Donkey Kong 2 board pcb problem

RedlandMan

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I just purchased a non working donkey Kong cab on ebay . It was doing all kind of crazy stuff in the cab so to rule out monitor and power supply i now have it laid out on my bench. All roms have been verified ,cleaned ,and reseated. I have not checked anything else at this point. Heres a pix of whats its doing just in case anyone has seen this problem and can at least point me to the board with the problem. Hopefully ill have time to work on it tommorow. Thanks,Luis
 

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the Z80 CPU is bad I think. if you have another Nintendo board that works, try pulling the CPU out and stick it in this board. don't ask me for specifics like locations or part numbers, I don't know these heh.
 
The DMA is soldered. If i had a working board i could isolate the problem to one of the boards which would make my life alot easier.
 
Yea my DMA was soldered too, try reflowing it? That's what I did to fix mine. I replaced the DMA then I got a screen like yours. Then I reflowed the solder and it fixed the problem.
 
Have you checked the adress and data lines to see if you have one thats stuck high or low. Id does look like its on the cpu board and not the video side if that helps
 
The D8257 chip controls the reset to the Z80 chip. It could be faulty but I have also experienced corrupted bad data on these boards at Eprom locations 5B and 3H on the CPU board even after it verified itself correct in winromident with the correct checksum. Reburned the chips and game booted up fine.
 
Its been about a year since i has any time to work on my games but a have a little time now and put this board back on my bench. The screen looks a litttle diferent than it did before. maybe for the worst.Ive put in a known working dma and z80. Ive also ruled out the roms as i tried it using the braze kit that bypasses them. The problem is in the cpu board as the video board is confirmed working with another cpu board. any help pointed me in the right direction would be apreciated
 
Aside from reseating/verifying ROMs the only other thing to do is toss it on the bench and use a Fluke to find out what the issue is. Could be datapath from ROM to CPU, address decoding issues, clock issue... too many variables. :(

Edit: Not entirely true.. you could start sniffing around those paths with a logic probe and look for floating/stuck pins.
 
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