The screen on my G3 Bronze laptop (10.3.9) has turned extremely dark gray. Maxing the brightness function doesn't change it. Is there anything I can do?
If you have actually tried calibrating the display - not clear, as you only mention that your settings appear correct - then your backlight is failing, or already has failed.
The backlight bulbs deteriorate over time. Not really the screen itself. Some backlights are fairly simple to replace, others require replacement of the screen, which is never a cheap repair.
If you want to try a repair, google for 'powerbook display repairs', or 'powerbook backlight repairs', and check out some of the choices that you get.