CDC 9429 Floppy maintenance manual

Philip Pemberton classiccmp at
Sun May 8 16:33:55 CDT 2016

On 08/05/16 21:49, 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

My awards list more or less goes as follows:

Hardest to align: Nintendo Famicom Disk System.
  For bonus points, when you replace the drive belt, you have to realign
the drive hub, which sets the "start of track" position. There must be a
jig or procedure to do this, but I've never seen it. Homebrew procedure
is to loosen the hub and rotate it a few degrees until things align and
the drive works...
  The hub alignment, incidentally, is critical because the discs are
written as a continuous spiral track, not a series of concentric tracks.

Nicest half-height 5.25in: Teac FD-550 series
  I love these drives to bits. There are a bunch of variants (40/80
track, 1.2Meg and 360K) but they're pretty solid performers. Fairly good
at reading crusty old disks. Keep a few Bemcot wipes and some isopropyl
around to clean the heads.

Weirdest drive interface: the NEC 8-inch drive
  Uses something called a "VFO" interface (I think I remembered that
right?), which is a Japanese standard. Also needs to be rejumpered to
provide raw data output. This is jolly good fun, because the jumpers (if
memory serves) have quite odd labels...

The "What were they thinking?!" award: Amstrad 3-incher, made by Panasonic.
  PC style power connector pinout. With the 5V and 12V swapped. You can
bet every one of these you'll find that's been "tested working, motor
spins when powered but that's normal" will have a fried ASIC.
  Again, has a drive belt, but at least you can replace this without
cocking up the alignment.

For 3.5in PC drives, I quite like the Sony drives. From experience with
DiscFerret, they're pretty good at pulling a clean signal off discs some
other drives won't even read. Some Panasonic drives are better built,
though. Apples and oranges.

classiccmp at

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