Gameplan Repair

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

GamePlan made pinball machines from 1978-1985. Their first pinball machines were cocktail size. The first full-size pinball machine was SharpShooter designed in 1979 by Roger Sharpe. The last pinball machine produced by GamePlan was called the Loch Ness Monster and only one was produced. The machine still does exist today in a private collection. GamePlan also made one widebody pinball machine called Global Warfare, which was designed by Roger Sharpe as well. The artwork was created by John Trudeau. Only ten Global Warfare machines were produced. Roger didn't realize that this design had ever been put into production until being presented with one during pinball expo.

2 Games

Title	Date of Release	Model #	Notes
Rio	1978		Cocktail
Black Velvet	05-1978		Cocktail
Camel Lights	05-1978		Cocktail
Foxy Lady	05-1978		Cocktail
Real	05-1978		Cocktail
Chuck-A-Luck	05-1978		Cocktail; factory conversion of Real
Family Fun!	04-1979		Cocktail
Star Trip	04-1979		Cocktail
Sharpshooter	05-1979
Vegas	08-1979		Cocktail
Old Coney Island	12-1979
Challenger I	1980
Super Nova	1980
Pinball Lizard	06-1980
Kings Of The Road	1981*		Never Produced
Global Warfare	06-1981*		Widebody; 10 pilot games were built, never released
Mike Bossy The Scoring Machine	01-1982*		never released
Sharpshooter II	11-1983
Attila the Hun	04-1984
Agents 777	11-1984
Captain Hook	04-1985
Lady Sharpshooter	05-1985		Cocktail
Andromeda	09-1985
Cyclopes	11-1985
Loch Ness Monster	11-1985*		Prototype

3 Technical Info

GamePlan utilized the Z80 microprocessor as their CPU of choice for all of their games. The early cocktail pins used the MPU-1 board, and the full-size machines used the MPU-2 board. The only difference is the amount of RAM. GamePlan used individual driver boards for the solenoids (the SDU-1 board) and lamps (LDU-1 and LDU-2 boards). The displays on all GamePlan machines are LED displays and hold up quite well because of this. The sound system did change frequently, starting out with Chime units in the early cocktails, to solid state "hard-wired" sound boards, to sound boards that were designed using the Motorola 6802 processor (MSU-1, MSU-2).

3.1 Game Plan Boardset

3.1.4 MPU-2 Boardset with MSU-3 Sound Board

Game Plan Boardset from an Andromeda

3.1.7 LDU-1 Lamp Driver Board

Game Plan LDU-1 Lamp Driver Board

3.1.8 LDU-2 Lamp Driver Board

Game Plan LDU-2 Lamp Driver Board

3.1.16 MSU-3 Sound Board

Game Plan MSU-3 Sound Board from an Andromeda

3.1.17 LLU-3 Sound Board

Pinball Lizard only.

3.2 Switch Matrix

The Game Plan switch matrix, like that of early Bally/Stern pinball machines, is driven by the CPU board. In fact, it is a lot like the early Bally/Stern in that it is a 5 x 8 matrix consisting of a maximum of 40 switches. There is a total of 5 switch strobes (columns), (starting with 0, ending with 4), and 8 switch lines (rows), (starting with 0, ending with 7). While Bally adopted its numbering convention for the switches to start at 01 and increase by 1 in the same strobe, and continue consecutively to 40, Game Plan, which probably didn’t want to be seen as copying Bally as a newcomer to the market, added a “0” to the end of its switch numbers for its early games. Game Plan switch numbering begins with 010 at Strobe 0/Line 0 and increases by 10 in the same strobe, continuing consecutively to 400. The switch matrix in all Game Plan games is numbered like this up to and including Sharp Shooter II. Starting with Attila the Hun, Game Plan dropped this silliness and went back to two-digit switch numbers. It’s worth noting that Game Plan numbered its solenoids the same way with early games getting three digit identifiers ending in 0 and then starting with Attila the Hun switched to 2 digit identifiers. The PA Pinball table below refers to "Returns" while in Game Plan schematics these are referred to as "Lines".

Early Game Plan Switch Matrix w/Three Digit Identifiers

Armed with the information of how Game Plan numbered switches in the matrix and specific switch numbers from the manual, it is then possible to map the switches from any given game to the switch matrix. Below is an example of this using Sharpshooter/ Sharp Shooter II.

Sharpshooter/Sharp Shooter II switches mapped to the switch matrix

• Please note that while Sharpshooter and Sharp Shooter II use the same game ROMs at U12 and U13, Sharp Shooter II only uses a single rollover switch for the right loop whereas Sharpshooter uses five star rollovers for the right loop.

Like Bally/Stern, the Game Plan switch matrix is controlled through the onboard PIA – an Intel 8255 at U17. But where Bally/Stern employed two 6821 PIAs on the CPU board, one for the switches and lamps and the other for the solenoids and displays, Game Plan only has a single 8255 on the MPU which is responsible for switches, controlled lamps, solenoids and displays. The PIA ports in early Ballys were wired directly to the switch matrix but because of the single PIA on the Game Plan MPU, the strobes which are run from the upper four bits of Port A of the 8255 (column drives) go from the PIA through the on-board 74154 4-16 line decoder at U14 and then out to the switches. The switch strobes are also shared with the display clock lines so its possible to have a machine where switches and displays are both having problems at the same time. A similar trick was later employed by Gottlieb in their System 3 machines where the switch and lamp strobes are shared. The use of the single 8255 and a 74154 may have saved Game Plan money compared to Bally which used two 6821 PIAs.

3.2.1 Architectural Difference From the Bally Switch Matrix

An interesting architectural difference of the Game Plan switch matrix from Bally is that the switch returns run through LM339 voltage comparators at U18 and U23 before going back to the 8255 on Port B. This is not something that was seen until WPC machines nearly a decade later. Using the voltage comparator allowed for simply reading voltage differential between the open and closed switch and outputting a logic low or high for the PIA, making for a more robust and reliable switch matrix.

All the switch columns and rows are connected at J5 of the MPU. However, some of the columns (Strobe 0 and 3) and most of the rows (Lines 1-2, 4-7) are also connected to J6 of the MPU as well. The reason for this is that J5 is normally connected to the playfield whereas J6 is the connector that goes to the cabinet. You can therefore tell where the cabinet switches for the matrix may lie. As an example, switches 09/090 – 16/160 are always found on the playfield.

The first switch (01/010) in the switch matrix is always found on the MPU board itself. The red switch at the top left of the board is wired directly to the switch matrix at Strobe 0/Line 0 and is referred to as the “Accounting Reset” switch.

However, while the Accounting Reset switch on the MPU board is wired into the switch matrix, the DIP switches on the board are not part of the switch matrix. Each bank is wired into one of four decoder lines from the 74154 that are dedicated to the DIP switches, although the returns for these DIP switches are wired into the switch return lines. The DIP switches are read only at power-up and once the board is booted the DIP switches are not scanned by the game program. Ideally, you are best to change the DIP switches on the board with the machine off, this way the change will be read the next time the machine is turned on. Another area where Game Plan switch matrix differed from Bally is that the “Diagnostic & Accounting” switch for Game Plan is actually part of the switch matrix and is always located at Strobe 3/Line 1 which is switch # 26/260. Bally smartly kept its diagnostic switch out of the switch matrix with it wired directly to a single pin on the U10 PIA and returns to ground on the SDB. If you are able to successfully enter accounting and diagnostic mode on a Game Plan machine, that confirms at least the switch’s associated strobe and return lines are working correctly. The Diagnostic and Accounting switch may briefly show on the displays when first entering the switch test but another press of the button after that should advance you back to attract mode.

The following table shows which switch lines and DIP switch numbers go to which LM339 on the CPU board. A failure of an entire switch row and the associated DIP switches could be a result of a failure of its associated LM339.

LM339s and Associated Switch Lines/DIP Switches
U23	U18
Line 0 (Sw 1, 9, 17, 25)	Line 1 (Sw 2, 10, 18, 26)
Line 5 (Sw 6, 14, 22, 30)	Line 2 (Sw 3, 11, 19, 27)
Line 6 (Sw 7, 15, 23, 31)	Line 3 (Sw 4, 12, 20, 28)
Line 7 (Sw 8, 16, 24, 32)	Line 4 (Sw 5, 13, 21, 29)

3.2.2 Off-Board Switch Isolation/Speed

All switches in the switch matrix have a 1N4004 isolation diode on them to allow for each switch to be properly read in the matrix. A failure of one of these diodes will likely cause a problem with the switches in that particular row. In one game, Lady Sharpshooter, to improve switch responsiveness, Game Plan also added .1uf capacitors across certain playfield switches, borrowing yet another trick from the Bally playbook. You can find these for example on the pop bumper switches in LS. It is unclear as to why Game Plan did this in only LS but given the high gain and fast response of the LM339s on the switch returns, there was likely little to be had with the addition of the switch capacitors.

3.2.3 MPU-2 Only - Error In Early Parts Manuals For Switch Matrix Resistors

Early parts manuals have an error for the eight pull-up resistors on the outputs of the LM339s/switch return lines that go to the PIA. In the parts manual these resistors are identified as #6 in the parts table as 100 ohm/ 1/4w resistors. These in fact should be 10k ohm/ 1/4w resistors. While the parts catalog is incorrect, all schematic renderings of the MPU-2 are correct. Installing 100 ohm resistors will render the switch matrix inoperable and short the entire switch matrix to the 5v rail.

The parts catalog was updated in later machines and if you look in the Lady Sharpshooter parts catalog, you will see these resistors identified as #61 in the parts table (they just added a "1" on the diagram) and are properly labeled as 10k ohm/ 1/4w resistors.

This errata only applies to the MPU-2. The MPU-1 parts catalog lists these resistors correctly as 10K ohm resistors.

4 Problems and Solutions

With GamePlan using individual boards for everything, interconnects tend to be a culprit for many problems. Before you do anything, you should first unplug all boards, and check the voltages on the power supply.

4.1 Power Problems

First and foremost, replace the big capacitor! This fix a lot of issues with GamePlan pins. The actual capacitor value in this PSU-1 power supply varies, as some machines were shipped with the 25v 11,000 capacitor (typically the silver color) and some were shipped with a 15,000 25v capacitor (typically a blue color). Make note of the polarization of the capacitor, cut off the screw mounts (or desolder them), and replace the capacitor with either another screw mount or through-hole design. If through-hole, just use some hookup wire to jumper the capacitor to the circuit board.

4.2 MPU ROMs

4.2.1 Modifying the MPU-2 Board for 2716s

Early MPU-2 boards came from the factory configured for 2316-type masked PROMs. With any sort of corrosion or tarnishing of the pins, these ROMs could very likely be damaged and unusable. Below are a pair of original ROMs from an Old Coney Island - notice the tarnishing on the pins.

Original OCI! PROMs

The easiest thing to do is get a new set of standard 2716 ROMs. The good thing about the MPU-2 board is that it is designed to accommodate 2316s, TMS2716s, standard 2716s, 2532s or 2332s with a few simple board modifications. With a little more work the board can also handle 2732s (more on this later). MPU-1 boards can also be cut and strapped for 2716s but the procedure to do so is different than what's outlined below. Standard 2716s are best since they are easily available, and most EPROM programmers can handle them.

To set the board to use 2716s simply requires cutting two traces and installing two jumpers. This process breaks the ground connection to pin 21 of the ROMs bringing 5v instead and drives the logic level correctly for reading 2716s. Trying to interpret the schematics for what to do here is a challenge, to say the least but it is easy to do if you can see what needs to be done. Three steps are done on the component side of the board (steps 1, 2 & 4 below) and one step is done on the solder side (step 3.) Here’s the photo guide to how to do it.

Step 1

Step 1 - First thing you need to do is cut a trace on the component side of the board. There is a via which is between pins 35 and 36 of the Z80 that then connects to pin 21 of the ROMs. You’ll know this is connected because you can test for continuity between test point 7 (ground) and pin 21 on any of the three ROM sockets. Cut the trace carefully next to the via with a Xacto knife, insuring you don’t damage the traces on either side of the via. If you don’t want to cut the trace you can remove the solder from the hole and drill it out with a tiny drill – you just need to break the connection from one side of the board to the other. You’ll know you’ve successfully cut the trace by testing for continuity between TP7 and pin 21 on any of the three ROMs – there shouldn’t be any.

Step 2

Step 2 – Next, on the component side, install a jumper between the two pads below U26. This brings 5v to pin 21 which is required to read the 2716s. Using a cut off lead from a resistor is the easiest way to make this jump. Remove solder from the holes, install the cut off lead, solder it in place and trim. You’ll know this is working because you should now have continuity between TP1 and pin 21 on any of the ROMs.

Step 3

Step 3 – Now, on the solder side of the board cut the trace that goes to pin 8 on U24. You’ll see a mark on the board that indicates what to cut. When you’re done, there should be no continuity between pin 8 on U24 and pin 18 of U13.

Step 4

Step 4 – Now back on the component side of the board install another jumper between the two pads above U24 as shown – this is the bypass for U24 to provide the correct logic level at pin 18 of U13. You’ll know this is working if you have continuity between pin 8 at U25 and pin 18 of U13.








That’s it. The board is now ready to take standard 2716s which you can simply pop into the sockets and they will be used by the machine.

4.2.2 ROM Sizes, Cutting, Strapping, Compatibility Issues

Starting around the time of Attila the Hun, Game Plan switched to using 2732 EPROMs instead of 2716 EPROMs or masked ROMs, likely because of cost and availability/flexibility. From AtH to Andromeda, all Game Plan machines used a 2732 ROM in U13 and a 2716 ROM in U26 with a few exceptions. Then with Cyclopes, all three ROM sockets were populated with 2732s, the only Game Plan machine configured as such.

Typical Late Game Plan ROM Config

The exceptions to the above are AtH, Lady Sharpshooter and Andromeda. For AtH and LS, there are ROM images out there that use either three 2716s or one 2732 and one 2716. If you took the AtH version with the three 2716s and combined the U12 and U13 images into one, you get the 2732 AtH image. Try the same thing with the Lady Sharpshooter images however and it winds up the images don't match.

For Andromeda, there are ROM images out there that use either a 2732 at U13 and a 2716 at U26 or two 2732s. The 2732 image for U26 is different than the 2716 U26 image (it’s not just the same image padded with extra blank space). A quick check does not reveal a difference in gameplay between the two versions. Seeing this, you would think that it would be safe to combine the U12 and U13 images for any game prior to AtH and cut/jump the board to use a 2732. Unfortunately this is not the case. While you can do this and may get the MPU board to boot, the fact is that the machine may not work correctly. Switches and solenoids may be misregistered so you can have problems like the wrong sound playing, the wrong solenoid firing or switch hits not being recognized. The reality is this:

If a machine was originally configured to use 2716s (machines before Attila the Hun), it is best to use 2716s and should not be changed to use a 2732 by combining the ROM files.

If a machine was originally configured to use 2732s (machines from Attila the Hun to Andromeda), it is best to use a 2732 and should not be changed to use two 2716s by splitting the ROM file.

The reason why it is important to note this is that if you are using a board that was originally in say a Sharpshooter and want to use it in Andromeda, you must cut and jump the board for 2732 use. Alternatively, if you have a board that was in an AtH which was using a 2732 and want to use it in an OCI!, you have to undo the 2732 cuts/jumps to allow it to use 2716 EPROMs. In the previous section, Modifying the MPU-2 Board for 2716s, are the details on how to convert a board that used masked ROMs to use 2716 EPROMs. These modifications are also necessary if you want to use a board with 2732s as well. If you are looking to convert a board that used masked ROMs to 2732s, then start there. Also, if you have a board that uses 2732s and want to use it in a machine that uses 2716s, then this is where you need to wind up after converting. The procedure outlined below to go to or from 2716 <-> 2732 EPROMs are for machines from Attila the Hun through Andromeda with a ROM version that uses the 2716 at U26. This procedure does not cover what needs to be done to a board for Andromeda with two 2732s or Cyclopes as those are different.








For AtH through Andromeda, there are four additional steps required with cuts or jumps to the board in addition to the previously mentioned 2716 cuts/jumps.

Step 1 – Cut/jump the trace to pin 21 on U26

Step 1: Cut the trace to pin 21 under U26

From 2716 to 2732: Cut the trace to pin 21 that goes from U13 to U26. Normally this trace was cut under the socket at U26 as shown in the photo. You can try cutting this trace next to the socket but you must be sure to not cut the adjacent traces. The trace under the socket has more room and more margin for error.

Step 1: Install a jumper wire from pin 21 on U13 to pin 21 on U26

From 2732 to 2716: Install a jumper wire from pin 21 on U13 to pin 21 on U26 as shown in the photo. This reestablishes the connection that was cut at the factory.










Step 2 – Jump/remove the wire from pin 21, U12 to pin 13, U25

From 2716 to 2732: Install a jumper wire from U12, pin 21 to the pad shown in the photo below. If you trace this down on the board, you’ll see it goes to pin 13 on U25.

Step 2: Jumper/Remove wire to pin 21 under U23

From 2732 to 2716: The grey wire you see in the photo above was installed at the factory. Remove this wire to use 2716s.


Step 3 – Cut/jump the trace from U4, pin 12 to U25, pin 13

Step 3: Cut the trace from U4 pin 12 to U25 pin 13

From 2716 to 2732: Notice the cut mark on the board between U24 and U25. By cutting this trace here you will sever the connection from U4, pin 12 to U25, pin 13.

Step 3: Use the holes marked to jump U4 pin 12 to U25 pin 13

From 2732 to 2716: You can easily reestablish the connection from U4, pin 12 to U25, pin 13 by using the jumper holes on the board. By soldering a jumper wire to the holes as shown, you will be connecting the two aforementioned pins.







Step 4 – Ground/remove ground to U4 pin 12

From 2716 to 2732: Scrape off the solder mask above the jumper hole and use a short piece of wire lead cut off from a resistor and solder these two together.

Step 4: Jump/Remove from the pad between U4/U24 to the ground trace

From 2732 to 2716: As shown in the photo above this jump was also performed at the factory. Remove it and any solder insuring that there is no continuity between the pad and the ground trace (should look like the photo with the jumper wire in step 3 above).

Jump pin 12 of U22 to pin 9 of connector J4 to support 7 digit displays

It is worth noting here that there is one other jump which needs to be performed if you’re taking a board from a game with 6 digit scoring and installing it in one with 7 digit scoring – pin 12 of U22 to pin 9 of connector J4. You see in the adjacent photo, this jumper from the connector to the nearby pad completes this jump. This is another factory installed jumper wire. While this isn't directly related to the ROM, it is a requirement to support the 7 digit displays.

4.2.3 Substituting a 2764 EPROM for all the ROMs

John Robertson has published a technique for substituting all the ROMs in a machine with a single 2764 EPROM at John Robertson's Game Plan tips. It does leave pins sitting outside of the socket and would likely not work for Cyclopes (not enough space).

4.3 MPU boot issues

4.3.1 MPU LED Flash Codes

Game Plan was like Bally in that it has a diagnostic LED that flashes as the machine boots. If you get to six flashes then the board has fully booted and the MPU is functioning properly. If you get less than 6 flashes it indicates a problem with the board. Oftentimes you won’t get any flashes. This could be a power problem. It could also be a problem with a damaged reset circuit due to a leaking battery. It could also be a problem with one of the socketed components on the board. The following is adapted from the Game Plan MPU troubleshooting flowchart.

If the reset, CPU, PIA and voltages are all good, you should get at least one flash. If it stops after one flash, swap out the Z80 CTC (U10.)

If you get two flashes, either one or both U6 and U7 RAM are bad. These are difficult and expensive to come by. As of December 2015, Arcade Chips still has 6551s but they are $10 each in quantities less than 5.

If you get three flashes, the 6810 at U8 is bad. It is possible that you may have a MPU-1 board without a 6810 – that’s ok. You’ll still get a flash as if you have a good 6810.

If you get four flashes and it stops, that says that part of the PIA is bad. This is an unusual situation because the LED will not flash at all with a bad PIA. If you haven’t replaced the PIA at this point now is the time. But if you replaced the PIA in the first place with a known good one, then the 74LS00 at U4 is likely bad.

Finally if you get to five flashes and it stops, the board has gone through all its internal tests and is trying to boot from the ROMs – unsuccessfully. At this point you know the ROM(s) are bad and need to be replaced.

When you get the sixth flash you know the ROMs are good, the board is running the game code and the board is fully booted (though you still may have a problem with the switch matrix, solenoid lines or displays.)

If you replace any of the above socketed components with new ones and still have the same problem, you have to suspect a bad socket and/or corrosion which may be preventing the board from communicating with that part. Or possibly one of the other soldered in logic chips on the board. The only solution is to find, remove, and replace the offending component.

4.3.2 Watchdog Timer – Game Plan’s Version of “Blanking”

If the LED on the MPU board in your machine is continually blinking like in this linked video: http://youtu.be/wbu2jCTcxyI it shows that the board is in a state of constant reset. For the Game Plan MPU, this is a classic case of a problem with its watchdog timer circuit.

What is a watchdog timer (WDT)? A basic description can be found here: http://en.wikipedia.org/wiki/Watchdog_timer

In the case of the GP MPU, if the system isn’t running correctly for some reason, there are specific components that are designed to reset the MPU. The functioning of these components makes them analogous to the blanking circuit on Williams system 3-11 machines.

The problem with diagnosing this sort of error is that it’s difficult to determine where the fault is. Is the problem that the system is not running correctly, so the watchdog is resetting the board? Or has something in the watchdog circuit failed which puts the system in continual reset?

Assuming you have correctly mitigated any battery corrosion on the board and have not damaged any IC connections, to solve this problem, the first and easiest thing to do is to shotgun all the socketed LSI (Large Scale Integrated) components on the board (Z80, Z80CTC, 8255 PIA, ROMs, 6551 RAMs and 6810 RAM if applicable).

This helps you to narrow down where the error may be on the board by insuring that all the LSI components are working correctly. You may also choose to shotgun any other socketed components on the board. The reason is twofold: first, it is already socketed so that makes it easy to check and swap in a known working component. Second, for some components like U14, U1, U2, U3 and U5 all play a part in the watchdog/reset circuit. If one of these components is bad or is not making a good connection to the board because of bad prior work, it could be responsible for the constant resetting.

Of all the aforementioned components, the most likely one to fail after the PIA is U14. If this is still soldered to the board (this is how it comes from the factory) you can easily check it with a multimeter. The procedure for this is outlined in the General section of PinWIKI: General#Testing_an_integrated_circuit.

You should get a reading of .4-.6 on all pins EXCEPT 18-19 (should be 0) and 24 (should be around .2-.3).

If after shotgunning the components and testing U14 you still have the continual reset, the next thing to do is see if the board will boot without the WDT circuit. The easiest way to do this is to short pins 25 and 26 of the z80 CPU chip (U11) together with a small screwdriver. This puts 5v directly on the reset line and if the board boots, you know the problem is somewhere in the WDT circuit. (see photo TBA.)

NO FLASH, SOME FLASHES, SIX FLASHES

When you short pins 25 and 26 on the CPU chip together, one of three possible things may happen.

1 – You get 6 flashes on the LED and the light goes out. This tells you that all is good with all the major components in the board and something is not right with the WDT circuit itself which is continually resetting the machine. You might be tempted to permanently short these two pins together to get the game to play but don’t. The WDT is also part of the power up reset circuit which insures that all the power stabilizes to the board before it attempts to boot. Shorting these pins together bypasses that part of the circuit and will not allow the machine to boot properly when you turn the power switch on the machine.

2 – You get less than 6 flashes and the light goes out. It is possible that when you short pins 25 and 26 together you can get less than 6 flashes. If you didn’t shotgun the major components, one or more of the LSI may have failed and with the machine in continual reset, the failed component is hidden. Depending upon how many flashes you get you may need to replace other components per section 4.3.1 – MPU LED Flash Codes. Because something else is failed and the board isn’t fully booting, the WDT continues to reset the board to insure no damage is done and attempt to restart things so the board boots. The chances are once you fix the component indicated by the number of flashes the board will boot correctly and the continual flashing will stop.

3 – The LED locks on. This is a special case of point 2 above. One of the major components has failed and it is not even allowing the board to put out even one flash. In this particular scenario, one of the first components I would swap out would be the two 6551 SRAMs and see if boots. If it does, then swap back in one SRAM at a time to see which one is bad.

One of the three things mentioned above will happen because even before shorting the CPU pins together, a flashing LED indicates that some parts of the board are running. After all, the LED is controlled by the PIA which is controlled by the CPU so there is some life on the board. Regardless, you’ll know you have a problem because when you remove the short between pins 25 and 26, the LED goes back to flashing constantly again.

SO I KNOW THE WDT CIRCUIT HAS A PROBLEM – HOW DO I FIX IT?

For points 2 and 3 above, you have suggested courses of action. But if the board fully boots with the CPU pins shorted, you know you have a problem with the WDT circuit. Fixing this requires understanding the parts of the circuit and the flow. The most important part is realizing that the GP WDT relies on the 8255 PIA. The assumption is that if the system is running correctly, the WDT is looking for regular signals on the PIA, which is interfaced one way or another to the displays, lamps, switches and solenoids – basically the whole machine. Since you shotgunned the 8255 earlier (you did shotgun the PIA, right?) you know this chip isn’t the problem, and can go from here.

The next place the signal necessary to trip the WDT circuit goes from the PIA is to the 74154 at U14. Since you checked this with a meter earlier or shotgunned it, assume this is not the problem.

Next, the output of pin 11 on U14 sends a periodic signal to the one shot multivibrator (74LS123) at U1. Here, another timing signal that comes from the CA339 at U2 is combined and checked. If the signal from U14 does not get to U1 in time, the signal from U2 goes through and sets the 5v low to the reset pin on the MPU. The timing of the signals for U1 and U2 is set by the three tantalum caps (usually blue) around these components. If you look at the GP schematic and parts manual, you’ll see that all three caps here are listed as 1uf yet the chances are that your board has two 10uf caps and one 1uf cap. It is a safe assumption that the GP engineers found that with all 1uf caps here the machine was more prone to unintentional resets and decided instead to put 10uf caps instead which put more tolerance into the WDT circuit. These 10uf caps are specifically located across pins 6&7 and 14&15 on U1.

At this point, if the machine is continually resetting you are down to either a problem with U1, or the three tantalum caps. You can test U1 using the same IC test procedure outlined earlier. You should get a reading of .4-.6 on all pins EXCEPT pins 3, 11 and 16 (.3) and 6, 9 and 14 (should be 0). If U1 shows a fault, you have found the location of your WDT problem. However, if U1 checks out, that leaves the caps. If you have an ESR meter you can check the caps. If not, you can shotgun the three caps here – they are cheap and easy to replace.

NOTE: Replace the caps with the SAME values that are on the board and NOT the values that are in the schematic or parts manual. Game Plan never updated its manuals or schematics with this information and in fact was notorious for not updating documentation with changes of this type. If you go with the parts listed in the manual you will be shortening the time on the WDT circuit and run the risk of inadvertent resets. Also, it is recommended to use tantalum caps as aluminum electrolytics in the smaller sizes are more prone to drying out and changing value over time which could lead to inadvertent resets (though if that's all you have you can go with the electrolytics but it would be best to ultimately replace them with tantalums when you make your next parts order).

Lastly, be sure to note the polarity of the caps when you remove them and be sure to install the new ones with the same polarity otherwise fireworks might ensue.

After U1, the signal goes through an OR gate at U5 where it is combined with a signal from the hex inverter at U3. The signal at the hex inverter is controlled by the 10uf 16v electrolytic cap at the bottom of the board. It is rare that this cap measures bad but there is no harm in replacing it. You can also check U3 and U5 with your multimeter using the same IC test procedure outlined above. After this, there are four transistors labeled A, B, C & D on the board. A, B and C are 2n3904s and D is a 2n4403. These can all be tested using the transistor test procedure outlined on Pinwiki. If you have a MPU v1 board with the daughterboard or a v2 board, there will be two additional 2n3904 transistors that you will need to check.

You could also be having a problem with the 8.2v Zener on the board or the other resistors in the area of corrosion around this part of the board. Unfortunately, the only thing you can do is remove the corroded components, mitigate the corrosion, and replace the components with all new ones. NOTE: Always replace components on the board with the same value components you removed and not what the parts manual says. Yes, it bears repeating. As stated earlier, Game Plan did not update its documentation to reflect engineering changes so always replace like for like.

I CHECKED ALL THESE OUT AND THE DAMN THING IS STILL RESETTING! WHAT THE HELL?!?!

If you check all the above and everything looks good but the board is still continually resetting, you have to throw normal logic out the window and start looking at the prior work done. Start at the PIA socket. Is the socket clean? Do you have continuity from the legs on the chip to each corresponding pad on the solder side of the board?

If that all looks good, next you have to check the connection between the PIA and U14, especially if the latter has had any prior work done to it. U14 is a 74154 that is a 4 to 16 line decoder. This means that four lines go into it from the PIA, and the four signals are combined to determine which of the 16 output pins are triggered. For this part to operate correctly, all four lines have to have continuity from the PIA to the decoder. Specifically, the lines go:

PIA Pin #  74154 Pin # 37  20 38  21 39  22 40  23

You should check for continuity from the leg of each pin on the PIA to the leg of each corresponding pin on U14. If any are bad, they need to be corrected. While these four pins are connected by traces on the component side of the board, if the through holes for the chip pins are damaged when the component is replaced, you can lose continuity.

Next, from the 74154 check for continuity from pin 11 to pin 10 at the 74123 at U1. Again if there’s no continuity between these two pins, the board will be in constant reset.

There are two ways to correct continuity problems between any two points on the board. You can either run a jumper wire on the solder side of the board between the two affected pins or you can repair previous work that damaged a through hole with an eyelet, and then install a new socket. Sometimes you may need to do both if the damage is extensive, which is possible for the Game Plan MPU board if someone who is inexperienced worked on it.

4.3.4 Repairing Alkaline Corrosion

The #1 problem found on gameplan machines is the 3.6v NiCad battery mounted to the MPU board exploding, causing acid damage to the traces around. Early GamePlan pinball machines (SharpShooter, ConeyIsland, SuperNova) mounted the board vertically which the battery fluid would damage mostly the reset circuitry. For the rest of the games that have the board mounted horizontally (Attila, 777, Lizard, Global Warfare, Cyclopes, etc.), the damage tends to be worse, as the traces and sockets for the roms, cpu, and ctc are damaged. If you have an acid damaged board, it is possible to recover it, but it takes lots of time and patience. The best place to check out the procedure is John Robertson's page Battery Leakage Repair

4.3.6 Using a PC Power Supply For Bench Testing

There is no practical way to use a PC power supply for bench testing the Game Plan MPU board. The reason is to get the MPU to fully boot, you need +5v for the logic, +12v for the reset circuit and +24v for the zero crossing circuit. Standard PC power supplies do not have all three of these voltages. And while Clay has published a method to get more flashes on his website: Powering the MPU board on the bench I have had inconsistent results with this method at best.

The foolproof solution is to use a Game Plan power supply out of a machine with only J1 connected to the MPU board. Connected in this fashion you should get all six flashes out of a properly working MPU board.

4.3.7 Other MPU Repair Guides

• MPU2 Repair guide on Pinside.com
• Repair tips on flippers.com

5 Parts Substitutions & Replacements

Since there aren't really any sources for spare Gameplan parts other than other Gameplan machines, broken or worn out parts typically have to be substituted using mainly commonly available classic Bally and Gottlieb parts.

5.1 Aftermarket Replacement Boards

5.1.1 MPU

Aftermarket replacement MPU boards can be obtained from here:

Jim Francesangeli
Echo Lake Pinball Service & Sales
925 Marwin Dr.
Hinckley, Ohio 44233
Tel: 330-278-2228

Boards are built in batches and not always available on-demand, so you may have to request to be added to a wait list before another batch of boards is built

Gameplan replacement MPU2 board

Gameplan replacement MPU2 board information sheet

5.2 Shooter Assembly

5.2.1 Housing

The beehive housing part # 4A-115-W is a direct replacement for the beehive housing found on Gameplan games. This can be obtained from marcospecialties.com, pinballlife.com, or pbresource.com

5.4 Slingshots

Slingshot arms tend to be a commonly broken part on gameplan games.

One close possible substitute is The Williams System 11 A-7986 slingshot arm, according to this Pinside thread. (Sources: Marco Specialities)

5.5 Drop Targets

There are two general approaches to substituting broken Gameplan drop targets, and each method has its advantages and disadvantages. One uses Gottlieb drop targets, the other uses Data East drop targets

Drop target size comparison

5.5.1 Gottlieb Drop Target Substitution

Gottlieb Drop targets can be used as a near match for Gameplan drop targets, however, they will need to be modified. The slot in the center of the target will need to be lengthened. This is to ensure that the lift arm doesn't jam when the target is raised or dropped. This slot can be enlarged with a Dremel tool. Stack 2-3 blades to match the width of the slot, then lengthen the hole as necessary.

Additionally, a strip of foam or beer seal may be necessary on the reset bar in order to fully reset/raise the Gottlieb target. However, be mindful about not raising the target too high so as to avoid breaking off the foot of the target when it gets reset by the solenoid.

Gameplan & Gottlieb drop target feet comparison

This approach can potentially weaken the drop target and make it more prone to breakage. However, Gottlieb targets are a close enough size match that they can be used side-by-side with Gameplan targets (after the slot modification). Additionally, Gottlieb targets can be obtained in similar colors.

5.5.2 Data East Drop Target Substitution

1/4" spacers (or stacks of washers totaling 1/4" in height) will need to be added between the drop target cage and the bottom of the playfield. Additionally, wood screws that are 1/4" longer are also recommended to accommodate the spacers.

Data East drop targets only come in white, and cannot be color matched to the original Gameplan drop targets (however, there is a technique to dye plastic parts that might work). Also, because of the height change required to accommodate these drop targets, and the larger face size of the targets, the Data East drop targets can not be mixed and matched with original Gameplan drop targets.

Gameplan and Data East drop target face comparison

Despite these drawbacks, this is the easier substitution approach since it doesn't require the modification of the drop targets themselves, unlike with Gottlieb drop targets.

5.6 Drop Target Cage

If most or all of the Gameplan drop targets are unusable, instead of substituting individual targets, it is sometimes possible to replace the entire Gameplan drop target cage with a Gottlieb drop target cage that has the appropriate number of spaces for targets.

5.7 Flipper Assembly

Some flipper assembly parts can be substituted. However, there have also been unverified discussions about retrofitting WPC flipper assemblies to replace the original Gameplan assemblies, as well as substituting new classic Stern assemblies with a GamePlan coil.

5.7.1 Flippers

The plastic flippers can be substituted with a white Bally pre-1987 flipper & shaft. Part number: A-3994-5. This can be found on marcospecialities.com, pbresource.com, and likely with a few other vendors.

5.7.2 Bushing

A direct replacement is carried by marcospecialities.com as part number: 03-40001A.

5.7.3 Link

No direct substitution currently available, however, PBResource offers lengths of link material for making custom links, which can be cut and drilled as needed: PBResource MAT-LINK

5.7.4 Coil Stop

Coil stops on all Game Plan machines are shared between all mechanisms with the exception of the drop target coils.

The flippers, power (jet) bumpers, slings, ball kick out and ball kicker all use part # 10-00009A "plunger stop bracket". If you have access to a parted machine and need new flipper stops, oftentimes the ones from the slings have little wear on them and can be used as a replacement.

A possible substitution might be Gottlieb part GTB-A5189+ from PBResource.com, but this is currently unverified.

5.7.5 EOS Switch

A Williams 03-7811 might be a possible EOS replacement replacement, but this is currently unverified.

5.8 Solenoids/Coils

All coils are 24VDC. Most Gameplan coils are available from PBResource.com

• 21-50001B used for single drop target and pop bumpers (a Gottlieb A-5194 is a close substitute). This coil uses sleeve # 03-40008N (same as Williams # 03-7066-2).

• 21-50002B used for flippers (a Gottlieb A-17875 should work as a substitute). This coil uses sleeve # 03-40008N (same as Williams # 03-7066-2).

• 21-50003B used for knocker and slingshot kickers (a Gottlieb A-19300 is a close substitute). This coil uses sleeve # 03-40008N (same as Williams # 03-7066-2) when used for slingshots. When used for knockers use sleeve # 03-40012N (same as Williams # 03-7066-4).

• 21-50004B used for chimes (a Gottlieb A-26450 is a close substitute). This coil uses sleeve # 03-40027N (same as Williams # 03-7067).

• 21-50005B used for ball return outhole (a Gottlieb A-16570 is a close substitute). This coil uses sleeve # 03-40008N (same as Williams # 03-7066-2).

• 21-50006B used for ball return outhole (a Gottlieb A-17876 is a close substitute). This coil uses sleeve # 03-40008N (same as Williams # 03-7066-2).

• 21-50007B used for large drop target bank reset (no substitutes available). This coil uses sleeve # 03-40038A (no substitutes available).

• 21-50008B used for flippers (a Gottlieb A-24161 should work as a substitute). This coil uses sleeve # 03-40008N (same as Williams # 03-7066-2).

• 21-50009B used for large drop target bank reset (no substitutes available). This coil uses sleeve # 03-40038A (no substitutes available).

6 Repair Logs

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