Backlighting at zero brightness during boot or single-user mode

As of a few days ago, my PowerBook G4 (15", 1.67ghz) running Mac OS 10.4.8, has developed an odd screen brightness problem. When I turn it on, the screen backlighting stays off during the gray apple screen. It only turns on when the computer gets to the "Mac OS X" screen with the progress bar. At first I thought the computer simply wasn't coming on, but I happened to catch the screen at an angle in bright light and saw the little Apple logo in the center.

Unfortunately, the backlighting stays off when I boot into single user command-line mode, so I can't see anything I type there. It's weird.

There have been a few changes to the system in the last week. Most notably, last Thursday it had its hard drive replaced by a technician... the original one died on me (hard clicking and grinding noises, lost all data, thankfully had a recent backup). I reinstalled 10.4.2 from the installer disks and upgraded via Software Update control panel. And now I have this brightness issue.

Once the computer is up and running, the brightness controls are fine, and the brightness buttons (F1 and F2) work as intended.

Any ideas how to restore my startup backlighting?

PowerBook G4, 15", 1.67ghz Mac OS X (10.4.8)

Posted on Jan 9, 2007 6:12 PM

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1 reply

Jan 10, 2007 3:47 PM in response to Tor de Vries

With the help of an Apple IT friend, I've been able to fix this. The solution was to delete the following files...

/System/Library/Extensions.kextcache
/System/Library/Caches/com.apple.kernelcaches/* (e.g. every file in this folder)

...then reboot the system. Works fine now. Thanks Jon!

(FYI, you need the administrator password to delete these files.)

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Backlighting at zero brightness during boot or single-user mode

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