On Sat, 6 Oct 2007 22:07:11 +1300, "~misfit~"
<misfit61nz@yahooligans.co.nz> wrote:

>Somewhere on the interweb "kony" typed:
>
>
><snip>
>
>> I suspect you have failed capacitor(s) in your power supply.
>
>I had that last week on one of my older machines. Scared the bejesus out of
>me:
>
>http://test.internet-webmaster.de/upload/1191392010.jpg

Unless the fan fails, I seldom see those high-side caps
fail, it's almost always the ones after the transformer
output is rectified in the LC circuits, either the 3.3/5/12V
rails or the 5VSB.


>That's what it looked like after I plugged the PC in (with the side off and
>my ear right next to the PSU). Went off like a shotgun. Luckilly I still had
>my hand on the power cord, I unplugged it in about 0.002 sec. I found an
>Enermax supply that had died a quiter death a while back that had a pair of
>Rubycon caps in it the same size and specs as this and the one next to it. I
>replaced them both and the PSU is running fine again.
>
>[Warning: There can be dangerous voltages present acroos the bigger caps
>like these even if your PSU has been turned off for a while. (mine sparked
>against the soldering iron) I don't recommend that you open PSUs yourself
>ubless you know what you're doing]
>
>I know that's not exactly what you mean by failed capacitors Kony but I had
>to share. :-)

Normally the PSU 5VSB and some parallel resistors drain
those caps down to a negligable level. I'm wondering if you
either had (have) another fault still, or if the remaining
voltage on the caps was low enough to be safe, even if a bit
startling.

Certainly if a high voltage cap fails it has to be replaced,
but the more common failures are the caps around the
existing wiring harness connection to the PCB, or (still in
the same general vicinity on the PCB) one set of inductors
before that point.