28 Jan
2010
28 Jan
'10
10:02 p.m.
Sometime ago I posted a request for help on my two Compaq Portable IIs that
failed to boot from the FDD.
I now can boot one using an "off the shelf" (at Weird Stuff) half height 360
kB FDD in place of either of the two Canon 5201 1/3 height FDDs that were in
the two Portable IIs. Both exhibit the same failure mode, while trying to
read the disk visibly spins erratically, as if there were some form of
stiction causing it to go slower and then faster. Manually turning it with
and without a disk, the spindle motor feels free of stiction.
It is surprising to me to find both Canon 1/3 height FDDs fail in the same
mode, suggesting a fundamental flaw in the design. For example, the full
Hve you checked -- with a voltmeter and 'scope -- the 12V power line to
the drives? It's possible the original Canon drives need more current
than your replacemetn (enve if they're working correctly) and you have a
PSU problem that is cuaseing the 12V line to dip under those conditions.
If it's certianly the drive (I'd stick it on an exerciser powered by a
known-stable PSU), I'd start ivestigatgn the spindle motor. I assume it's
a direct-drive mortor under the spindle (that's not _always_ the case,
even in slimline drives).. Strip it down and check the windigns for
open-scirucits. Check the outputs of the hall sensrs witha 'scope when
the motor is running. Maybe suspect the motor control IC((if you're lucky
it'll be a stnadard one.
-tony