Shugart 800 spindle bearings (Re: Shugart 800-8 media centering problem)

Jay Jaeger cube1 at
Mon Aug 17 20:48:59 CDT 2015

The bearings were actually easy to replace, no special tools required.
The hardest part was getting off the nut that was holding the spindle

Other than that, the bearings side into place pretty easily (the top
one, which is the most critical, required the heel of my hand to press
it in place in the hole in the deck, that was all).

The whole operation took only about an hour, from start to finish.

For future reference, the original bearings are marked similarly to the

Top bearing (with flange):
   SSR - 4ZZ  NMB

Bottom bearing (no flange)
   NHBB  R4

(It is possible that the replacement bottom bearing had that "R4" as
well, and I missed it).

Once I get the power supply fixed, I'll test the drive to see if this
helped.  If there is ANY difference, maybe I can move a
shaft/screwdriver inserted in the old bearings just a little bit further
from vertical - they allow a tiny bit more rock.


On 8/17/2015 4:22 PM, Jay Jaeger wrote:
> Well, in the process of repairing the Altos power supply I managed to
> break the center lead off of the TIP31A that feeds the 2N3055 series
> pass transistor.  This time, I need to order parts.
> In the meantime, I swapped drives to make the problem more drive accessible.
> Also, the Shugart 801 drive I was testing is part of a pair in a Data
> Systems ADS-440 dual floppy system intended for use in a PDP-11 that I
> have never used.  (Would have to look - looks like it needs its own
> special interface card).  Along with that machine, which came from or
> was at least touched by the U. Wisconsin Instrumentation Systems Center
> (ISC) back in the day, came a set of (gasp) brand spanking new bearings
> for a Shugart 8" drive.  Looking at the parts diagram, I think I'll pull
> the spindle apart while waiting for my power supply parts, and see how
> hard it would be to replace the bearings.  Not all that hard, I'd think.
> For future reference, the bearings are:
> Part #9 in the diagram - flanged bearing markings:
>    SSR - 4HH    NMB
> Part #8:  - (unflanged) bearing markings
>    NHBB
> NMB still exists as part of Minebea Mineature ball bearings.
> NHBB still exists - New Hampshire Ball Bearings
> The new old stock bearings are a little stiff, but will roll when held
> against a piece of paper.

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