My iMac G4 all of sudden refuses to start up. Push the power button, nothing. No fans, chime nada. I reset the PMU button, it booted, then the next day same thing. I took it apart, checked the RAM, and even replaced the PRAM battery. Now it actually powers up one out of maybe 10 times, sometimes chimes but the screen stays black, every once and a while makes it all the way to the desktop, sometimes KPs. Haven't been able to check the log since it won't put consistently at all. Any chance this is power supply? Or best bet logic board? Thanks!