Apple 3.5 inch Unidisk Drive Analog Card Schematic/Repair Advice?

So I have two Apple 3.5 inch Unidisk drives. One works fine, but the eject motor doesn't push the disc out all the way, but I can live with that. The other won't work at all. When I connect it to my //e, and inert a boot disc, the light flashes, then nothing. I've tracked the issue to the analog card in the drive, as when I swapped the drive itself between the two, the failure remained with the defective board. I've been poking at it with multimeters for months now with no idea what I'm looking for or luck in tracing the problem beyond the board.  I really don't want to throw this thing out. Aside from the high cost of replacement, this was part of my grandfather's //e, so there's a lot of sentimental value as well. So if anyone has a schematic, or any advice on how to trace the fault, I would be very greatful.