A short circuit, dead component of some sort, what next?

Hi All,

I'll try to explain the background to this issue as concisely as possible

Mother-in-law's computer had a virus, so we gave her one of ours that was not being used while I fixed hers. While she had it she tried to update Live Messenger, but it froze doing so. Rather than switching it off by holding in the "Soft-off/on" button on the front of the PC, she switched it off using the switch at the back of the Power Supply Unit! :pfff: When she tried switching it back on it may or may not have made a pop noise, and of course it now does not power on, no sign of life at all.

My initial thought was she killed the PSU. I unplugged all leads from the suspected dead PSU and connected in a spare known-to-be-working power supply ~~ I had only used this spare the previous day to diagnose a friend's dead PSU in their PC, which worked so we went out and bought a new one and fitted it to their PC, all happy, but I digress...

Once I had the spare connected, I plugged it in to mains power and turned on the power to the PSU all looking good - the blue light and the fan in the PSU are going as well as the fan in the case. I press the power button to turn on the PC, immediately there is not so quiet BANG, a spark and a burning smell coming from the spare PSU. I immediately remove the mains plug and switch of the PSU. I disconnected the PSU from the PC and tried plugging in to mains and switching it on - completely dead now :(

It would appear something in the PC has fried the PSU, I'm afraid to connect another PSU, lest I fry that one too.

What further troubleshooting steps should I take to work out what is causing this, or am I better off junking the whole thing to be on the safe side? It was a PC I built back in 2005, so not exactly worth much by today's standards, but still I can't exactly afford to go out and buy a new one to replace it at the moment.

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  1. Hmm. A 'new' computer would cost very little these days, which I'd say would probably be the best option.

    AMD Sempron 140 2.7GHz - $36.99
    MSI 760GM-E51 - $69.99
    Crucial 1GB DDR3 1066MHz RAM - $29.99

    Total = $136.97

    Note that the motherboard has integrated ATi Radeon HD 3000 DX10 graphics - not very powerful at all, but more than capable of helping decode HD video and for basic web games or web surfing. Vista and 7 Aero is supported too, if you like eye candy.

    Also, I'm supposing you could the old case (as long as it supports microatx motherboards), hard drive (the mobo has one IDE port, enough for one IDE DVD drive and HDD), DVD drive, monitor, mouse/keyboard and that other PSU you were afraid to test.

    If you don't want to pay for a new computer, I'd just check that the standoffs are properly mounted, graphics card and RAM are seated, and that everything is connected properly - otherwise, it could possibly be that the PSUs have died, the system might use two much power.
  2. ^^ well said.

    What are your system specs? Can you tell us the brand, model and power of the PSUs you tried?
  3. enzo matrix said:
    ^^ well said.

    What are your system specs? Can you tell us the brand, model and power of the PSUs you tried?

    Thanks for the replies thus far.

    I can't remember specs off-hand but I'll see if I can track down the invoice of the parts tonight, as it was a system I built myself.

    Basically though, it has a single HDD, 2 DVD drives and a Graphics card. Both PSUs (the suspected dead one and the one that died from the attempted test) were both 500 Watt PSUs, the one I was testing with was newer, more expensive, better quality and not had nearly as much use.

    As I said, the testing PSU worked fine the previous day for testing another PC, it just seems highly unlikely for the PSU to suddenly die like that. It's light and fan were on and it was sending power to the motherboard (the mobo light was on). It was only when I pressed the power button to fire up the PC that it went bang.

    The problem is, without knowing what caused the PSU failure (maybe it was just the PSU), can't just simply buy replacement CPU, Mobo, and RAM. Could it even have been caused by a problem with the computer case itself, or any other component for that matter? In that case, that would need to be replaced and not everything else. This is where I'm stuck! :) I don't have the knowledge/expertise to test these components, but I'm reluctant to junk the entire system on the off-chance that it is only a single failed component that in turn destroyed the PSU, that needs to be replaced.

    Is it even possible for a component to somehow destroy the PSU? Guess it could be human error too, but it wouldn't be too easy to plug in a PSU incorrectly, plus I've removed/installed PSUs near to a dozen times now.

  4. Most likely the PSU just died. Generic? Wattage means nothing if its not name brand.

    If theres a Frys in your area they have instore specials every Monday, Wednesday, and Friday. You can get a quad core and motherboard for $100. Usually on Fridays.
  5. Thanks daship, I thought it unlikely too that a component could fry a PSU. Never experienced it before scared the crap outta me. Then you start doubting yourself - "bloody hell I maybe I did something wrong!" despite checking it over a few times before plugging in and switching on power.

    I might take it down to where I purchased the parts - they do repairs too, see what they think about it. Have never heard of Frys so they probably don't exist in Australia. :)

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