Power Mac G5 Won't Turn On

I recently purchased a Power Mac G5 Dual 2GHz from ebay. I tested the computer a couple of weeks ago when I first got it, but wasn't able to actually set it up with all of my music gear until last night. I installed Logic Studio and a driver for my firewire audio interface and started downloading all of the updates. While downloading the updates the computer just turned off. I wasn't in the room, but when I came back in it was totally off. I tried to turn it back on by using the power button in the front and it won't turn on. It clicks once then clicks again a few seconds later, but no light and no power. Everything else that is plugged into the same power strip turns on. I reset the PMU, and even the graphics card just to make sure. I still get nothing. I have exhausted apples support page, and I don't know what else to do. Please let me know if you have any helpful ideas. Thank you, Andy

Some time Andy the power supply unit just go's its a common fault with that model, if its that, it may still be under warranty, thats if your lucky.

It looks like you on your way to a main dealer mate to have it checked.

Does the powerlight briefly come on before fading out

No power light at all, nothing happens except the faint clicking sound.

Yeah, mine done that once after I spent 45 minutes cleaning it. Scared the living daylights out of me!

I removed all the cards, fans and ensured all connectors were tight and it booted right up.

The clicking noise is definitely the PSU though and is normal on every cold start, but I guess something in the PSU has blown.
If you have access to compressed air you could try blasting the lower area of the case, I was amazed how much dust/fluff blew out mine.

I would try using a volt/amp meter on its outputs to see if it is truly dead first