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I knwo this sounds QUITE crazy (not for the techies though). I had a Chieftec 450W PSU which died after I "transported it" to my friend so he can use it afterwards. (Bought a new PSU so I didn't need the old Chieftec.)

When I assembled his PC with the new PSU, only the CPU cooling and the VGA cooling started. No PC speaker noise, no screen, and the PSU fan was dead. When I checked the PSU fan (removing the bottom metal cover), it was dead. (Not moving, totally burnt.)

The PSU when I last used it, WORKED PERFECTLY.
I just turned my PC off (I used it just before I replaced it with my new one).

My friend is really poor. He wants to repair the PSU. How should I start?
If ONLY the fan would be dead, I think we'd have some VGA output too (until the PSU overheats.. but the PC was only running for a few seconds.)

Multimeter and check the voltage?
And one huge note: When I plugged the PSU in after the assembly, there was a noise at the cable's end.. you know that zzzz-zzzz (can't really explain it with words, but the usual electric buzz which tells you to get the .... out as fast as you can. :))
(Of course if I try to run the PSU , I'll use a fan to keep it cool!)

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Perhaps the main reason not to do this is the fire risk. Most computer parts are low-voltage and very unlikely to catch fire, but a 450W PSU is a different beast. – MSalters May 31 '11 at 12:08
possible duplicate of Could I replace a stock PSU fan with a more quiet one? – Nifle May 31 '11 at 12:12
@Nifle: Yeah but that's only the fan. There may be some other problems too. – Shiki May 31 '11 at 12:47
It goes without saying to use a circuit breaker if you are going to go anywhere near the psu insides, otherwise odds are that bad things will happen involving your hair style. even then, psu's are so cheap it just isn't worth the risk or effort. – Sirex May 31 '11 at 14:47
up vote 2 down vote accepted

I've attempted this. I'd say its not worth the effort, is dangerous and generally a bad idea. If you DO decide to do it, its a simple matter of checking continuity to the fan's leads (multimeter at the two places where the fan is soldered to the board... if that fails check along those traces)(optionally) to make sure nothing else burnt out, getting a fan of the same size, and wireing it up appropriately

However there's 240V in there, so do NOT work on the PSU with the cover off, and make sure there's no shorts at all. It wasn't lethal to me but could be, and it hurts like hell if you get shocked.

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What 240V can do to you: – RedGrittyBrick May 31 '11 at 14:21
edited to reflect potential lethality in addition to prospect of pain. – Journeyman Geek May 31 '11 at 14:34
There's HIGH VOLTAGE DC in there. VERY nasty stuff. – Linker3000 May 31 '11 at 14:35

It sounds like the fan blowing is just a symptom of the real and worse problem. Like you said, if it was just the fan, it should have worked as long as it didn't overheat. I'd say remove the fan and check the voltage of all of the outputs because it is quite possible that the regulator failed and the reason the fan blew is because it was being fed too much voltage. This means it's also going to smoke your other components too.

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