Powerbook G4 booting problems.

Ey Guys,

I got this Apple Powerbook G4, which has severe booting problems. So badly, that it won't even show any BIOS screen or POST messages. The screen remains black. It already has problems with the PSU, but I get it to run it's vents with it plugged into a power source. If not, it won't respond at all. Does this have to do with the PSU, or maybe the HDD? I was thinking about the CPU or RAM, that malfunctions, but I want to know more before I open it up.

Thanks in advance!