Shugart 800-8 media centering problem

Jay Jaeger cube1 at
Sat Aug 15 12:37:35 CDT 2015

On 8/15/2015 11:59 AM, Chuck Guzis wrote:

> I went and stared at some of my 8" drives for a bit this morning.
> It occurs to me that if your top guide frame is laterally "warped", the
> centering of the hub clamp assembly won't work.

Agreed.  But the darn thing is cast, with lots of fillets for support.
I wonder how it would ever get warped, short of something REALLY heavy
being dropped on it, or it itself being dropped from a considerable
height - and there is no evidence of that.

However, I thought I would test an SA 801 (jumpered as an SA 800) on the
thing, so I could test the controller at double density.  When I did
that, something died (smelled electronically burn-y) after a few seconds
of OK operation.  Not sure if it was one of the tantalums or the stepper
or something else, though.  Anyway, I now have a drive that I can pull
the clamp arm out of (the top guide frame, as you say) and try in the
failing drive, to see if I can nail it down to that part of the spindle,
just out of curiosity.

> If you've got a wiggler gauge handy, you may want to see what the
> deviation is when the hub clamp mates with the spindle hub assembly.
> While you're at it, you may want to check the spindle hub itself to see
> if it's not out-of-round.

Don't have a wiggler gauge, or anything to use it with.
> There's a patent 3,898,814 on the Shugart clamping system that many
> manufacturers licensed.  Perhaps it can shed some light.
> --Chuck

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