Hi guys
 
I have an Antec Tru Power II 550w.
 
Several months ago the pc would not fire up at all - no fans, no POST nada. A flick of the switch at the back of the case and/or plug socket seemed to solve the problem. However, it started creeping in more frequently.
 
I convinced myself at the time (read that as meaning I was finding an excuse!!!) that it must have been mobo related and treated myself to a healthy upgrade (board, C2D and RAM) and kept the PSU.
 
I've been running the new set up for a couple of months with no hiccups but recently I noticed a return of the old symptom again. Again, a flick of the switch and waiting 10 seconds seemed to cure it.
 
Is my PSU at fault and is it on the way out? Everything is rock solid and stable once the things fires up. The connections to the on/off button to my Antec P180 case seem fine also. I thought it might be some sort of safety device for fluctuating power surges or something, fitted within the PSU but can't find any reference to these things being fitted with such things so that's probably rubbish. But what do you guys think?
 
I don't mind buying a new one (I'm going to be replacing my 7800gtx soon anyway and so may benefit from more juice) but don't want to for the sake of it.

Probably not... PSU dying you'll start seeing shutdowns at random

that's what I hoped - any ideas what may be causing it?

You have it plugged up to a wall or surge protector?

not using a surge protector, its plugged in via a triple plug extension. Do PSUs have them built in - could that be it?

Welll even if this isn't the cause, I definitely recommend plugging into a surge protecter "Your computer can still recieve random surges that can damage it even when turned off" from the book Upgrading Your PC for Idiots

Your PSU has various built in circuit protections. If it is not happy with the voltage it is getting from the wall, it will shut itself off to "protect" itself and your computer. If you are comfortable using a volt meter, you might check the voltage coming from the wall.
 
The surge protector is also a good idea. A good quality one, not  $5 Walmart special. Triplite makes some good ones in the $15-$20 range.

thanks. Would it in the meantime be better practice for me to plug it straight in to the wall rather than via the extension lead then?

NO!!!!!!!!!!!!!!!!!!!
Put it in a surge protector.....Better yet if you don't mind spending the extra cash buy a U.P.S...(Uninteruptable Power Supply). It will filter and smooth out the spikes and drops so you'll have a constant 115V.AC.
I have one and I've never had an issue with power since.....

ok thanks for the advice. Presumably then you don't think there is the need to replace the PSU?