I received an A9M0107 5.25" (1986 Unidisk) floppy drive with a IIgs I bought recently. When attached to the computer, the LED flashes briefly a few times at power-up, but otherwise it shows no signs of life. There's no motor movement, and GS/OS doesn't show it in the Finder. I know the Smartport interface is fine, because I'm able to read/write disks using a different drive.
I disassembled it as far as removing top analog board, and there's nothing obviously wrong with it. There's some factory rework evident by leftover flux and obvious hand soldering on the DB19 and the trim pots, but the pots still have the factory epoxy on them.
I searched for a service manual or photofact, but I haven't found anything.
Any tips would be appreciated!