I've got a 9121D floppy subsystem that fails to
pass POST. Drives wink
on power up, fan turns, fuses check out ok, but indicator LED on circuit
board never comes on and drives remain invisible to IB controller (1630G
logic analyzer). I've blown out the dust, reseated cables and the one
socketed PROM and that's all I can figure out to do. Nothing seems
obviously damaged or smoked.
[...]
Obviously, service data or trouble-shooting ideas
would be welcome