Last week we reported on an issue where horizontal lines appear on PowerBook screens, possibly due to logic board issues. We've since received a number of confirming reports, affecting a variety of portable models.
Rodrigo Martinez presents a strange scenario where his PowerBook only exhibits the horizontal line problem when Apple System Profiler shows the correct amount of VRAM:
"I am also having problems with my Powerbook. It was the latest of the Ti models with 64 MB VRAM. The problem is now my Powerbook is only showing 32 MB VRAM (through Apple System Profiler, what the 867 MHz model had) and under this "bizarre" condition it actually works quite well. Unfortunately every once in a while the 64 MB VRAM show up, but the screen gets strange horizontal lines. It still works, but the screen gets messed up and ugly."
For some users, the problem only occurs when certain -- usually processor or memory intensive -- applications are used. Mike Acevedo writes:
"I have had this problem on my 1Ghz TiBook with 1GB of RAM. It has been this way since about January. I will send it off to Apple soon to see if they can repair it. I hope it's an issue that doesn't arise again, because it's pretty annoying trying to produce tracks in Garageband or edit in Final Cut Pro, and it just goes haywire. I gave a keynote presentation with it and had the powerbook connected to a projector. I had my display mirrored, and lo and behold, those lines started going haywire, but the projected image was fine."
MacFixIt reader "W" had a similar experience with the issue, with processor intensive operations triggering the issue:
"I have a rev 2 TiBook and am relieved to see that others are having the same flickering/lines when the computer heats up. My screen flickers, it seems, during periods of high CPU use. It took me a while to figure this out, but for some reason, certain Flash web-presentations especially cause the screen to go bonkers, as if there were a loose connection somewhere. Another operation that causes the screen to flash is unzipping a file or playing an large media file in VLC."
For others, the issue occurs during DVD playback. Sean Field's experience:
"I was travelling to NY in January, and while on the plane, watching a DVD, my screen went blank. Upon closing the lid and reopening, I began to notice the screen with lines across it. Thinking this was some sort of glitch, I put away the laptop to wait til I was on solid ground to look into. Upon arriving at my destination, I was shocked to see the system still with the lines.
"The next day off I went to the Apple Store in NY, where I spent a few hours waiting to be told that there really wasn?t any explanation for it, maybe I could take it to another store that fixed Apple's. After 5 hours, one airport card, one ipod, one hardware diagnostic test, and a lot of water I was no closer to finding out why my system was behaving in such an erratic manner."
One reader had his logic board replaced several times, with the problem re-appearing shortly after each repair process:
"I have had this same problem with my Ti PowerBook for more than a year now. The problem started when the machine was only a couple of months old. I've had it in for servicing twice, the first time the entire logic board was replaced. Both times the problem has pretty much disappeared for a month or so before resurfacing again. I agree with your posters comments as to the cause of the problem has that fits my observations to a T. Currently the problem has gotten to the point where the screen on my Ti can go wild at almost any time with the problem popping up 5-20 time a day. Closing the screen part way and opening it again one or two times will cause the problem to go way. Picking the Ti up or any thing else that would flex it will cause the screen to go wild."