[nixgeek]

My father had an issue with his Power Mac G5 1.6 where you could tell it was on, but nothing would come up. It would eventually have the fans running full-on. I suspected one of three things: failed PSU, failed logic board, failed CPU. Quite possibly, even a combination of these was possible. We took it into the Apple Store at one point and we were told that we had to replace the CPU, which at the time cost about as much as the machine was worth when this happened. I didn't have him repair it because well, this was told to me by an Apple Genius. We never got around to taking it to another certified Apple repair center as he eventually got a used Power Mac G4 dual 867, but it might be something for you to consider at this point. Try the Genius Bar at the Apple Store, and if you're not too pleased with the response take it into a certified Apple service center where you feel that the techs are actually of the technical nature.