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.
On Sun, 8 May 2016, Paul Berger wrote:
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.
The first 5150s that I had, or saw, had Tandon TM100-1 (single sided).
Followed (along with PC-DOS 1.10) with the TM100-2 (double sided). Later,
I started to see some other brands of drives used by IBM in 5150s, but
NEVER Shugart SA400.
It would have at least had to be the SA400-L, since the SA400 was 35
track, and PC-DOS, from the get-go, used 40 tracks.
The SA400 was, however, the original offering for the TRS80. Followed
later by TM100-1 and a few others.
And the SA390 (same mechanism, but without the circuit board) was used as
original offering for Apple. There was an unconfirmed rumor that, for a
while, when they ran short, that Apple bought SA400s and removed the
board.
I agree about Micropolis; it was the most reliable drive that I had,
although kinda slow stepping.
The LEAST reliable drives that I tried were the BASF 2/3 height, followed
by the Qumetrak 142 (early 1/2 height)
Worst problem that we faced with the TM100s was that students in the
computer labs would let the door slam when opening, breaking the hinge.
