Something very worrying has just happened. The computer sparked when I plugged in a USB mp3 player and the computer turned off. This was followed by a burning smell which im pretty sure came from the 350w PSU. Is this because the PSU has been overloaded or can anyone give me an idea of what is wrong. The hardware is as follows:
2400+ Sempron not overclocked
Radeon 9250se graphics
512mb ddr ram
20gb maxtor HD
Floppy drive
DVD/RW drive
Athlon XP 2500+ stock cooler
I had a problem like this before the usb shorted the computer luckly the power supply did not cook and I just removed said usb plugs and it was a happy bunny…
have you checked all the caps inside the computer ? on the motherboard ?
if you can smell the back end of the power supply to see if it smells !!
yeah it smells like something inside the PSU has cooked.
two processors ? 
DT.
No just the one, im thinking maybe a bigger PSU is needed?
cannot see anything that would overflow that power supply 350w is ample with that setup…
but yes could be that it died from the shorting…if u can borrow another power supply from somewhere then maybe do that just to check 
I’ll have to rip out the PSU from my main rig then 
Even if that is the problem, why would the USB short the computer.
Are you sure you did not flick the little red switch on the back of the PSU?.
if not then sounds like it either have been too old and the dust caused it to go POOF! or yes it could have been over loaded with all your stuff including the CPU that cant decide to be a sempron or athlon 
Well i definetely didnt flick the red switch and I built the system less than 3 months ago from all new parts.
Don’t quote me on this but I don’t think the USB shorting can cause a PSU failure due to the nature of the USB circuit and running a limited current.
If anything your likely to burn out an IC but not cause direct power to be shunted to ground.
Could just be unlucky timing, don’t know what your PSU brand is but not all PSU’s are made equal and Qtec are good examples of a PSU to avoid where there rated power and actual ability are like chalk and cheese.
In essance what I’m say is your could have a 350w PSU but it could be just as
good as a 200w PSU depending on branding and build quality.
When you say you built it yourself, did you use all the board standoffs etc – no chance of the
motherboard contacting the case in anyway and shorting that way.
I couldnt use the washers supplied because the case already has raised platforms and the washers would have meant the backplate wouldnt have fitted. I would have thought that having raised points in the case must be as good as using the washers or am I wrong?
Should be ok as that’s quite normal, but sometimes you don’t get the
full compliment which can mean a large portion of the board hanging
over the last raisers at the back of the board and sometimes the flex in the
board at the ATX connector can be a little too close for comfort.
– Just mentioned as a possibility and something to keep an eye out for
on the off chance.
I know this is a silly one but did you use the spacers as is ? or repositioned
to suit the board in question ? possibility of a unused raiser in the wrong position making contact with part of the board it should not.
Alot of senarios to be honest but alway’s worth while checking what you can
just in case.
every one who “home builds” pc’s, in my opinion should have one of these or another variant, well worth every penny the one I have, saved me hours looking for faults in machines.
DT.
Another problem now. Used a different lead (the one i use to power my main rig) to power the ‘faulty’ PSU. I heard another crack/spark and the lead stopped working, is this a blown fuse or has this lead died too
Fuse will have gone on the lead, just replace with same.
Does sound like the PSU is royally fubared though.
So i need to change the PSU but what can I do to make sure this doesnt happen with the next one.
I’ve got every set of machines running off some form of UPS, looks like you missed out on the bargain price that these were at, I got two for £45.23 a short while ago
DT.
It’s never fun when the Mystic Black Smoke that makes it work, gets out…
my psu always die from Ballbaring Collapse… lucky me hay?
Ok then, i tried another PSU and the system boots up so it must be that. After removing the faulty PSU though, i found a rather nasty dent in its underside. God knows how it got there but i think its possible that it may have made contact with the soldering on the board inside. I removed the casing (i know its a big no-no but i was curious and wanted to salvage some screws) and I didn’t find any markings of burning or any melting. Anyway, the new PSU should arrive by Friday so I get my secondary cruncher back.
Now to make sure the USB points dont spark again… I’m going to pull apart the system, check for shortages, clear any dust and pray that this doesn’t happen again. Did I mention btw that the spark came from between the USB port and device being plugged in. These are two separate devices and two different ports. I still don’t fully understand it