I have a pair of PS/2 3V processor boards with a symptom I haven't seen before. I've swapped the power supply with a known good one from a working set, so I'm pretty sure this is really the processor board.
When I turn the board on with a TIU connected, I don't get a relay click. However, I can add the engine and start it up under DCS control. However, I can only go forward, even though the board thinks it's going in reverse, the motor is still going the same direction. Another issue is that when they came in, the audio amp was toasted, I've removed the old one so it won't affect the operation. I didn't feel like putting one on unless I could figure out why the relays don't pick. The only diagnostic help in the ASC manual is to "check K1 for proper operation". Well, it's not operating, that much I know. The other suggestion is a replacement on the power board, clearly that isn't my issue, when I move the power supply to a good processor board, everything works fine.
Any idea which component to look at next?