PSU Troubleshooting?

[pcgamer4life]

I've got a PSU that's about 18 months old. It's a mediocre (at best) unit, an Aspire ATX-AS550W-BK. It died on a friend, so I replaced it for him and kept this one just to troubleshoot what went wrong.

I cracked open the case, and don't see any visible burns, bulging caps, or anything, though it is incredibly dusty.

My question is, what are some common issues with PSU's just dropping dead, and how might I go about troubleshooting them?

Thanks!

[larrymoencurly]

Fan fails and makes PSU overheat.

Bad solder joints, either from bad cleaning of the leads at the factory or a crack from shipping. Cracks can sometimes be microscopic, so start by resoldering the heavy parts, like the transformers, but be careful not to disturb any surface mount parts.

Diode or transistor shorts out. Use diode check or ohms function of meter to pinpoint. If the fuse blew, suspect parts on the high voltage side.

Capacitor or transistor in +5V standby circuit fails.

Usually, a capacitor failing elsewhere won't cause sudden total failure.

[EarthDog]

Aspire? Thats a good unit to practice on for repairing a PSU. Oustside of that it has zero value as they are POS PSU's