[PLUG] Hardware failure

plugng3 at martinconsulting.com plugng3 at martinconsulting.com
Tue Apr 12 14:46:48 UTC 2011


Dick, 

> When I got up this morning and went to check my e-mail, I moved the mouse
to wake up the screen, but nothing happened. The fan on my desktop machine >
was still running, but the machine otherwise appeared dead. I tried holding
the power button in, but nothing changed -- the fan kept running. I pulled
the 
> power cord from the back of the machine and the fan stopped (of course).
After several seconds, I plugged the power cord back in and tried holding in
the 
> power button. Nothing happened.

> Obviously, something about the hardware has failed. I'll open the box
later and look inside, but I doubt that will enlighten me very much. Any
ideas on what to > poke at?

Caveat:  I have essentially no training in electronics, but lots of
experience in resolving failing hardware.  There may be some witch-doctoring
nonsense in my notes below, but it works for me.

1) I'm suspicious of the power supply.  I've never heard of a recent (last
decade) power supply that wouldn't power down if you held the power button
down for 10 seconds.

2) While you've got the case open, check for bad electrolytic capacitors.
This is a 5-second check (once you know what to look for) that can save
hours of diagnostics.  Here's a reasonably good article on that:
http://www.capacitorlab.com/visible-failures/.  In the first picture, I
count three good electrolytics, in the upper left, center, and bottom.  The
rest are all bad.  This is an extreme case, as I usually only find one or
two bad.  It doesn't matter where you find the capacitors (anywhere on the
motherboard, on a PCI board, etc.).  If they bulge, they're bad.  They might
still work for a while, but they're failing.

3) I once spent two hours trying to diagnose hardware problems before taking
a machine into the shop where it worked fine, and continued to work fine for
a couple of years after that.  The tech recommended for next time: "Before
you get too involved, turn it off, unplug every wire, leave it for about 20
minutes, and try it again.  Sometimes electronics can get in an incorrect
state, and a complete power-down and discharge will allow them to reset."

4) If all that fails, unplug every component you can do without temporarily
(every PCI board, all USB devices, extra hard drives, DVD drive), then see
how it does.  Devices can fail in ways that cause them to flood a machine
with meaningless signals (at least that's my theory).  I have a machine
right now that will take way too long to run its POST memory check if a
particular external USB hub is plugged in.  Once the machine is up, plugging
in the USB hub is fine.  I think the hub must be slamming the bus with noise
until the O/S gets far enough up to reset it somehow.

Good luck.

                                     -Brian





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