I replaced the SMD electrolytics with tantalum caps on this Macintosh II board 820-0228-A. The board boots, and sound is good, but the video appears with a scrambled pattern. I can see the cursor move between the broken up columns. I'm using a known good Macintosh Display Card with correct DIP switch settings. I've tried booting with known good RAM SIMMs pulled from working earlier revision Mac II boards. I did find a broken trace from D5 to B1, I bodged that with some wire and ensured continuity. Nearby the broken trace, UC7 was the worst-looking chip on the board with highly visible corrosion. I removed it to clean it up and reinstalled but the issue persists. Looking around the NUCHIP, nothing looks visibly awry. I've checked more traces but I'm running up against the limit of my abilities.
Any suggestions on further troubleshooting would be appreciated!
Any suggestions on further troubleshooting would be appreciated!
