John Gordon wrote:
> I'm having trouble with my PC hardware, and I'm hoping someone can offer
> some advice.
>
> Two nights ago, I came home from work as usual and turned on my PC to do
> some web browsing. After just a minute or two, the PC suddenly shut itself
> off.
>
> I waited a minute and turned it back on. Everything came back okay, and
> I launched World of Warcraft. I had barely gotten logged in to a character
> and again the PC shut itself off.
>
> So I unplugged it and took it out to the porch to blow out the dust.
> There was some (we have three cats), but not an excessive amount. I put
> the side panels back on and plugged everything back in then turned it on.
>
> Nothing happened. The fans did not spin, no humming noise, nothing.
> Well, actually one small LED on the case top did come on. I think it's
> the hard drive activity light.
>
> And -- here's the bad part -- after ten seconds or so there was a
> noticeable burning smell, so I quickly shut everything off and unplugged
> it.
>
> I don't know specifically where the burning smell was coming from, but
> the fact that the fans did not spin up leads me to think it's the power
> supply, and I might be able to put things right with a new one.
>
> Am I right in thinking it's probably the power supply?
>
> My PC is old enough that it may be time for a new one, but it worked just
> fine (until the burning smell of course) and if I can get it running again
> for the cost of only a new power supply I'd love to do that. I don't look
> forward to spending $800 or so on a new PC.
>
> Any advice?
>
No one has mentioned the topic of collateral damage yet.
There are some power supplies, that when they die, they damage
stuff in the computer. There is a Bestec brand supply that does that.
When it dies, it's something like the 5V rail that goes above its normal
voltage. Directly connected components (motherboard, hard drive, CDROM, keyboard,
mouse perhaps) are at risk, while memory and CPU may survive and be reusable
in a new motherboard.
I'd say chances are good it won't affect you, but take a look at the
label on the power supply and see what brand it is.
*******
If you're new to changing supplies, it helps to take notes of where the wires
go, and where "pin 1" is. For example, the rule I remember, is the yellow wire
goes on the outside, for the hard drive and optical drive. Just write
down what you see, on a sheet of paper.
A trouble maker, is the floppy connector. It wobbles up and down a bit,
and needs to be wobbled before it can be retracted. Also make note of the
wire colors. I think it's keyed so it only fits one way, but it never hurts
to be sure of your wire color.
Many of the connectors are keyed, and have unique shapes in the connector shell.
The IDE drives, they may have a keying pin, but you won't find the keying pin on
all of the cable assemblies you own. Look for a red mark on the ribbon cable itself,
as this marks pin 1 for you. And then, put the ribbon cable back the way you found it
later.
*******
There are at least three different ATX power supply specs. This one is for
a supply with a 20 pin main connector, and no -5V on the connector. Page 30
here, has a pinout. Connecting PS_ON# to COM (pin 14 to pin 13), will start
the power supply fan running and energize the main rails. Of course, there
is no need to do that, because your supply is already dead (we have already
given up hope). All that remains, is an optional post mortem if you're
interested.
http://www.formfactors.org/developer...X12V_1_3dg.pdf
I had a power supply go, that looked like this inside. My power supply
had four capacitors with the orangy/rust colored goo on the top of the
capacitor. Mine let out a little puff of smoke as well.
http://upload.wikimedia.org/wikipedi...4/PSU_Caps.jpg
If you take the lid off, you're allowed to look, but don't touch anything.
The main capacitor can be charged to 300VDC. It has a bleeder resistor
across it, to make it safe after a minute or two. But if the bleeder
resistor had failed for any reason, there is nothing to make it safe
any more. And thus the advice to not touch anything in there. Once you're
finished looking, you can discard it. Put the lid back on, before tossing it.
And *don't* attempt to discharge the main cap with a screwdriver. If there
was any energy stored in there, there would be a huge noise that could
deafen you. While folklore is to stick a screwdriver across the
terminals, you don't do that when the "total joules" is too big.
It's equivalent to making your own lightning bolt.
I lost my hearing in one ear for ten minutes, thanks to a capacitor.
The capacitor was in a microwave oven, an oven that was used at work
for popping microwave popcorn. Too much butter and salt collected
around the main capacitor terminals, leading to a very loud arc-over.
My right ear was facing the machine when I hit the Start button, and
the noise was so loud, I couldn't hear anything in that ear for ten
minutes. The cap in the ATX supply similarly has its share of joules
of energy stored inside. And I don't *ever* intend to test with a screwdriver,
to see how loud the ATX capacitor is :-( The microwave oven was enough
of a valuable experience, and I wasn't even playing with that one, just
trying to use it when it "went off". By the way, the capacitor in a microwave
oven is even more dangerous, and is charged to 5000 volts.
Paul
