Power issues

[AlphaTrinity]

Hey guys,
I'm working on a friend's computer trouble right now. I haven't worked with the computer directly, just by what he's telling me.

He says that his computer will just shut down at random times (when gaming and when it is idle), but it will not shut down completely; fans will still be spinning and certain leds will be glowing.

My first thought was a power supply issue. I haven't asked him what brand or model his power supply is because I figured that wasn't important right now. I wanted to ask if you guys knew a good software tool to use to test those 3.3v, 5v, etc. Sorry, I haven't really dealt with power supplies very much so far, so I don't know exactly what I'm talking about here, I just remember often reading that if those numbers are too far off (either high or low) that means that it is a bad power supply and/or a dying power supply.

Specs about his computer that I do know: It's an MSI AM2 board, he was running an 8800gts I believe, but will use his old 6600 to test since that draws way less power. I believe his CPU is around a 4000+ or 4200+ (not overclocked) and like I said I am not sure what his power supply is at the moment. He has been running this computer for over a year now, and he said that just in the past two weeks he's been having troubles.

Thanks a lot for any assistance! :)

[Qeldroma]

You might see if MSI has a utiltiy that can read the voltages off its motherboard. Some manufacturers package one with the mobo install CD. Of course, there is the old tried and true- a voltmeter.

However, messing with a potentially funky PSU is usually not a good way to go- I think it risks another component with flakey power transients. If you suspect it's clipping out (which this sounds like), I'd just grab another PSU (of greater rating) and try it out- at the very worst, it doesn't hurt to have a spare one around.

[Leonardo]

Those are classic symptoms of an inadequate or malfunctioning PSU. It does not prove it's the PSU, as the problem could also be motherboard. But it's a 9 out of ten chance it's the PSU. Wanna bet he's got a POS PSU in his computer?

[AlphaTrinity]

Okay so PSU it is.

When we talked some more he told me that he just reorganized his computer a bit to add some cathodes. When he mentioned that he put the cathodes on the same rail as his video card a red flag popped up. I told him to put the card on its own rail. He did that and now everything is running great.

Is the PSU still bad and should be replaced even if it is now running perfectly?

EDIT: Oh yeah, I had him get that MSI utility and he said everything was pretty close to what it should have been. I told him it's normal for the readings to be a little off, so he guessed that everything was fine.

[Leonardo]

If his computer is working fine now, then his PSU should be adequate. To me it would appear that the PSU is a low power, marginal unit (probably el cheapo to the max). Cathodes don't draw that much power, so it seems the PSU was right at the overload level before. If it's that close to overload, he should upgrade his PSU if he plans for more computer components to be added.

Ask him what brand and model of PSU he's running.

[Qeldroma]

If you can give further specs on his PC, that'd be good too.