What capacitors typically are faulty in the 2010 MC508LL/A PSU?

I have an iMac 21.5" model MC508LL/A and only the first diagnostic light is on. When I hit the power button, the diagnostic light goes off and stays off unless I unplug the computer and plug it back in. From research, this sounds like I am in need of a new power supply unit. I've extracted the power supply and don't see any bulging capacitors, but know this isn't a definitive indicator of a faulty capacitor. So, I'm asking for help. Has anyone seen routine failure of certain capacitors on this PSU? I'd like to solder in a new one and save myself some money. Also, if someone has a different idea as to what might be wrong, I'd appreciate the input.

Here's to fixing it yourself.

Cheers,

-Liam