SA-400's (was: Heatkit 5 1/4 floppies - test-drb@ccmp.vtda.org

7 Apr 1999

I don't know about designators, but the first mini-floppy drives I got all
had lead screws like the 8" drives.  Later on, the SA400-<something> became
available, and I don't remember what the <something> was, but they had the
helical cam with a 2-phase stepper.

Dick

-----Original Message-----
From: Fred Cisin (XenoSoft) &lt;cisin(a)xenosoft.com&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Wednesday, April 07, 1999 5:41 PM
Subject: SA-400's (was: Heatkit 5 1/4 floppies

...
 On Wed, 7 Apr 1999, Richard Erlacher wrote:
> I don't believe those were the earliest of the 5-1/4" types.  The early
> SA-400's I remember used a lead screw just like the 8" drives, but that
was
...
 > too costly for the competition that followed. 
When Apple started buying
> "partial" drive mechanisms in order to implement their more
software-driven
...
 > approach, with the idea of saving a few bucks . .
. multiplied by a milion
...
   or two drives
. . . other manufacturers including SIEMENS and BASF, among
 others, tried a two-phase stepper on a helically-tracked drive wheel as
 opposed to the stepper driving a lead screw.  Most makers later went to a
 band-actuator system using a small stepper. 
Interesting.  All of the SA400s that I've seen used the spiral groove on a
rotating disc.  The only 5.25" drives of that vintage that I have with a
helical lead screw were the Micropolis 35 track 48TPI and 77 track 100TPI
(NOT 96TPI!!).  Was there any sub model designation for the Shugarts to
differentiate different positioners?

--
Fred Cisin                      cisin(a)xenosoft.com
XenoSoft                        http://www.xenosoft.com
2210 Sixth St.                  (510) 644-9366
Berkeley, CA 94710-2219