IMAC EMC 2211 won't turn on, already replaced power supply

Hi all,

I just replaced my power supply on my early 2008 model iMAC EMC 2211 because I figured with my small amount of experience that the power supply was bad....all 4 of the diagnostic LED's do NOT light up. I tried different power cords etc. Everything was working fine, then one day it took a few tries to get it to turn on and then about a week later, I tried to turn it on and it doesn't respond to the power button at all.

Can I test to see if the new power supply I bought it also faulty? It's a new part #661-4478, so I don't think that's the problem...but maybe.

What are the chances that the switch isn't allowing power to get to the power supply?

Any other suggestions? My MAC service guys can't get to it for a month.

Thanks!