11/34a problems continue
fireflyst at earthlink.net
Wed Mar 8 18:40:06 CST 2006
Well, actually the reason I replaced that particular module is because the
board blew. I got a used replacement from the DEC salvage guy I usually
deal with and it came back to life - sans the H745 coming up.
> -----Original Message-----
> From: cctalk-bounces at classiccmp.org
> [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Tony Duell
> Sent: Wednesday, March 08, 2006 6:29 PM
> To: cctalk at classiccmp.org
> Subject: Re: 11/34a problems continue
> > I just replaced that unit recently, so I really don't think
> it's at fault.
> > I suppose it could be.
> Please stop guessing and start measuring!
> In other words, stop swapping modules at least until you have
> some idea as to where the fualt is. I've suggested the 15V
> supply is missing. I might be right, I might be wrong. What I
> meant by that suggestion was that if it was my machine, I
> would now stick a voltmeter on the 15V supply to the
> backplane and see if it was correct or not. If it was, I'd
> check it at the -15V brick too (been caught by bad
> connections too many times!). If it was right there, I'd
> delve into the brick. If it was missing at the backplane, I'd
> check back to the +15V regulator PCB, etc
> You've swapped out a couple of parts so far I believe. Do you
> have any reason to believe that the replacements are good?
> Only last week I had 3 disk drive spindle motors behave the
> same way (spin up, run for a few seconds, then stop), and I
> thought the problem was in how I was driving them. Not so,
> all 3 had much the same intenral fault!. These DEC power
> bricks can suffer from dried-up capacitors, that could well
> be a problem with your 'spare' unit too.
> The first stages of tracing this fault properly need nothing
> more than a multimeter. And I can't understand how anyone can
> hope to maintain a minicomputer without that instrument.
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