I finally decided to refurbish a 15" iMac G4 i had in the basement from when i worked K-12. Got a new power lead and some new ram (no ram installed). Machine booted up in 9.2.2. Ran hard drive test on boot and passed. It loaded all extensions, got to the deskto pand hung (wrist watch mouse pointer). A few minutes later (2-4 minutes) it shuts off. Now i get nothing. no fan spin, not click, nada.... PRAM battery is also new. I followed the service manual checks and the PSU is putting out 12v at all the right spots and cap C189/197 both show 12v at the postive terminals. Power button also checks good.
Any other ideas?