3 Apr
2015
3 Apr
'15
1:14 p.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of tony
duell
Sent: 03 April 2015 18:44
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: RD54 Stopped Spinning
I am going to try to answer several points together.
The mystery component sounds like a crystal or ceramic resonator. Does it
connect directly to the Z8, if so, to what pins? 1k is a very low DC
resistance
for
such a component, though (was this tested
out-of-circuit)?
No, it was tested in circuit. It is rather hard to tell what it is connected
to actually, the traces are not clear as there seem to be a couple of
layers, and probing with a DMM appears to show it not connected to anything
on the Z8.
The RD54 is a Maxtor XT1140 or something similar. The spindle motor is a 3
phase electronically-commutated thing (no brushes -- does _any_ small hard
disk have brushes in the spindle motor [1]). It is entirely within the
HDA, there
must be some hall effect sensors that are part of it
(inside the HDA too)
for
position feedback.
Alas I have never seen a schematic for this drive (it's not on bitsavers
that I
can
find) so I don't know many details.
Assuming the power transistors are good, then the most likely fault is a
failed
hall effect sensor, inside the HDA.
If we could find a pinout of the motor cable, or a schematic for the
drive, it
would be possible to see what is going on there.
There is a partial printset on bitsavers, but sadly it seems to be missing
the real meat.
(http://www.mirrorservice.org/sites/www.bitsavers.org/pdf//dec/disc/MP02291_
RD54_sch_Jun87.pdf).
[1] Some larger hard drives, the Diablo 30 springs to mind, had brush-type
DC
permanent magnet spindle
motors (and in the case of the Diablo 30, positioner motors, but that is
another
saga). Many full-height
5.25" floppy drives have permananet magnet brush-type spindle motors (belt
driven to the actual spindle.
But I have never seen an 8" or 5.25" winchester drive that does.
> Interestingly at one point it started working again. Then after I put it
all
back
together again, it stopped working
> once more. In one case, it seemed to start spinning when I changed the
disk's
orientation (on its side rather
> than flat), almost as if it just needed a mechanical encouragement to
get it
moving. But now, no matter how
> many times I try, and what different orientations I try, it doesn't
work.
Does
any of that help with pointing the
then
finger at all?
Maybe if one hall sensor or drive to one of the motor phases has failed turning the drive moved the spindle
just enough to get another motor phase energised and it started running
(possibly not on all 3 phases properly),
That is consistent with what happened.
It looks like I would need to open up the drive. Of course I don't have
access to a clean room. Does anyone have any advice or suggestions on how to
make a "clean*er*" room in an ordinary home?
Regards
Rob