Please post a picture of the MPU board.

If you didn't have a compromised board, I'd suggest getting a new Eprom, and/or a new Ram (preferably a NVRAM) chip.

I'd suggest a replacement ribbon cable (or at least re-seat the ribbon cable) to the display, and to maybe refresh the solder connections to the display ribbon cable.

I'd suggest that the display going black is VERY commonly the three pin plug on the display driver board. Replace both the pins and the plug with trifurcon for the red and black power in.

I'd suggest that lately I've had a lot of machines this age that I've had intermittent power problems, and I've had to replace the pins at the top of the power driver board, and the connector there with trifurcon. (This for me has mostly been about intermittent opto boards, but bad power can cause ANY problem you can imagine).

With the board having been acid (alkaline) compromised... well, it seems your board is still compromised. Maybe an address line that only gets used when it accesses a higher memory location in ram or rom, but something still isn't right.

It seems to be accessing the wrong section of programming for what it's doing.

(I was just thinking... this would be an ideal amusement auction piece... disable the coin switches, lock the door, make it coin play only, show it with the attract mode working perfectly, lock the backglass so that no one can see the acid (alkaline damage)... buyer beware!)

It really sounds like your cpu is not running the correct section of code, or is accessing the wrong inputs/outputs when it's running it's code.

Of course, trace your CN6 pin 10 (Test button enter) and pins 9, and 8 for your service switches. Maybe ground them directly by pulling CN6 and using an alligator clip. Just in case you've got a switch or wiring problem.

I used to be more involved in repairing battery acid (alkaline) damage, but almost everything I went to heroic lengths to repair ended up being troublesome a couple of years later. This was probably because of inadequate alkaline remediation techniques, but it has left a sour taste in my mouth about battery acid (alkaline) problems.

Some things are just worth the $449 replacement board, and that's where I've been going lately, instead of digging as deep as you are likely going to have to do with this project. I apologize in advance if I'm not as much help to you as Chris Hibler, or the Coin Op Cauldron guys.

Good luck!

Ha! Thanks PinRetail

Another possibility is that the communication between the MPU and the DMD controller isn't working correctly.
The game "seems" be be in audits because the MPU sends a message to the DMD Controller, but the message is corrupted along the way, and the 74XX273 at U201 instead sends the "I'm in audits" command to the DMD controller.

Replace U201.
It can't be reliably diode tested.
You might get lucky testing it's outputs with a logic probe.
But I'd probably just change it.
--
Chris Hibler - CARGPB #31
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