Stan, It is not 2-3V of DC for motion. The processor won't start up at that level and even if it was running, that is not a high enough voltage to come out of neutral. Joe confirmed how the boards work in DC as I mentioned. Please let us know which chip is this simple converter? I just do not see how the Processor if it thinks it is in DC but see 0 VDC, or let's say it think 12VAC is 12VDC. If so it should move. Otherwise a small 3-5V DC offset is not high enough to determine that is the command to go. The engine would sit at idle with 8 to 9V until it got a high voltage spike. Frankly, it is more likely the main rectifier got damaged, and the motor leads have AC on them and the DC offset causes motion. But as I stated before, track power and Signal transformer power do go to the main processor. So if it took a hit, no can fixxy. I just don't think the DC offset is of the level in DC voltage that the processor would think it should command motion.
If OP wants to send me the board I can test and diagnose. But I think a diode took a hit and the offset is getting on the motor leads circuit to drive the motor. G
