My ATX PSU looks dead – was it murdered or is it natural causes?

LucianH

My desktop is currently lying in the middle of the floor with its legs in the air. It appears to be dead (of doing a very good impression). It looks like the PSU but before I go and get a new one I would greatly appreciate the deductive powers of you wise folks.

Current symptoms are that the PSU is no-more (Tagan TG480-U01). There’s definitely 240 volts going in (checked with meter) and there’s no sign of any output on either the ATX Power or the +12V connectors (I’m assuming I should be seeing only the +5V standby on pin 9).

The sequence of events that led up to this is that the PC did not shut down properly last night (Windows XP by the way). Just before shutting down, the User had been switched but it reported that there was insufficient something or other and that it would load a reduced profile (this is a secondhand report from a reliable witness). A shutdown was then attempted which appeared to work (monitors switching off) but the base unit was still sitting there whirring away. This led to the final resort of switching it off at the socket… And now it is lifeless.

So before I go out and get a new PSU – does anybody think that there could be possibly something else that’s screwed up with the PC that could have damaged the PSU? I know it’s probably unlikely but I’d hate to fit a new one only to find that it then subsequently dies.

macman

If you've tested the output and it's zilch, that's fairly conclusive evidence of PSU failure. Sometimes sudden PSU failure can fry PC components, not the other way around.

LucianH

macman wrote: »

If you've tested the output and it's zilch, that's fairly conclusive evidence of PSU failure. Sometimes sudden PSU failure can fry PC components, not the other way around.

Am I correct in thinking that the 5V standby is the only power I should be seeing? And the PS_ON (pin 14) is the control that switches on the PSU output? (is it shorted to ground to enable?)

macman

Sorry, no idea, I just use a PSU tester, if the green light doesn't work then it's replaced
At £20 for a basic PSU then it's not worth spending to much time on analysing it.

kingshouse

macman wrote: »

Sorry, no idea, I just use a PSU tester, if the green light doesn't work then it's replaced
At £20 for a basic PSU then it's not worth spending to much time on analysing it.

I would never buy a £20 PSU, you are asking for trouble, get a good quality PSU.

macman

That totally depends on the PC. I changed one recently on a low-spec 7 year old PC that was probably worth £50 at most. Would you really spend more than the PC is worth to fit a 'quality' brand PSU?
Yes, a £50 one will run a bit quieter and certainly last longer, but even a £20 one will last longer than that PC is likely to.

GunJack

look around, get a cheapie PSU for around £12, if it fixes the pc - great, if not, it's only £12 and 10 mins of your time. If it does fix it, then you could splash out a bit more on a "better" psu if you really wanted to

DodgyMoney

My experience of cheap PSUs (working in a computer repair shop for 5 years in a previous life) is that they're not worth the risk. So many go bang a month outside of warranty and take half the PC's components with it.

cit_k

I have only ever had on PSU go bang, and that was a expensive one.