Hello,

Having not posted for over 2 yrs, I hope I'm still welcome :-)

Anyway, on to the problem...

My friend's PC was not turning on at all, and, having experienced a similar problem myself, told them it was probably the power supply. They asked me if they could bring round said computer, plus an older one, the idea being to swap the PSUs around.

So, I sat down, opened both computers and noticed that the wattage was too low on the old one, so I was about to give up when I realised it might be the power lead (call me Sherlock) they had brought with them so I could test it without having to unplug my PC.

I used their power lead to test out my guitar amp and, sure enough, it didn't turn on. I realised the problem and used the lead normally used for my guitar amp to test the newer PC with the newer PSU. It sprung in to life and I was feeling pleased with myself for about 2 seconds before it omitted a very loud bang and an unpleasant smell.

I still had the power supply resting on the case when I plugged the 'kettle lead' in.
The only place I'd plugged the internal cables in was on the motherboard.

I realise my stupidity in having exposed live electrical items everywhere and for not properly installing the PSU before testing it and am feeling quite embarrassed to say the least.

So my question is, what actually caused the explosion? Was it having the PSU resting on metal with the computer not properly done up? Or the wrong lead (13A fuse!!)? Will it happen again if I follow proper procedures (which I am, believe it or not, familiar with)?

And what's the potential damage? I'm hoping it's just the PSU as it's easily replaceable (when you do it properly).

I'm still pretty shaken up cos I was right next to the PC at the time so excuse me if I've gone on a bit.

Thank you,
rocker88

Having not posted for over 2 yrs, I hope I'm still welcome :-)

You're not! Go away! lol

A power supply simply resting on the case should be no different from being attached to the case with screws. So I suspect the supply was bad. As far as the potential damage, I am afraid it could be extensive.

Also, note that older Dell PSUs and motherboards were not wired in compliance with ATX Form Factor standards, and are not interchangeable with other supplies.

lol Nice to see a sense of humour around here :-)

That's just what I thought, I've seen other people test them before properly screwing them in...but then maybe they were doing something I wasn't...lol

Luckily it's not a Dell, I've heard about them changing pins around and stuff...the swines! lol

How extensive are we talking? New motherboard? Or blown capacitators? Obviously you can't tell me exactly without seeing it but if you could give me a rough idea that would be great.

Do you think the 13A fuse in the other 'kettle lead' could've done it? Don't know much about electricals but if it were due to that, it would be entirely my fault...!

Thank you very much for the quick reply and your expertise :-)

Edit - Sorry, despite saying 13A on the outside of the plug, a little bit of investigating (opening the plug...lol) revealed that it is indeed a 3A fuse inside...a whole 10A less! :-)

Not sure what you mean by "kettle lead". I would hate to speculate what might have happened. I would not want to speculate on the possible damage either but certainly, if a power supply goes bad, anything plugged into it could have been destroyed.

That said, the damage could have been isolated to the supply as well. You might want to get yourself a tester. Here's my canned text on them:

I use a FrozenCPU Ultimate PSU Tester for power supply (PSU) testing when I am away from home. It is not as good as a qualified technician testing the PSU under a "true" (realistic) load with an oscilloscope or power analyzer, but close. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you can better detect a "failing" PSU, or one barely within specified tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, not a true load. Alternatively, you can swap out the PSU with a known good one that meets the computer's power requirements.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This then requires poking (with some considerable force) two, hard and sharp, highly conductive, meter probes into the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it.

Sorry, by kettle lead I mean the three-holed one that plugs in to computers, amps, and kettles...I should have just said computer lead...sorry :-)

Well, since my last post, I've tried installing the other power supply and what happened is that the green light on the card-reader drive came on, so the power supply works. But the computer does not turn on. I've tried swapping the 'powersw' lead with a new one but to no avail. So I'm pretty sure that means the motherboard has blown?

I'll try a few other things but apart from that, it's not looking good.

Thank you very much for your help and time though, it's much appreciated

I've tried installing the other power supply and what happened is that the green light on the card-reader drive came on, so the power supply works.

No, that just means the +5Vsb standby voltage works. It does not problem the +12V or +3.3 volts works.

Ahhh, so there's still a chance that just a new power supply will fix things?

I've noticed that the (now blown up) power supply had an extra four holes/wires where it plugs in to the motherboard but this old one (which did work fine in the old computer) does not. Is there a reason for this and is this possibly why it is not working? Not enough power or something?

Sorry to keep bothering you like this, my next post will be my last, promise :-)

Thank you

Newer supplies support newer graphics cards, and more power hungry devices. Any extra, unused leads can just be tucked away.

Okay, so is it possible that the older power supply does not have enough power to boot the (much newer) computer?

That's my last post, like I promised :-)

So I just wanna say thank you v much for your help, time and advice. It's great to know there are still some people out there who like to help others! Living in England, you sometimes forget that! lol

Thanks again and good luck

rocker88!