CompuPro floppy controller differences

dwight elvey dkelvey at
Sat Sep 23 12:31:57 CDT 2006

>From: "Chuck Guzis" <cclist at>
>On 9/22/2006 at 7:24 AM dwight elvey wrote:
> >Although not recommended, years ago we got some 8 inch drive at surplus
> >that were 50Hz. The drives were cheap and we didn't want to invest a
> >lot. We simply ground down the motor pulley with a file. We checked our
> >progress with a strobe disk on the flywheel. It did require elongating 
> >mounting holes for the motor.
>When I wanted to use a 50Hz 8" drive on 60Hz, I worked out the size of the
>new pulley, went to Halted and dug around their parts bins.  I came up with
>something of the right diameter and shaft size, but made for a toothed
>timing belt.  Not "crowned", but it had flanges to keep the belt in place.
>I used it for almost a decade, running the spindle motor from 240v 60Hz,
>courtesy of a linear P/S with 2 primary windings hooked in series as an
>autotransformer.  I didn't have a lathe back then; if I had to do the same
>thing today, it'd be a simple matter to turn a new one.
Hi Chuck
We did similar but used a file to reduce the pully size with the motor
spinning. We also used the input leads of a transformer as an 
to reduce the voltage. Using cogged belts for drives can cause
jitter that makes it hard to write and read data. It is true that
most are more forgiving of the motors pulley but I've had cases
where small corrosion on the flywheel surface where the belt
rode was enough to cause problems.
Halted is a local ( Sunnyvale,Ca, USA) surplus shop, for those not
from this area.

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