One wonders exactly what happened to these, I'm going to have to press the guy on what he did. 
I created this problem just the other day by accidentally shorting the heating elements to the metal in the smoke unit in a slave B-Unit after changing the wick. After some fascinating blue sparks (from the 18V AC common to the heating element), the engine:
1) doesn't click the relay when applying power.
2) doesn't click the relay when switching forward and reverse.
3) doesn't have sound.
4) only goes forward very fast when rolling the speed from 0 to anything.
5) it will stop when rolling the speed to zero.
6) lights do work, but I didn't pay attention to changes with direction.
7) didn't try in conventional, or try turning the smoke units on/off.
Something definitely got burnt because I could smell it from the board, but I can't see anything that looks burnt.
I changed out the Ps2 boards today and tried it with the unchanged slave unit, and everything worked fine. I feel a tiny bit lucky that the slave board is fine since it's much more annoying to find.
I'll be watching this thread to get ideas on salvaging something from my slightly toasted boards. Is there any wiring diagrams or other troubleshooting documentation available for Ps2 boards?
Eric
