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From: scj@pandora.bellcore.com (Steve Johnson)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Warning about upgrading memory!
Message-ID: <23026@bellcore.bellcore.com>
Date: 9 May 90 12:37:53 GMT
References: <4830@daffy.cs.wisc.edu>
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Reply-To: scj@pandora.UUCP (Steve Johnson)
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In article <4830@daffy.cs.wisc.edu> horn@cat19.cs.wisc.edu (Mark Horn) writes:
>the 3b1 power supply!  Sure enough, I replaced my 7300 power supply with the
>3b1 power supply that I never got around to installing, and I've been running
>fine ever since.
>
>So, after all of that, here's my warning:  If you plan to do this upgrade, make
>sure you have a 3b1 power supply, or you may have trouble booting.  
>
>FYI,
>- sparkie
>--

Upgrading a 7300 PS is a good idea (if you have a 3b1 PS B^) *but* what sparkie
has seen *may* have been the infamous power supply solder joint failure.  Seems
that some, if not all hard drives powered by a 7300 PS (that is, through the
motherboard traces) draw enough power that the solder joints on either the 
power supply side or the motherboard side of the power supply header (that
set of 16-18 STIFF wires going from the power supply to the motherboard on
the right side of your machine) get warm.  *very warm!*  This heat is enough
that, in some cases and over time, an increase in oxidation and/or an actual
melt of the solder occurs.  The combination of the heat, oxidation and
continued neglect (ask me, the man who owns one!) creates a self-feeding cycle
that causes more heat, etc.  Which eventually gave me exactly the symptoms
that sparkie described (HD won't boot).  In my case the plastic connector
was burnt badly as well, so I now have all those wires soldered directly
to the PS and I check the quality of those new solder joints and the old
motherboard solder joints regularly.

As was posted about 1 1/2 years ago, check that PS hardware regularly!
Include the check in your semi-annual dust bunny roundup.