Black screen when powering on PowerBook

Hi,

I recently acquired a Powerbook G4. Whenever I go to turn it on, I hear the chime, the DVD drive makes a noise and then nothing happens - the fans don’t start, the hard drive doesn’t spin up, and the screen stays black, but it is still on. I’ve tried resetting the PRAM but it didn’t work, anyone have any ideas? Is it the PRAM battery? The caps lock light won’t come on either, I’ve tried two different keyboards.

Many thanks