PerSci Model 277 Dual 8" Floppy Drives - Info Needed

From: Jim Battle <frustum_at_pacbell.net>
Date: Mon Jan 20 16:06:01 2003

At 09:57 PM 1/17/03 +0000, Tim Myers wrote:
>Does anyone have any info on these drives? I have some in a CP/M system
>(Ithaca Intersystems DPS-1), and they seem completely dead. They have an
>electric load mechanism, but when I insert a disk, nothing happens.
>Popped the case and can't see anything obviously out of place.
>
>Tim.

I have the manual for that drive. My copy was published by processor tech,
but it was just relabeled info from the original data sheets. It contains
schematics for all the boards (something like 7) in the drive, and
information on aligning and servicing the drive. it is quite a bit of
information.

I'm in the process of debugging a couple of helios drives, but the project
has been stalled for a few months due to work demands and a lack of
long-term debugging space.

I have found a couple problems and the drives still doesn't work. The
first problem was that a cap on one of the boards had developed a short,
and when I turned power on, it would cause the voltage regulator for the +5
line to shut down, making further debugging hard. I ended up removing each
board from the power supply until I figured out which one had a problem,
then it was fairly easy to guess which component was the bad one (no marks,
but the caps were the only parts going from power to ground. all other
paths would have required at least two series parts to both develop shorts,
which seemed unlikely).

Another problem was a 74121 had an output go bad, making the part look like
it was always triggered. This prevented the head from seeking to a
different track (HOMEing to track 0 worked, though).

One problem is that the schematics in the manual are for a different
revision of the main board with all of the control logic. They are similar
enough that the schematic helps, but different enough that you must double
check everything.

Please contact me off list and we can try and work out some sharing
arrangement, or copies of specific sections.

-----
Jim Battle == frustum_at_pacbell.net
Received on Mon Jan 20 2003 - 16:06:01 GMT