Bad wiring?

Thanks for the comprehensive reply; I'll print it out at work tomorrow & follow through. I just think it's odd I've blown 2 PSU's on a fairly new machine, and now the one in the HP on the same day. That's what makes me question the wiring in this room.

Thip wrote:
Thanks for the comprehensive reply; I'll print it out at work
tomorrow & follow through. I just think it's odd I've blown
2 PSU's on a fairly new machine, and now the one in the HP
on the same day. That's what makes me question the wiring
in this room.

Based on your IP, you're in the US somewhere.

The power would be 115V on two phases. When you use
both hot legs, you get 230V. One hot with respect to the
center tapped neutral, gives 115V.

Now, say your neutral was broken somehow. I got to see this
at work once, where one of four branch circuits in the office,
ran at 90V instead of 115V. I've also seen it in an entire neighborhood,
where line voltage is abnormally low (due to some conductor opening
at our substation, about a block away). Even the traffic lights
were low in that case.

If the neutral isn't in the center of the two lot legs, one
hot will have a higher than normal voltage, the other lower
than normal.

Usually, your incandescent light bulbs are a good means of
detecting that problem. Lights will "pop" more frequently, if
on the high leg, and be "brownish" in color if on the low leg.
The incandescent bulbs will be visible "wrong", well before you
get to a point that an ATX supply will be damaged.

Below perhaps 90V, the ATX PSU might have a bit of trouble delivering
output voltages (if a fair load was present). If the AC input goes
high enough (like above 130VAC), eventually you could reach a point
where the main capacitors will exceed their working voltage rating.
Now, if that happened, I would expect a pretty significant noise to
accompany the event. It might not be a mild "pop". As far as I know
(with the exception of my Apple computer), there is no relay present
inside the PSU, to open the AC before there is a calamity.

Between those two extremes, I would expect your power supply to
function properly.

Open the PSU and do a visual inspection. If you can't see anything,
don't worry. It's just an idea, to confirm a theory if there is easy
evidence present. Things can always fail silently, and have no
visual artifact.

The last PSU I opened, had leaking capacitors inside it, and the failure
was on the secondary side (bad 5V rail). It pretty well looked
exactly like this (orange colored deposit on four secondary side capacitors).
The power supply had very few operational hours on it, and started to
leak sometime during the two years it was sitting idle and unplugged.
The only symptom, was a slight "sizzling" sound during the first
30 seconds of operation. Eventually it became cranky enough,
to cause the computer to crash.

http://upload.wikimedia.org/wikipedi...4/PSU_Caps.jpg

Another thing you can check, is the branding on the power supply.
There is a certain model of Bestec brand supply, that when it
fails, it damages the hardware in the computer. If you're replacing
one of those supplies, it pays to first check the hardware. Like,
unplug the hard drive, and test it in another computer, to see
if it's still alive. Depending on the extent of the damage, you
may want to rethink your repair/replace strategy.

Paul