Re: DISK II DRIVE: Which "daughterboard" IC's control speed?

[dalloff@freenet.columbus.oh.us (Dave Althoff)]

Get out a multimeter and check that speed adjuster.  That should be about
a 20-turn potentiometer, and if you look at the case, it is probably
stamped or imprinted with the maximum resistance rating.  It could be that
the pot is faulty, or simply stuck.  You can check the resistance across
the full coil, and between each end of the coil and the wiper (sorry;
without looking, I really can't tell which pin is which).  Anyway, when
you turn the set screw, the resistance between the coil-end and wiper
should change.  If it doesn't, yank that unit out and replace it (it's
only three solder points!).  I'd look there first, since I think you can
just unplug the drive and test that part without taking it out of the circuit.

That's my guess...
--Dave Althoff, Jr.