will power up, but has black screen

What model iBook G3 do you have? Is it a white iBook with a processor between 700MHZ - 900MHZ? If so, and there is no faint image on the screen, you likely have the very common G3 video issue, which often presents the symptom you mention. Try powering on while clamping the machine with your hand just to the left of the trackpad, pressing from top and bottom with a significant amount of pressure (but not enough that you squeeze the hard drive). If the screen comes on with pressure applied, you've got the video issue. If this is the problem, you can read some of my previous posts concerning what can be done to relieve the issue (although, unfortunately, most fixes are not permanent, and the only permanent fix is not cost-effective considering G3s have very little monetary value at this point).