13 Replies Latest reply: Feb 18, 2013 1:18 PM by peterlrowley
martin101 Level 1 (0 points)

I have a Powerbook G4 1.67 Ghz that has been having intermittent display problems. The powerbook is running OS 10.5.


The display produces a banding effect that comes and goes - more often than not the monitor is banding.


When the computer is powering up the gray Apple loading screen with the spinning wheel displays fine.  The blue screen right before the desktop appears displays fine.  Once the desktop apears the banding effect begins.  Sometimes it comes and goes.


You can still use the mouse if you can locate the part of the screen you would like to click on.  If I hook up an external monitor to the powerbook - the external display displays fine.


If I startup from the OS Disks - they display works fine.  When I run the hardware test from the CD - it works and displays fine. Hardware test doesn't report problems.


I've linked two photos of the screen. The first photo shows the screen when it not operating properly.  The second photo shows the same screen when working okay.


Bad Screen



Good Screen



Does anybody have any expeience troubleshooting this issue? Any help is appreciated.

  • old comm guy Level 4 (2,240 points)

    Does the problem show up with a Safe Boot (holding down shift key at start)?


    Just from looking at your picture, it seems consistent with a cable problem between the logic board and the display unit, but the fact that it only shows up when the system is booted is suggestive of something more sinister, which I why I asked about safe boot.


    Does the problem respond to a light rap on the top of the computer near the display hinge?  I am not sure where the cable exits be main box and goes to the display on your machine, so I can't be more specific, though it seems that the display cable comes off the logic board under about the F10 key or so.  The other end of the cable is near the top center of the display, so that would be another area to "thunk" the back of the display to see if that clears up or affects the breakup.

  • Allan Jones Level 7 (33,690 points)

    Martin101 wrote:


    "If I hook up an external monitor to the powerbook - the external display displays fine."


    That's a pretty strong indication of a cable problem. In addition to old comm guy's sage advice, you can watch the image while changing the angle of the display. That usually shows up any potential cable faults and points to the fault being in or near the hinge.


    The head-scratcher for me is why this doesn't happen when you boot from a system disk. Can you use the external monitor to change the desktop resolution of the internal display. If you are in extended desktop mode, you should be able to see settings for both monitors from the external. F7 toggles between mirrored video and extended desktop, as i recall. Does toggling make a difference?

  • martin101 Level 1 (0 points)

    I started the machine in safe mode and the the banding showed up briefly and never showed up again. Maybe, 15 seconds.


    I started the machine in standard mode and the computer worked fine for a while and the banding showed up. 


    One thing I can mention is that when the banding shows up - if I change the background to a solid white color - either in the browser (a new tab) or in the finder (change background to solid gray in system prefs) the flicker banding and ghosting stabilizes - doesn't go away but it isn't as drastic.


    When the banding showed up in normal mode - I restarted to safe mode and the banding went away.


    I restared in standard mode and the flicker hasn't showed up.


    I rapped around the case and hinges and back of display and didn't get a response either way.


    I've had the unit plugged in all morning - battery is also recharging - and the flicker hasn't showed up a whole lot.


    Granted, the last time I powered up it was the reverse - the flicker was the entire time with biref pauses of operationability.  This time, I was running off of battery power, but I've noticed it happens running off of the battery and off of the AC Power.

  • martin101 Level 1 (0 points)

    I tried the monitor at different angles and rapped around the hinges and no response on the display either way.


    When the banding occurs, you can still navigate around the desktop when it isn't too bad - but the top of the monitor may display on the bottom of the screen - and chost itself around the middle of the screen.


    I can manuever my pointer around to the system preferences and changed the monitor resolutions and color preferences and it didn't have any effect on the banding.


    If I do a mirrored dektop, the external monitor is fine but the powerbook monitor will have fits of bandiing.


    I can take this powerbook apart like it was an old volkswagen.  I just replaced the hard disk - although this was occuring before the hard disk went out .  I will open it up and check the monitor connections and report back.


    It's been working fine for the better part of 3 hours but sooner or later the banding will begin and no matter how many restarts, system prefs tweaks, etc. it may continue until it wants to stop  Sometimes it won't stop but when I goto startup the next day, it will work fine like todayl.

  • Texas Mac Man Level 8 (46,560 points)

    Some of the display settings are stored in NVRAM.


    Try a PRAM/NVRAM reset. http://support.apple.com/kb/ht1379


    Another way to reset NVRAM.


    Restart your mac & immediately depress the Command+Option+O+F keys which will display the Open Firmware screen. Then type the following:

    reset-nvram Then press the Return key & type:

    set-defaults  Then press the Return key & type:

    reset-all Then press the Return key & your Mac will reboot.


     Cheers, Tom



  • martin101 Level 1 (0 points)

    Thanks TMM.  Per your post, I did reset the PRAM and the NVRAM.  I haven't checked the monitor connections yet but the banding has appeared very little since my original post yesterday.  Resetting the RAM's is the only cause-effect action that I've taken on the machine so I'd like to see how is performs after this action.


    I'd like to definitively troubleshoot the cause of the problem.   I do have to reset my date and time whenever my battery goes out completely.


    I will revisit this post when the problem reappears.  Once it does, I will reset the RAM's once again.  After that, I will check the monitor connections inside he machine.


    Still looking forward to any input others may have. Thanks all.

  • old comm guy Level 4 (2,240 points)

    martin101 wrote:


    I'd like to definitively troubleshoot the cause of the problem.   I do have to reset my date and time whenever my battery goes out completely.


    Hmmm.  Sounds familiar.



  • martin101 Level 1 (0 points)

    Thanks OCG.  I haven't had any issues with my computer since resetting the PRAM and the MVRAM.


    After reading the link in your post above it got me thinking.  I haven't had any issues since yesterday's reset and I also have not operated the computer without the power or allowed the battery to drain completely.


    I am going to operate the computer without AC power and let the battery to expire completely and see if the banding issues appear again.  I will report the results.


    Thanks all.

  • martin101 Level 1 (0 points)

    I closed my Powerbook having the display issues and put it to sleep overnight - without the AC connected.  This evening when I opened the Powerbook to use it (84% battery charge remaining), the banding issues have appeared once again.


    I restarted the machine and it was still displaying the banding issues on the monitor.


    After restarting the computer and resetting the PRAM and NVRAM as above, the banding issue seems to be gone for now.


    It seems that this reset makes the Powerbook display work with no bugs.   I researched and found this article related to performance and PRAM / LogicBoard Battery:




    After the feeedback in this thread and troubleshooting the troubled Powerbook - I am begining to think my display issues may be LogicBoard Battery / PRAM related. Especailly since the PRAM - NVRAM reset had in immediate positive effect on the performance of the display.

  • martin101 Level 1 (0 points)

    I'm back to discuss the same issue of my original post. I'm still having the same issue banding and garbled display issues. The issue continues to appear and reappear. Sometimes it shows up for hours and sometimes it doesn't show up for hours.


    I've isolated the issue and noticed a solution and am seeking an explanation why the computer is behaving in this manner.


    If the banding appears on the display I can correct the problem by applying pressure with my palm to the lower right corner of the upper casing in the middle of the area that is below the keyboard/sound vents and the trackpad.


    If I press down correctly, something is adjusted and the banding disappears and the monitor performs as normal.  Keep in mind that this does not effect the external/mirrored monitor that I have connected at the same time.  The external monitor has never been effected by the problem of the banding and garbled screen that is mentioned in my original post.


    I think this problem has been correctly isolated and I'm looking for the solution. I'm looking forward to any feedback regarding this issue so I can correctly perform the repair.

  • istella Level 1 (0 points)

    I have a 1.67 17" with similar but less severe problems.   Almost all of the time, the display - in this case a hi-res A1139 display - has no problems at all; it works fine for hours.  I can, however, make it flicker by opening and almost closing  the display back and forth, in which case I see the display flicker with horizontal lines and criss-cross images.  I've tried all the stuff suggested in this thread, i.e. tapping the back and knocking on the hinges, which does not produce any flicker. Pressing on the keyboard cannot have any effect, since you cannot press hard enough to touch the display cable without bending the upper case.  If my assumptions are correct, i.e. the display is controlled only by the inverter cable and the display cable, then the problem must be with with either of those cables.  In my case, I suspect one of the two cables is getting pinched somewhere around the hinges.  If that is the case, and the suspect cable has been frayed, it is not an easy fix, requiring the display to be taken apart and replacing either of the 2 cables. I will report back if I make any progress. 

  • roddyrod Level 1 (0 points)

    Thanks for the post.  I guess I was lucky until just recently, where I started having a 1 inch white vertical band facing right side, with my faithful G4 1.67 GHz PB.  I am at the beginning of my search for solutions to this problem.  I am "assuming" that someones solution will help.  Please let us know how it goes.  My PB is well out of warrenty.

  • peterlrowley Level 1 (0 points)

    I have a Powerbook G4 with exactly this problem, pretty badly.  Fortunately, I don't have to use it much anymore, but occasionally I do.  The odd thing is that the PRAM reset works for me just fine, but only for about 5 minutes.


    I do have another temporary solution to add to the mix.  Spreading out the fingers of both hands and then applying them in one motion to press (well, sort of slap) on the keyboard as a whole has fixed this immediately at least three times today.  And it seems to be holding... it's been good for over an hour.