Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!sdd.hp.com!decwrl!btr!thad
From: thad@btr.BTR.COM (Thaddeus P. Floryan)
Newsgroups: comp.sys.3b1
Subject: Re: Different boot problem...
Keywords: 3b1 boot
Message-ID: <1974@public.BTR.COM>
Date: 1 Mar 91 11:12:56 GMT
References: <12744@helios.TAMU.EDU> <1991Mar1.045750.19952@i88.isc.com> <12877@helios.TAMU.EDU> <12880@helios.TAMU.EDU>
Distribution: comp
Organization: BTR Public Access UNIX, MtnView CA, Contact: cs@btr.com 415-966-1429
Lines: 21

In article <12880@helios.TAMU.EDU> n138ct@tamuts.tamu.edu (Brent Burton) writes:
>[...]
>The voltages were the same as I mentioned in my last posting.
>EXCEPT the -12V (pin 18 on the PS-->MB cable) was +0.79V.  This is
>a bad sign.  What hints are there?

Sounds like a bad -12V IC regulator.  As I recall, the -12V regulator is
right at the front of the power supply, so replacing it should be
straightforward.

Not too much on the system uses -12VDC, and I don't believe anything could
have been damaged by the voltage you measured, but what concerns me is what
caused the IC regulator to go belly-up.  If it's a problem with other
circuitry in your system, then you gotta problem.  Maybe temporarily using
an external power supply may help isolate the trouble area if there is a
problem on the motherboard.

If you need the power supply pinouts (part of one of my regular postings in
this regards), send email.

Thad Floryan [ thad@btr.com (OR) {decwrl, mips, fernwood}!btr!thad ]