With power applied to the drive, what voltage do you see (with respect to 0V) on the bar / striped end of diodes CR7, CR8 and CR9? They are the diodes which are right on the edge of the PCB next to the regulator heatsinks.
Diagram etc for the 3040/4040 is here:-
http://www.zimmers.net/anonftp/pub/c...schematics.pdf