Mortal Kombat 2 Arcade PCB Repair (Corrupted Graphics)

Описание: This was sent to me by a friend who needed help and asked if I could take a look. The palette and pixel data was corrupt. The schematic in the manual pointed where to go. There are basically 6 chips that handle the palette and pixel data. UA8, UC8, UB9, UB10, UA9, UA10. Knowing this, I broke out the logic probe and began looking at the data lines on the chips. I had a board in the past with almost this exact same issue and the UB9 chip ended up being bad. That chip tested good on this board, so that wasn't the cause. Testing on, I found that the SD04 data line on UB10 was dead. No activity at all when it should have been pulsing. This could either be caused by UB10 itself being internally bad, or an open trace between it and the corresponding input at RAM chip UB11. Rang the trace for continuity and it was in fact OPEN. Installed a small bodge wire to reconnect the connection and...it's fixed! The memory expansion board had a bad U13 rom as well. Replaced it with one from a donor board and the board is back to 100%. Cleaned everything up and it's working perfectly now. Just wanted to share for those who might run into something like this in the future. Thanks.