I'm not sure if this suggestion could help, but it might be worth checking. Just looking at the pcb, in the photo of the drive on the right, I think the cylindrical black objects are possibly inductors (should have a low DC resistance), one looks like it has 68UH written on it. Also there are a couple of parts there that look like a resistor, but just with a central black band, probably a 0 Ohm resistor used as a link or a small chance of a fusible resistor. Check these all these parts for continuity with a meter with the drive not powered. If those objects are inductors I have seen some of these small axial ones go open circuit with age. Then with the meter you could easily check the diodes there as a start. But it is always a shot in the dark testing random components and the fault might not definitely reside on the pcb, though its likely.
Also, there may be other inductors on the board to check, the two pale green devices (with stripes) that look like resistors on the left of the white preset potentiometer may possibly be inductors, check them too.