Another arcade PCB repair tonight. NBA Jam this time. Got this board on the cheap ($25) in the hopes that I could fix it. Indeed I did, but again, like most of these that I've worked on recently, it proved to be quite the task. Here's the run down...
Initial symptom - Dead. DOA. Nothing. Paper weight.
After giving the entire board a good, thorough look over, I discovered numerous issues.
1) Missing crystal at Y3
2) UE20 was obliterated
3) C125 was cracked in half
I replaced those items and tested for continuity on everything because with the damage that was done to UE20, I was suspecting to find open traces around the chip feet that were forcibly broken. I ended up finding three open traces. Installed some quick jumpers and powered up the board...
Minor success. Board booted, but had ram errors. UB12 and UB14 were registering as bad. The ram chips are almost NEVER actually bad. 99% of the time, it's something else that's causing the issue. So the troubleshooting continued. Tested for continuity between the bad rams and the good rams. Found three points that tested bad. After inspecting the traces, I found the issue...
4) A deep gouge that had opened three traces.
Added some quick jumpers and powered up the board...
Another step in the right direction. UB14 was now good, but UB12 was still bad. Completely re-flowed UB12. No joy. Using a 'parts' board as a reference, I began hitting the items interfaced with UB12 for continuity. Started with UC12 and immediately found the issue...
5) Two pins on UC12 were shorted internally
Replaced UC12 and powered up the board. SUCCESS!! The board appears to be fully working now with no defects noted. Total cost - $25. Just wanted to share another successful repair. Thanks!








Initial symptom - Dead. DOA. Nothing. Paper weight.
After giving the entire board a good, thorough look over, I discovered numerous issues.
1) Missing crystal at Y3
2) UE20 was obliterated
3) C125 was cracked in half
I replaced those items and tested for continuity on everything because with the damage that was done to UE20, I was suspecting to find open traces around the chip feet that were forcibly broken. I ended up finding three open traces. Installed some quick jumpers and powered up the board...
Minor success. Board booted, but had ram errors. UB12 and UB14 were registering as bad. The ram chips are almost NEVER actually bad. 99% of the time, it's something else that's causing the issue. So the troubleshooting continued. Tested for continuity between the bad rams and the good rams. Found three points that tested bad. After inspecting the traces, I found the issue...
4) A deep gouge that had opened three traces.
Added some quick jumpers and powered up the board...
Another step in the right direction. UB14 was now good, but UB12 was still bad. Completely re-flowed UB12. No joy. Using a 'parts' board as a reference, I began hitting the items interfaced with UB12 for continuity. Started with UC12 and immediately found the issue...
5) Two pins on UC12 were shorted internally
Replaced UC12 and powered up the board. SUCCESS!! The board appears to be fully working now with no defects noted. Total cost - $25. Just wanted to share another successful repair. Thanks!





















