Debugging an ATX power supply.

[westfw]

I have an ATX power supply that has gone "wonky."  The computer it powers will run for about 5 minutes when first turned on, and then goes into a loop where it powers down and starts up again, not quite lasting long enough to boot.
It seems like it's likely to be a classic "bad capacitor" problem.  (replacing the Supply fixed the computer that it was in.)

Any hints on how I can narrow that down to WHICH capacitors I should try to replace?  Unfortunately, there isn't any obvious bulging or leaking.

[bob91343]

Schematic diagrams are available online.

[darkstar49]

facing similar issue with an oscilloscope power supply (other thread...), but if it uns for 5+ minutes first, I'd rather suspect a thermal-related issue.
If I got it right, when you let it cool down, you're good for another 5 minutes, correct ??

If yes, I'd be really surprised if one of the electrolytics was the problem... keep us posted !!

[PKTKS]

Most of the time a generic rule of thumb in these cases...

- If one capacitor is already presenting problems (dry.. heat.. bad manuf.)
 => replace them ALL  or just in case ALL from same brand or model

- The ALL case is not cheap - the cheapest thing to do is replace ONLY ONE

- If ONE CAPACITOR is faulty you may have luck to spot them visually
OR... by using LCR techniques in which removing them (and discharging)
for testing is the best method.

I my personal opinion if would remove anything ... I rather replace it.

Paul

[westfw]

when you let it cool down, you're good for another 5 minutes, correct ??

Yep.  Could still be the caps, though.  I haven't quite decided that it's worth fiddling with; after all, new computer ATX power supplies are very cheap...

[Haenk]

The ATX supplies are really cheap nowadays, buying a working used one is probably aven cheaper. Even cheaper than the replacement parts
And don't use it with your computer, when the PSU starts to act up, evil things like voltage spikes might happen. Which are obviously not a good thing for sensitve computer parts.