Qume?

From: Tony Duell <ard_at_odin.phy.bris.ac.uk>
Date: Mon Nov 10 04:28:14 1997

On Mon, 10 Nov 1997, Bill Yakowenko wrote:
> But success was not total; floppy drive 0 works fine, but drive 1
> just retracts to track 0 and makes a buzzing/grinding noise. I'm
> guessing that it wants to hit track 0 at the beginning of a seek,
> can't tell that it has made it there, and is struggling to retract
> past the legal limit.
>
> So, is anybody out there familiar with the mechanics of Qume 8"
> floppy drives? Is there a switch or optical sensor or something
> that tells it when it is at track 0? Or, from the description, is
> it possible/likely that this is an electrical failure, like a dead
> chip? Anybody got a service manual for one of these critters?


I don't have the Qume service manual, but I've worked on a number of other
8" drives.

In general there's a slotted optoswitch (an LED and a photodiode mounted
facing each other) that is triggered by a piece of opaque material on the
head carriage. The light is blocked when the heads get to track 0. A few
(a very few) drives used a microswitch instead, but it should be easy to
find out what you have by looking at the drive.

The output of this sensor is sent to the disk controller (the Track00
signal on the cable). Only a very few drives also use it to inhibit the
stepper on the drive itself. But sometimes the Trk00 signal is gated with
a signal that says that the stepper is in a particular phase (the one
corresponding to track 0, track 3, track 6, etc - these drives nearly all
used 3-phase steppers) so that provided the sensor trips somewhere
between track 3 and track 0, it will give the right output.

You problem could be the sensor (unlikely, since common failure modes
would cause it to be 'triggered' all the time), the drive logic, or even a
dead wire in the cable (if the trk00 signal is not getting back to the
controller). It shouldn't be too hard to trace the signal from the
phototransistor to the Trk00 pin through the logic chips, though.


>
> Cheers,
> Bill.
>

-tony
Received on Mon Nov 10 1997 - 04:28:14 GMT