ALL of them are bad? On mine only the orange Rubycons (Fake ones) are dead.In that lot of iMac's you got do you happen to have a good PS? I would buy one from you.

Click to expand...

All 4 have bulging/burst capacitors in the power supply, even the one that still powers up OK.

This person suggests changing out all of the failure-prone parts, not just the one or two that are obviously shot:

http://jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php