Issue
When using system software older than 7.5.5 on a PowerBook 500 series computer with the PowerPC upgrade, the Display Brightness control push button does not work unless AC power is connected.
If you adjust the brightness or contrast while the unit is starting up, and running from the battery, those controls will become locked in at the current brightness/contrast setting.
Workaround
Do not adjust brightness or contrast until the unit fully comes up to the desktop. If you wait until the computer is finished starting up to make adjustments, the brightness and contrast buttons will work normally.
Resolution
System Software 7.5.5
System Software 7.5.2 v 1.2 is the version of system software which originally shipped with the PowerBook 500 series computer PowerPC upgrade. Installing System Software version 7.5.5 fixes display brightness issue.
Alternate Solution
Newer Technology has created a system extension that corrects this issue. It is called NUpowr Backlight Fix.
This article provides information about a non-Apple product. Apple Computer, Inc. is not responsible for its content. Please contact the vendor for additional information.
The following Tech Info Library article can help you search for a particular vendor's address and phone number:
Article 17159: "
Locating Vendor Information"
This article was published in the Information Alley on 27 June 1996. It was published again in the Information Alley on 8 October 1996 with updated information.