This isn't the original "original" AT hard drive, which was a 20MB.
I'm guessing that it was the later 30MB one with the voice-coil
positioner. If that's so, you can tell by U24 and U16 being 74LS374s
on the PCB. I've got the schematics from the O&A, which run to about
18 pages if that will be any help.
Nothing much in the O&A text itself, which has a few typos.
Cheers,
Chuck