Weird display issue with Powerbook 520

everett1911

macrumors member
Original poster
Aug 4, 2017
39
15
Montreal, Canada
I have a Powerbook 520 (the one with the b/w monitor) and there's this weird issue with the display where when I boot it the monitor will always be at max contrast and brightness, and even after adjusting the contrast it'll slowly drift and change on its own. Is there something I can do to fix this?
 

MacTech68

macrumors 68020
Mar 16, 2008
2,185
149
Australia, Perth
According to the 'User Guide':

"When you first turn on your computer, it may take several minutes for the
screen brightness to “warm up,” especially if you’ve chosen a high setting."


Note that ambient temperature changes will also affect these older LCDs. In that respect, it's normal.

Also, those old FSTN displays were pretty terrible. That aside, I wonder if your PRAM/'Backup Battery' is flat or failed.

To test that, set the date & time, then shutdown and unplug the mains power AND any user-removable batteries for about 10 minutes. Then plug in the mains power and power on. If the date has reset to default (1972 ?) then you need to leave it connected to the mains power for 48hrs and re-test. If it fails again, you need a new internal backup battery (or you can just live with it).

It's possible that the LCD display or the interconnect board or inverter board (all located within the display housing) has a fault.

Finally, if you haven't already, do yourself a favor and google "powerbook_500_series.pdf" :)
 

MacTech68

macrumors 68020
Mar 16, 2008
2,185
149
Australia, Perth
If you're good with fiddly, tedious, little things that require a lot of patience and diligence and you have good soldering skills then sure. The more experience the better. I've not rebuilt one of these LCDs before. Some are relatively easy, and some are fraught with dangers.

As for the battery, no, highly unlikely. They can be rebuilt but require a lot of care, and probably replacement of the eeprom (93c66) which is re-programmed by "Intelligent Battery Recondition". It will ask for the serial number prefix (BP prefix is Panasonic cells and BS is Sony cells) and program the IC appropriately.