduct flipper power
- Fouled or missing flipper end-of-stroke switch. Pre-FlipTronics games relied on EOS switches in the same way that older games do. That is, power is routed to the power stroke winding of the coil via the EOS switch. If the EOS switch is fouled, only the hold winding will receive power; perhaps inadequate to move the flipper at all.
6.32.1.3 FlipTronics Games Electrical Reasons
- Failed flipper power supply. Flipper power originates at the transformer. It is routed through the power/driver board (which does nothing to it) and then to the FlipTronics board. The FlipTronics board rectifies the AC power via an onboard bridge rectifier. Power may be interrupted anywhere along this path, including a failed bridge rectifier or blown fuse.
- Failed flipper coil "power stroke" winding
- Flipper cabinet switch not "making" or flipper opto board not working
- Damaged connection between flipper cabinet switch and FlipTronics board
- FlipTronics board not recognizing flipper cabinet button switch closure
An unusual reason for the flipper switch closure signal not being sent to the MPU is shown at left.
- Failed logic path on the FlipTronics board including the transistors. See: WPC FlipTronics I and II Boards for a description of the signal path.
- Improperly seated or failed ribbon connectors between MPU and FlipTronics board
6.32.2 Flipper is weak
In this case, the flipper makes a stroke, but it's a weak stroke, not striking the ball with normal force.
6.32.2.1 Mechanical Reasons
- Not enough vertical movement in flipper bat (crank tightened too close to bushing)
- Cracked, broken or egged flipper bushing
- Mushroomed coil stop and plunger (replace coil sleeve too)
- Missing link bushing or oval link "eyelet"
- Tired flipper crank (will not tighten on bat shaft)
6.32.2.2 Pre-FlipTronics Games Electrical Reasons
- Flipper cabinet switch not "making" or fouled so badly that it does not conduct
- Failed flipper end-of-stroke switch
6.32.2.3 FlipTronics Games Electrical Reasons
- Dirty flipper cabinet switch optos
- Power stroke winding of coil failed
- Failed or partially failed bridge rectifier on the FlipTronics II board or on the 50V power supply board as used in The Addams Family
6.32.3 Flipper locks on or fails to fall to resting position
In this case, the flipper locks in the up position, either at game power on or when the flipper cabinet switch is pressed.
6.32.3.1 Mechanical Reasons
6.32.3.2 Pre-FlipTronics Games Electrical Reasons
6.32.3.3 FlipTronics Games Electrical Reasons
- Flipper cabinet switch opto interupter not returning to proper at rest position
- Sticky flipper buttons, which can lead to opto interupter not returning to at rest position.
6.32.3.4 Fodder (may be useful to complete this section)
- Fouled or broken "normally closed" EOS switch
- Fouled or broken flipper cabinet switch
- Flipper relay not enabled
- Fouled / dirty or non-functioning flipper opto switches
- Upper flipper switch closures in switch test, when there aren't any upper flippers on game
7 Parts Substitutions & Replacements
8 Repair Logs and Game Specific Problems and Fixes
Since WPC games are overwhelmingly the most popular pinball titles at the moment, and there are a vast amount of titles with so many game specific issues, please refer to the Game List section of this guide. Click on the specific game, and a new page will open regarding repair logs and game specific problems and fixes for that particular game title.
8.1 World Cup Soccer locks on Right Sling and both Left and Right Kickout Holes at Power On
- Problem
Upon power on, and with the coin door closed (defeating the high voltage interlock switch), the right slingshot as well as the left and right saucer kickout hole coils lock on.
- Cause
The flash lamp drive connector that should be connected to J124 is instead connected to J128.
- Discussion
Connecting the female plug to the wrong header pins is entirely possible since the connectors are the same width and are keyed identically. In World Cup Soccer (at least), the wire bundle is long enough to be connected (properly) to J124 or (improperly) to J128 or J132.
8.2 S2 Sound ROM Failure on WPC-95 After a Successful Boot
If game is turned on and has a successful boot, but after a few minutes, the game bongs twice indicating an S2 sound ROM failure and becomes unresponsive, try reseating the ASIC chip on the MPU. Make sure to use the proper removal tool and not a screwdriver. Using an improper tool will damage the chip and/or socket.