Where are the guilty, leaking caps?In my experience, passive matrix screens can have leaked caps, causing screen issues such as a faint display/occasional "yellow-out" issues. I had it happen to a PowerBook 140 and a PowerBook 160.
It is stupidly easy in the displays in the 1xx series.Like, mars478 could do it.. though he might break the lamp later.. but meh. heheI'd imagine very very old LCDs couldn't be any harder.
I have a 190 like that. On mine, there is a bad connection between the printed ribbon cable and the actual LCD. I found this by touching and wiggling various parts. A possible solution is to wedge something in there that keeps pressure on the affected area.I have two 150's here that have entire sections of the screens dead. They partially work, but those dead areas make it impossible to really use them.