billdeg
Technician
maybe it's an AM not an HM. Hard to read. These are the drive select jumpers:
MX
DS3
DS2
AM? [JUMP'R] (or HM?)
DS1
DS0 [JUMP'R]
HS
MX
DS3
DS2
AM? [JUMP'R] (or HM?)
DS1
DS0 [JUMP'R]
HS
Not being a real hardware technician by any stretch of the imagination, what things should I be looking for on the controller card?
replace the 1793 chip on the drive controller (the small card directly attached to the mother board). That might be the entire problem.
HM, HS determine if the head is loaded (for those models with head-load solenoids) on receipt of the MOTOR ON or DRIVE SELECT signals respectively. Teac strongly advises against have both jumpered at the same time. For head-load solenoid-less drives, both jumpers should be open.
Look at PDF page 32 (Document page 229). You'll find your HM jumper there. Nobody said that Teac manuals are easy to read. Very often, several different models/PCBs are discussed in the same manual (you should see the wild assortment in the FD235 manual).