[sebhc] Floppy drive circuit boards

Barry Watzman Watzman at neo.rr.com
Thu Sep 21 15:02:53 CDT 2006

In general, no, there are no adjustments on the board related to the
specific drive mechanics, with one exception:  The motor control circuit of
the Wango / Siemens has a pot to adjust the disc rotational speed.  This is
not common but is a characteristic of this particular design.  But in
general, you can swap a drive PCB between drive chassis with no concern for
any differences between the chassis (presuming that we are talking about
working drives and chassis).

Note that you could have seemingly identical drives and boards with some
major differences (e.g. the Tandon 48 tpi and 96 tpi drives look identical),
but the boards will have different part numbers at the highest level (the
actual differences may be nothing more than jumpering or parts values of
circuit boards that are, in fact, identical).  But I'm not aware of any such
differences in seemingly similar boards from the Wangco / Siemens family of

-----Original Message-----
From: sebhc-bounces at sebhc.org [mailto:sebhc-bounces at sebhc.org] On Behalf Of
Mark Garlanger
Sent: Thursday, September 21, 2006 3:44 PM
To: sebhc
Subject: [sebhc] Floppy drive circuit boards

Does anyone know if the circuit board (the one physically connected to
a floppy drive) is calibrated (or otherwised tuned for the mechanical
part of that particular drive? I have two of the Wangco model 82's
that have different issues. The first one fails the seek test even at
36 msec. The second pulls down the 12V supply line. I didn't know what
could be done with the first one, so I attempted to fix the second
one. It had an obvious burnt inductor 'L5'. But, from looking at the
circuit diagram and what little I remember from EE, it didn't see how
this would explain the problem with the 12V supply. So, maybe there
are other damaged parts on the board. Due to this and not having an
inductor on hand, I thought I would use the board from the drive with
the seek problem to see if I could make one working drive (both
circuit boards looked identical and have the same number on them -
although one drive has a red led and the other has a yellow). When I
tried to use the newly created drive, it sounded awful, and did not
work. I was wondering if anyone knows if this could be related to the
'foreign' circuit board? I'm thinking, it's more likely that there is
a mechanical issue with this drive which may have cause the burnt
inductor on the original circuit board. If that is likely the case,
I'm not going to spend the time to try and repair the original board,
but if could be related to the foreign board, I may track down the
parts and attempt to fix it.

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