19 Oct
1999
19 Oct
'99
1:07 p.m.
Yes, I believe I have one. I can't lay hands on the manual right away, but
maybe by 10:00 pm (it's about 6:20 pm now) I'll have it in hand.
IIRC, the index pulse is generated from a hall sensor which looks at the
spindle. So long as you get only one index pulse per revolution, and so
long as those revolutions are close to the rated speed (60 Hz) they should
satisfy nearly any controller's needs and allow the drive to be low-level
formatted.
Dick
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, October 19, 1999 3:33 PM
Subject: Fixing an ST412?
Short question : Does anyone have a Shugart ST412
service manual?
Long Question : As some people here know, I'm slowly rebuilding a DEC
rainbow. And today it got to the point where it was worth trying to boot
it. It booted fine from the RX50 floppy drive, but not from the RD51 (aka
ST412) winchester.
A little bit of probinf with a LogicDart revealed that the drive was
producing no index pulses, although it was spinning. There are schematics
for the older version in the IBM O&A techref, and using these as a
reference, I quickly found that the index sensor itself was producing no
output.
Off with the logic board, and I found that the index sensor was loose in
the clamp, and about 1/4" from the arms on the motor that trigger it.
I adjusted it closer, tightened it up, put it all together, and it seems
fine. The 'Bow boots from the winchester and seems to be able to run
programs, etc.
What I want to know is is there a proper procedure for adjusting this
sensor? Is there a particular value quoted for the gap between the sensor
and the arms?
As I said, it's OK now, but I might as well do it right.
-tony