I'm working on a T2 with Column 2 not working. The thing I can't figure out is that it's working enough to let the game boot and play. Let me explain:

Column 2 is the one that contains the "Test Position Always Closed" switch (#24) that allows the game to "see" that the switch matrix is receiving power. If I try to boot the game without J207 connected, the game (obviously) doesn't work and reports the "Check Fuses F114 and F115" error.

Now here's the screwy part: no other switches in that column work. Even at the MPU, shorting row headers to the the column 2 header directly with a wire & diode shows no action on that column, so I'm convinced the issue is on the board. I replaced the ULN2803 and the problem persists. Before I move to the LS374, I want someone to convince me I'm moving in the right direction (or not). It seems odd that the whole column is out except for that one "normally closed" switch.

Board is corrosion-free.

Any help would be greatly appreciated.

Corey

I have confirmed continuity from J206 and J207 through to each of the appropriate pins on the ULN2803. I have not confirmed continuity between J212-2 and J206-2. If there isn't continuity there, what would that tell me? I also haven't yet confirmed continuity between J206-2 and C12 or R68.

Thanks for the advice. I just went ahead an replaced the LS374 and the issue has now been resolved. The old chip tested bad in my tester. All good now.