Gottlieb System 80

Note: This page is a work in progress. Please help get it to a completed state by adding any useful information to it.

1 Introduction

Gottlieb System 80 Board Set - 1st Generation

Gottlieb's second generation of solid state pinballs is System 80. Capabilities were increased in terms of controllable lamps, solenoids, gameplay, and sound. No longer tied to an EM-esque platform, Gottlieb started to introduce games with more unconventional asymmetric playfields. System 80 marked a foray into double and triple level playfields, speech, multiball; unfortunately, it also represented a step backwards in reliability, with battery corrosion, connectors, and bad grounding plaguing the design.

Once a system 80 game has been methodically gone through with board design grounding flaws and connectors corrected, they are just as reliable as any of their contemporaries.

Gottlieb System 80 Board Set - 2nd Generation

Gottlieb System 80A Board Set

Gottlieb System 80B Board Set - Early

Gottlieb System 80B Board Set - Typical

2 Games

2.1 System 80 1st Generation

Title	Date of Release	Production#	Model #	Sound	Notes
The Amazing Spiderman	05-1980	7625	653	Sound only - Media:Gtb_sys80_sound.JPG
Panthera	06-1980	5220	652	Sound Only - Media:Gtb_sys80_sound.JPG
Circus	06-1980	1700	654	Sound Only- Media:Gtb_sys80_sound.JPG	Ultra Widebody
Counterforce	06-1980	3870	656	Sound Only- Media:Gtb_sys80_sound.JPG
Star Race	08-1980	870	657	Sound Only- Media:Gtb_sys80_sound.JPG	Ultra Widebody

2.2 System 80 2nd Generation

Title	Date of Release	Production#	Model #	Sound	Notes
James Bond	10-1980	3625	658	Sound only - Media:Gtb_sys80_sound.JPG
Time Line	12-1980	3167	659	Sound Only - Media:Gtb_sys80_sound.JPG
Force II	12-1981	2000	661	Sound Only- Media:Gtb_sys80_sound.JPG
Pink Panther	03-1981	2840	664	Sound Only- Media:Gtb_sys80_sound.JPG
Mars God of War	03-1981	5240	666	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	First Gottlieb with speech, lane change, and multi-ball
Volcano	09-1981	3655	667	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG
Black Hole	10-1981	8774	668	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	First Gottlieb with 2-Level playing area, Export games used sound only board
Haunted House	06-1982	6835	669	Sound Only - Media:Gtb_sys80&a_s&s.JPG	First game with 3-Level playing area, Sound only, but used sound & speech board
Eclipse	1982	193	671	Sound Only- Media:Gtb_sys80_sound.JPG	Production game and available as a kit for James Bond 007

2.3 System 80a

Title	Date of Release	Production#	Model #	Sound	Notes
Devil's Dare	08-1982	3832	670	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	Export games may have used the sound only board - someone please confirm
Caveman	09-1982	1800	PV810	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	Pinball / Video game hybrid
Rocky	09-1982	1504	672	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG
Spirit	11-1982	1230	673	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	Sound only, but used sound & speech board
Punk!	12-1982	959	674	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	Sound only, but used sound & speech board
Striker	11-1982	910	675	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG	Sound only, but used sound & speech board
Krull	02-1983	10	676	Unknown
Goin' Nuts	02-1983	10	682	Unknown
Q*bert's Quest	03-1983	884	677	Sound & Speech - Media:Gtb_sys80&a_s&s.JPG
Super Orbit	05-1983	2100	680	Sound Only - Media:Gtb_sys80&a_s&s.JPG	Sound only, but used sound & speech board
Royal Flush Deluxe	06-1983	2000	681	Sound Only- Media:Gtb_sys80&a_s&s.JPG	Sound only, but used sound & speech board
Amazon Hunt	09-1983	1515	684	Sound Only- Media:Gtb_sys80&a_s&s.JPG	Sound only, but used sound & speech board. Later production games used piggyback sound board
Rack 'Em Up!	11-1983	1762	685	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Ready... Aim... Fire!	11-1983	390	686	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Jacks to Open	05-1984	2350	687	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Alien Star	06-1984	1065	689	Sound Only - Media:Gtb_sys80a&b_sound.JPG	689A Denotes a revision in the ROM code
The Games	08-1984	1768	691	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Touchdown	10-1984	711	688	Sound Only - Media:Gtb_sys80a&b_sound.JPG
El Dorado City of Gold	09-1984	905	692	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Ice Fever	02-1985	1585	695	Sound Only - Media:Gtb_sys80a&b_sound.JPG

2.4 System 80b

Title	Date of Release	Production#	Model #	Sound	Notes
Chicago Cubs Triple Play	05-1985	~1365	696	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Bounty Hunter	07-1985	1220	694	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Tag Team Pinball	09-1985	1220	698	Sound Only - Media:Gtb_sys80a&b_sound.JPG
Rock	10-1985	1875	697	Sound Only - Media:GTB Sys80B Sound.JPG
Raven	03-1986	3550	702	Sound Only - Media:GTB Sys80B Sound.JPG
Rock Encore	04-1986	245	704	Sound Only - Media:GTB Sys80B Sound.JPG	Production game using same playfield art as Rock, but mainly available as a conversion kit for Rock
Hollywood Heat	06-1986	3400	703	Sound Only - Media:GTB Sys80B Sound.JPG
Genesis	09-1986	3500	705	Sound Only - Media:GTB Sys80B Sound.JPG
Gold Wings	10-1986	3260	707	Sound Only - Media:GTB Sys80B Sound.JPG
Spring Break	04-1987	3550	706	Sound Only - Media:GTB Sys80B Sound.JPG
Monte Carlo	02-1987	4315	708	Sound Only - [[Media:GTB Sys80B Sound.JPG]
Arena	06-1987	3099	709	Sound Only - Media:GTB Sys80B Sound.JPG
Victory	10-1987	3315	710	Sound and speech - Media:Gtb sys80b MA886 sound.JPG
Diamond Lady	02-1988	2700	711	Unknown
TX Sector	03-1988	2336	712	Sound and speech - Media:Gtb sys80b MA886 sound.JPG
Robo-War	04-1988	2130	714	Unknown - - Media:Gtb sys80b MA886 sound.JPG
Excalibur	11-1988	1710	715	Unknown -- Media:Gtb sys80b MA886 sound.JPG
Bad Girls	11-1988	2500	717	Sound and speech - Media:Gtb sys80b MA886 sound.JPG
Big House	04-1989	1977	713	Sound and speech - Media:Gtb sys80b MA886 sound.JPG
Hot Shots	04-1989	2342	718	Sound and speech - Media:Gtb sys80b MA886 sound.JPG
Bone Busters Inc.	08-1989	2000	719	Sound and Speech - Media:Gtb sys80b MA886 sound.JPG	Used 3 sound boards

Game date of release, production numbers, and model number provided by the Internet Pinball Database - http://www.ipdb.org

3 Technical Info

3.1 System 80 / 80A / 80B Board Set

3.3 The Wiring Color Code

Unlike every other pinball manufacturer, which adopted a two-color wiring code system, Gottlieb used three colors. Most wiring in a Gottlieb game used a white base color, which is the wire's insulation color, and three "striped" traces on each wire. I state most cases, because there are some wires which only used two colors - the green insulated ground lines which have a single yellow trace, or only one color - the white ground wires used in System 80B games with no trace at all. Below is the Gottlieb color chart.

#	Color
0	Black
1	Brown
2	Red
3	Orange
4	Yellow
5	Green
6	Blue
7	Purple
8	Gray
9	White

Does the color chart look familiar? Well, if you have an electronics background, it should. The Gottlieb wire code system is the same as the resistor color coding system.

Here are some examples of the color coding system. The color wire code for switch strobe line 0 is 400. 400 would be a white insulated wire with a yellow trace and two black traces, or commonly referred to as a yellow-black-black wire. The ground lines in early System 80 games are code 54. 54 would be a green insulated wire with one yellow trace.

There is one word of caution, which should be pointed out. If the connections on A1-J2 and A1-J3 are being replaced, there are wire colors on these connections which are very similar. Although each wire is located on a different housing, please proceed with caution, as it can be difficult to see all three traces without spinning the wire around. The wires which come to mind are 344 and 677 on A1J2, and 433 and 766 on A1J3.

3.4 Switch Matrix

The Gottlieb System 80 / 80A / 80B switch matrix consists of a maximum of 64 switches. There are a total of 8 switch strobes and 8 switch returns. However, not every switch in the matrix is used on every System 80 game.

Just like the System 1 switch numbering system, the System 80 switch numbers have a similar naming convention. Except, the System 80 switch numbering system is the opposite of System 1. If you are accustomed to working on System 1 games, pay close attention. With Gottlieb System 80 switches the first number of the switch is its strobe number, while the second number is switch's return number. An example would be switch 54. Switch 54 is located on strobe 5 and return 4 of the switch matrix.

	Strobe 0 (A1J6-1 / A1J5-2)	Strobe 1 (A1J6-2 / A1J5-3)	Strobe 2 (A1J6-3 / A1J5-4)	Strobe 3 (A1J6-4 / A1J5-5)	Strobe 4 (A1J6-5 / A1J5-6)	Strobe 5 (A1J6-6 / A1J5-7)	Strobe 6 (A1J6-7)	Strobe 7 (A1J6-8 / A1J5-9)
Return 0 (A1J6-10)	00	10	20	30	40	50	60	70
Return 1 (A1J6-11)	01	11	21	31	41	51	61	71
Return 2 (A1J6-12)	02	12	22	32	42	52	62	72
Return 3 (A1J6-13)	03	13	26	33	43	53	63	73
Return 4 (A1J6-14)	04	14	24	34	44	54	64	74
Return 5 (A1J6-15)	05	15	25	35	45	55	65	75
Return 6 (A1J6-16 / A1J5-8)	06	16	26	36	46	56	66	76
Return 7 (A1J6-17 / A1J5-1)	07	17	27	37	47	57	67	77

3.4.1 The "Missing" Gottlieb System 80 Switches

With the Gottlieb System 80 series of games, there are some switch assignments that are designated the same throughout the System 80, 80A, and 80B platforms. These switches are typically not listed in the switch matrix portion of the manual. You have to review the cabinet schematics, and decipher what switches use what return and strobe. However, it appears that Gottlieb / Premier changed this section of the schematic starting with Excalibur or Bad Girls by no longer listing the strobes for these switches. So, below are the "missing" switch assignments for any Sys80B. All the info applies for Sys80 and Sys80A, except the two advance buttons, which weren't used prior to Sys80B.

06 - left advance button (Sys80B only)

07 - play / test switch

16 - right advance button (Sys80B only)

17 - left coin switch

27 - right coin switch

37 - center coin switch

47 - replay button

57* - plumb bob and ball roll tilts (these have the same switch assignment as the playfield tilt switch)

• Black Hole is one exception. The switch assigned for the tilt on Black Hole is 26.

Note: The coin door slam switch is not part of the switch matrix.

3.4.2 Setting up a Game for Free Play

Early Gottileb solid state pinball machines, prior to 1990, did not have a free play option available within the game settings. With this simple modification, a game can be set up for free play. First, identify the diode strip in the bottom of the cabinet. Once the diode strip is found, locate the credit button and coin switch strobe line wires. The wires will be located on the left of the diode strip - the non-banded side of the diodes. Below is a list of the wires.

Credit button wire - Green-Yellow-Yellow

Left coin switch wire - Green-Brown-Brown

Center coin switch wire - Green-Orange-Orange

Right coin switch wire - Green-Red-Red

Gottlieb System 80 Transformer Board

Solder a small lead wire from the credit button wire to any of the coin switch wires. Make certain that the diode, credit button wire, and coin switch wire are still soldered securely to the diode strip terminal when finished. If soldering is not an option, use a small alligator clip test lead. Now, when the credit button is pressed, a credit will be incremented and decremented. A game can be easily started without the need to open the coin door to trip the coin switches anymore.

Please note that this modification does not apply to Gottlieb System 80A and System 80B machines. System 80A and 80B machines use diode boards with edge connections, which are typically located on the cabinet wall near the left flipper cabinet switch. In my experience, jumpering the diodes on System 80A and 80B games do not give the intended free play results of jumpered System 80 diodes. I attribute this to the System 80A and 80B software reading the switch matrix differently.

3.6 CPU Board

The System 80 CPU board is a 6502 based microprocessor system. The 6502 microprocessor (the very same one used in the first Apple computer) executes the system BIOS out of U2/U3. This game code is augmented by PROM(s) at positions PROM1 and (possibly) PROM2. "Scratchpad" memory is added via a 5101 8Kx8bit CMOS memory. Control of peripheral devices (in this case lamps, solenoids, switches and sound) is accomplished via three 6532 RIOTs (RAM-I/O-Timer). Each RIOT in turn controls it's own "subsystem" to drive these devices.

Reset section

Switch matrix

Solenoids and Lamps

Displays

3.7 Driver Board

The System 80 Driver Board

The System 80 Driver board is responsible for all controlled lamps, relays, and all solenoids in the game. The CPU controls the driver board operation via a simple interface between A1J4 on the CPU and A3J1 on the driver board. Although the driver board went through some minor changes over the years, the same board can be adapted for all of the System 80 platforms.

To control the games' total of 51 lamps, the interface provides "device select" signals for each of the 74175s (Quad-D Flip-Flops) on the driver board, and 4 "bits" of data that is loaded (or "clocked") into a particular 74175 via the aforementioned device selects. Each lamp is driven discretely by a particular output of a particular 74175, which in turn drives an MPS-A13 or MPS-U45 transistor, (NDS-U45 transistors were used in place of MPS-U45s in some cases). Gottlieb did not implement a "lamp matrix" as some other manufacturers did.

It is noteworthy that there are some dedicated lamp transistors, which control specific game relays across the System 80 / 80A platforms. Relays such as the game over, tilt, and coin lockout relays are controlled by Q1, Q2, and Q3 respectively. The tilt and game over relays use the same designation for the System 80B platform, however, the use of a coin lockout relay was abandoned by this time. One neat feature of the driver board circuitry is that lamp "n" is driven by transistor Q"n+1". i.e. L12 is driven by Q13.

To control the games' solenoids, the driver board uses signals directly from the CPU to enable transistors on the driver board which turn on up to 9 solenoids. For solenoid control, the driver board uses MPS-U45, 2N3055, and 2N6043 transistors. Starting and ending with the System 80 platform, (games from Spiderman to Haunted House), three transistors were reserved to drive optional mechanical coin counters. These mechanical coin counter solenoids and associated transistors are: solenoid 3 (Q54), 4 (Q55), and 7 (Q56). Starting with the System 80A platform, (Devil's Dare), these transistors were no longer reserved for coin counters, and were used for other functions.

The games' sound signals (S1, S2, S4, S8) also pass through the driver board at Z14, a 7404 Hex Inverter. See below for S16 and S32.

Repurposed Driver Board Circuits:

A Typical Remote Transistor Mounted Under the Playfield

Since quite a few System 80 games employ more than 9 solenoids, and since the original driver board design will drive a maximum of 9 solenoids, Gottlieb repurposed some lamp outputs to drive "under-playfield transistors" which drive additional solenoids.

A Typical Transistor Driver Board

Once playfields became littered with numerous "under-playfield transistors", Gottlieb opted to merge some of these transistors into a transistor driver board. The transistor driver board started to appear on Gottlieb games nearly midway through the System 80B platform, with the game Victory.

The sound S16 and S32 signals are also repurposed lamp outputs. For instance, Haunted House and Black Hole both repurpose L9 to S16. Robo-War repurposes lamp 4 to S16. Note that S16 is not consistently implemented across the System 80 family. Note also that references to the usage of S32 are difficult to find.

3.10 Displays

3.10.1 System 80 - 6 Digit Displays

3.10.2 System 80A - 7 Digit Displays

3.11 Bookkeeping & Diagnostics

Gottlieb System 80 Coin Door Test Button Highlighted

To enter the bookkeeping/diagnostic mode, open the coin door and press the micro switch. (Note this switch has no credit function) The credit display will now show "00", then press the start switch and the CPU will enter its diagnostic mode (or press the self test switch again for bookkeeping.) Pressing the self test switch will advance it to the next test.

Bookkeeping (System80 only!)
1 Coins thru left chute
2 Coins thru right chute
3 Coins thru center chute
4 Total plays
5 Total replays
6 Game percentage
7 Extra ball
8 Total tilts
9 Total slams
10 Times HGTD has been beaten
11 First high score level
12 Second high score level
13 Third high score level
14 High game to date score
15 Average playing time

Diagnostics
16 Lamp output test
17 Coil output test (will cycle and display #)
18 Switch test. (99 = no fault) You can also check switch numbers by pressing them on the playfield now.
19 Display test. Displays will cycle through numbers
20 Memory test. (99 = no fault)

You can trigger the slam switch, tilt switch or wait 60 seconds to reset the CPU back to play mode. (This is why my slam switch is still functional!)

4 Problems and Solutions

4.2 Power Problems

Bridges, orange cap in cabinet

4.3 MPU boot issues

4.3.1 Relocating the battery from the MPU board

The first thing you should do to any System 80 MPU is remove the rechargeable NiCad battery from the MPU board. All batteries leak. It's simply a matter of when they will leak. A leaking battery will damaged your (sometimes irreplaceable) board.

There are at least four methods of relocating and/or replacing the battery on your System 80 MPU.

• You can remove the battery completely and not replace it. The 5101 memory will not persist from power-up to power-up and therefore, high scores, replay levels, and credits will be lost.

Remote Battery

• You can mount a remote battery pack that uses standard AA batteries (x3) to protect your board. You must also incorporate a blocking diode (1N4001, although a 1N4004 will work just as well) to prevent the game from attempting to charge the batteries. Install the blocking diode in series with the positive lead of the battery pack, with the band oriented toward the MPU.

Here a 5.5V, 1F Super Cap is used to retain 5101 memory for up to 30 days

• You can replace the battery with a 1F 5.5V "SuperCap". The capacitor will never leak, will charge during power-on cycles, and will retain 5101 memory for about 30 days.

• You may remotely mount a replacement NiCad battery in a location that, should it leak, damage to valuable circuit boards will not occur.
  

4.3.2 Repairing Alkaline Corrosion

A System 80 MPU with alkaline damage repaired/cleaned. Reset circuitry replaced with the much simpler Dallas Maxim 1811

If you find that the battery has leaked, alkaline damage can be cleaned up, traces repaired, and new components installed with kits available from several sources, including Great Plains Electronics.

An alternative to replacing a great many of the components is to use the Dallis/Maxim DS1811 reset generator. The DS1811-10 has a typical trip point of 4.35VDC. You may also use the Microchip Technology equivalent, part number MCP130-450DI/TO, available from Great Plains Electronics.

4.3.3 Slam Switch Modification

In order to test the CPU board on the test bench, a modification must be made to the CPU board to make the CPU think that the slam switch is closed. If the CPU thinks that the slam switch is not closed, the CPU will not complete the boot process, instead booting into a mode where the displays flicker all zeros at a very rapid rate.

Gottlieb designed the slam switch as a normally closed switch. That is, the switch must be closed for the machine to operate normally. When a brute kicks the machine, the slam switch will open from the inertial force on the weight attached to the switch, and the slam switch will open. Since the CPU is on the bench, we need a way to have this switch closed at all times to properly test the board.

Additionally, slam switches themselves fail. It's a good idea to implement this change as a preemptive fix for slam switch failures.

Slam Switch Mod

The slam switch can effectively be permanently closed by making a small solder bridge across two traces to the right of Z26 (which is on the lower right side of the CPU board). To permanently close the switch, remove the solder mask by scraping with a sharp knife or screwdriver. Create the solder bridge between the two now bare traces. This change will connect pin 13 of Z26 to ground, permanently closing the switch.

Alternative Slam Switch Mod

An alternate method of achieving the same results is to solder a clipped resistor leg across the bottom of capacitor (C30) and resistor (R20), both immediately to the left of Z26.

Keep in mind that the last 4 Gottlieb System 80B games were released with normally open slam switches. Do not perform the slam switch modification on these games. This includes the following games:

• Bad Girls
• Big House
• Hot Shots
• Bonebusters, Inc.
  

4.3.4 Connecting a logic probe to the MPU

A great place to source power for your logic probe while diagnosing the board is across the filter capacitor just to the right of connector J1. Connect the black lead of your logic probe to the negative (bottom) lead of the capacitor. Connect the red lead of your logic probe to the positive (top) lead of the capacitor. Take care to ensure that the clips don't short to adjacent components.

4.3.5 Using a PC Power Supply For Bench Testing

Future Update****This section works for now, but we can generalize bench power supply construction here: Building a flexible power supply for bench testing PCBs

The MPU board is much easier to work on if it is removed from the backbox and placed on the test bench. An AT-style PC power supply can be used to power the MPU board on the bench.

Obtain an old PC power supply. If you don't have an old computer laying around, head on off to the thrift store and pick one up. Remove the power supply from the case by unscrewing the appropriate screws. Be careful not to unscrew the power supply case itself.

Power Supply

Clip one of the connectors from the power supply wire bundle and clearly mark on the power supply box the value of each of the colored wires from the power supply. Typically, the yellow wire is 12V, red is 5V, and the black is ground. Strip insulation from the end of the red wire and the black wire as the System 80 MPU requires only 5V and ground to boot. Use alligator clips to connect 5v and ground to the appropriate J1 connection. I use larger alligator clips to make the connection easier.

J1 Connector

Mark connector J1 where the positive and negative (common) connection is for the five volts from the computer power supply. The ground connection is on the top of the connector, the 5V connection is on the bottom. The image shows A1J1 with the markings. I took the picture with the board still mounted in the machine. Connect the 5v supply with alligator clips to the positive connector on J1 and the black wire (ground) to the negative connector of J1. That's it! you're good to go! --Kencaine 02:30, 24 April 2011 (BST)

4.12 Updating a dual game PROM MPU (1st generation) to a single game PROM configuration (2nd generation)

As noted earlier, the first five system 80 games used both sockets at PROM1 and PROM2, populating them with 8K byte masked ROMs. Should one of these ROMs fail, you may be able to find a replacement, but they are becoming more pricey, more difficult to find, and are still prone to failure as they age.

A more flexible solution would be to update the MPU to use a single 2716 UVEPROM at the PROM1 socket.

Modifications must be made to both the solder side and the component side of the board.

Component side modifications:

Solder side modifications:

Your MPU board is now configured for any System 80 (but not 80A or 80B) game. All that remains is to acquire a 2716 EPROM containing the game's code.

4.13 Using a 2732 game PROM in a System 80B MPU

Need a jumper from TC1 pin x to J3, IIRC...need to verify...Chris Hibler

5 Game Specific Problems and Fixes

Example would be servo controller on Independence Day pinball

6 Repair Logs

Did you do a repair? Log it here as a possible solution for others.

6.1 Game Displays 000000 On Power Up and It's Not The Slam Switch

If you power the game on and all of the displays immediately display all zeros without strobing the problem is usually with the slam switch. However, if the slam switch modification has been done or the slam switch is working properly there is a problem with the switch matrix.

I had this problem on my Haunted House machine. I finally found that chip Z15 (7432) was bad.

I was fixing a kicker solenoid on the playfield, the playfield was still in the machine and fully in the upright position. While I was soldering the wire to the new solenoid I did not adequately protect the components below from a solder drip. Well, I did have a solder drip that landed right on a pop bumper driver board connector and shorted the connector. The short caused more than just this problem but for this narrative we will restrict to the slam/switch matrix problem.

Reading in other materials I recognized the problem as the slam switch issue. I used a logic probe to test other components and found the CPU board working, mostly as it should except for acting like the machine was slam tilted. There was little written about the problem outside of the slam switch. I decided to check the matrix by doing a diode check on all of the diodes in the switch matrix. When I did this, I found that many of the diodes were testing bad. These were being tested with the board removed from the machine.

Having replacement diodes in my parts drawer I decided that these must have gone bad during the short. I began unsoldering a few of the diodes. Once disconnected from the circuit board I remeasured the removed diodes and found the correct values on my meter, they were not bad. I then noticed that the bad diodes were all in the same row on the switch matrix. They all traced back to the Z15 chip. I replaced the Z15 7432 and the problem was resolved. --Kencaine 01:43, 24 April 2011 (BST)