Hey all - Last night started up a game for first time in a week. First ball into the chair, no kickout. Switch didn't respond. Then noticed the GR, It, and Swamp targets also don't respond. So all of column 4. I did the jumper test and confirmed it's a board problem. No response on the column 4 pin for any row. Later on I went to show a friend and did the jumper test again. This time column 5 didn't response either (this is the book case optos, thing flips opto, etc.). The machine shows "check opto" errors at the bookcase and thing flips at startup. I have checked every physical switch in columns 4 and 5 and there are no shorts.

I assume this means a chip or two are bad on the CPU board? Which to replace? FYI all boards are clean, no battery damage. No visible distress to any of the chips on the CPU board. Thanks for any guidance.

Thanks dudes. I will replace that chip and hopefully winner winner chicken dinner.

Replaced U20 today. Column 4 still out. Any other suggestions?