Ibook G4 Flickering/Brightness Change problem?

I have a G4 ibook. The screen keeps shutting off the back light randomly. I changed the inverter board and cable and it worked fine, but i noticed that the screen brightness wasn't turned all the way up. When i turned it up the screen shuts flickers and it sounds like the cdrom keeps ejecting than the creen comes back up. when i turn the brightness back down it works again. could it be a power issue or motherboard?