(Topic ID: 254162)

Need help with Gameplan MPU-2 (switch issues and more)

By Chisel

4 years ago



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#4 4 years ago

Gameplan MPU's suck hardcore when it comes to repairing them. Tripley so if they have battery corrosion.

What game eproms are in the MPU's? Are they all Sharpshooter 2 roms or are you swapping the roms from a 4th known working board that came with the fully working game?

Gameplan heavily recycled the game software/rules from title to title but they aren't identical AFAIK.

Are the boards strapped correctly for the ROM sets you are using? Never found a good source that correctly identifies what to do and these boards are notoriously fickle that I was always afraid of messing with ROM jumpers on these turds.

Also FYI in case you don't know. The boot up sequence sounds like it works like the Bally boot sequence but it doesn't.
i.e the stuff needed for the game to get to the second flash includes the stuff tested at later flashes. So if the parts for flash #5 aren't working you won't get flash number 2. I think there is maybe one flash (the 6th IIRC) that you can get to that accurately states that that part is wrong. Otherwise you get no flashes or ALL flashes and pretty much nothing in between. Worthless.

Turn off the dip switches and run the switch tests with the pf switches disconnected from the board and use a jumper wire to test the switch columns and rows. I had a bally with switch issues once and it had a couple of bad diodes on the dip switch banks.

Good Luck
I fixed a shit ton of these about 10 years ago. Got around 10 out of 20 working. Kept 2 spares on a shelf. They didn't last a year sitting. Pulled them to use and both had died. Awful systems. The batteries usually manage to wipe out around 12-17 chips and their traces.

#7 4 years ago
Quoted from Chisel:

Have any documentation on the boot up sequence issues you mentioned?

I don't recall if Clay mentions this in his guide for Game Plan but have experienced it first hand a couple of times on the boards I was repairing. The boot up sequence they wrote needs some components right from the first flash that are then "tested" by later flashes. I only ever got less than full boot but more than 1 flash where the bad component matched the flash ONCE (think it was the 6651 RAM test). Several other times I had boards that got a single or no flash and it was the 3rd, or 5th or later component halting the boot prematurely (one time think it was the 6840 or 6540 or whatever that part next to the Z-80 is)

Bad Engineering. They wrote a test sequence that only in effect confirms a 100% working board, anything less than 100% and you aren't really testing anything.

You can confirm this on a good board. Simply see what makes the last flash and remove it and see if you get full minus one flashes. Put that part back in then take the second to last component out and see if you get full minus two flashes. etc. all the way down to the first flash. Please share your results. Then to really finish documenting this see what happens on any component that actually matches the flash by removing all the components from after that flash and see if it still reflects that part correctly. You can actually do this with a Bally board with the exception that one of the PIA's that is tested again later is needed to make the LED flash.

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