I have no idea what the previous owner did to the machine. One screw on the heatsink was missing and it looked like there was no thermal paste at all.

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I bet he was screwing around and just did not know what he was doing or heard about the early macbook pros having too much and thought he would 'fix' his G4 as well. *disappointed rolleyes*

Although, I found if the startup button board isn't in the right spot the system LED will only light for a second and tye system will not even start. However this may be a loose connection or wire on that section itself. I did smell a bit of an electrical smell... But I could not track down where it was coming from. Would be a shame if the CPU burned up right in front of me.

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I am not sure how the front panel board is mounted on the MDDs but next time you have it out look to see if there is any metal contacting odd areas of it or wires poking around the wrong places. It sounds like a short.(if it completely dies right after)Look for damage to it's cable as well.

Oh, and Paralel. I had a 700MHz eMac here that was overheating with the stock paste...Well, it was not paste anymore. Took 10 mins to scrape that old crap off then put on some new stuff and it worked fine.