CDC 9429 Floppy maintenance manual

Paul Berger phb.hfx at
Sun May 8 16:02:06 CDT 2016

On 2016-05-08 5:49 PM, Chuck Guzis wrote:
> On 05/08/2016 01:30 PM, tony duell wrote:
>> They are considerably better than the Shugart drives with the plastic
>> disk with a spiral groove for the head positioner....
> Ah yes, the SA-400.  When I was evaluating one, I wondered if Shugart
> was really serious about the things.  Doubtless some engineer at Shugart
> was quite proud of himself for designing a ball-bearing follower for the
> spiral groove.  Marks for being cheap.
> Oddly, my own troubles with the SA-400 (believe it or not, this was used
> as the original IBM offering for the 5150 drive) were with the tach
> circuit.  Mine blew a small inductor.
> Among all of the 5.25" FH drives offered at the time, my vote still goes
> to Micropolis for designing the Sherman tank of drives.  Leadscrew
> positioner with multiple steps per track.  Probably among the most
> expensive 5.25" drives also.
> To their credit, Shugart did have the best hub-clamp setup.
> --Chuck
Are you sure about the SA-400 being used in 5150s?  All the ones I ever 
saw where Tandon TM-100s which look very much like them and I saw lots 
as a support person in an IBM lab in the early 80s.  They have the same 
sort of motor setup to turn the diskette, but use a different head 
positioner.   The TM-100s used a stepper with a taut band positioner.


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