When you press F8, F9 or F10 on your PowerBook G4 (17-inch) or PowerBook G4 (15-inch FW 800) computer to change the keyboard illumination settings, you may see a prohibitory sign., as seen in Figure 1.
Figure 1 Prohibitory Sign Seen When Pressing F8, F9 or F10
Solution
If you see the dimmed graphic with the prohibitory sign when attempting to change the keyboard illumination settings, the sensed ambient light is not low enough for the keyboard illumination to be active.
Keyboard illumination cannot be adjusted until it is active. To adjust the keyboard illumination, take the computer into an environment that is dark enough to activate the feature. Then use the F8, F9 and F10 keys to make adjustments. For more information on this feature, see technical document 86270, "PowerBook G4 (17-inch), (15-inch FW 800): How to Deactivate Ambient Light Sensor (ALS) Automatic Brightness Adjustment".
Note: Not all PowerBook G4 (15-inch FW 800) models include the backlit keyboard and ambient light sensor. To determine if your model includes these features see if the F8, F9, and F10 keys have the ambient light sensor icons printed on them.
Figure 1 F8, F9 and F10 keys on keyboard
If these icons are not printed on the keys, then these features are not present in your model.