Sideburn
Well-known member
Hey all,
So I have taken the risky plunge into making an attempt at repairing my non-backlit LCD panel on this Macintosh Portable I have been repairing and restoring.
The display has the classic "dead pixel" horizontal lines... At first it only had one.. Then yesterday another one has appeared through the vertical center:
My first thoughts were that there's a problem with the conductive rubber zebra strips or the contacts on the glass/pcb need cleaning so I separated the glass/strips from the PCB and cleaned the PCB contacts... I didn't risk trying to peel the rubber zebra strips off the glass without having another set and this was when I realized that these particular strips have TWO black strips of carbon that are about 4mm apart from each other...
Is there even a source to getting zebra strips like this?!?
Has anyone actually replaced the zebra strips on these LCDs and done a repair?
Heres a photo showing what I am talking about:
Continuing on, I successfully re-attached the lcd to the PCB and didn't do any further damage but didn't do any help either.
Next I ruled out the cable by doing a conductivity test with my DMM. All good.. Not the cable.
I started to suspect it may be one of the driver chips since these lines/pixels aren't really "dead". It's more like they are inverted. Instead of black, they are white and vice versa (when I power down, these lines turn black).
I started to run my wet finger across the pins on the T7900 driver chips and found when I ran it across a particular chip, it was drawing faint horizontal lines in the same problem area on the display.
I inspected this chip and it looked like there was some slight corrosion on the pins so I cleaned and re-flowed them but no luck...
I then lifted the capacitor (C11) off of the back of the PCB on the display and discovered that the display now went crazy filling all of the pixels black:
If I watched closely I could sill see the problem horizontal lines though so they were still flickering in and out, and when I took a video, the camera demonstrated this...
But still, with the aid of persistence of vision, it sure looks like these pixels are turning on and off to me, ruling out a connectivity problem, no?
I also noticed that when the capacitor is removed and I power down, the screen goes full blank much faster than with the cap installed.
So this seems like it is also a clue..
Here is a clip of me powering it down WITH the capacitor in place and you can see how the problem lines turn black and fade out: http://www.sideburn.com/vid/cap.mov
And here is a clip of me powering it down WITHOUT the capacitor in place and you can see how the lines disappear immediately: http://www.sideburn.com/vid/no-cap.mov
So what do you guys think? Does this prove that the issue is one of the driver chips and do you think it is the T7900 that I ran my finger across that was painting lines in the same area and had what looks to be some corrosion?
And if so, where in the heck might I be able to find a replacement T7900? so far a google search has resulted in no luck finding one.
I have cleaned, re-capped, replaced the hybrid board, and repaired the logic board and Ive replaced the hard drive, 3d printed and rebuilt a perfect replica of the original battery. This machine is almost perfect except the the damn LCD display and I cannot find a replacement anywhere so I really want to fix it and be undefeated!
Thanks for any info,
-Tavis
So I have taken the risky plunge into making an attempt at repairing my non-backlit LCD panel on this Macintosh Portable I have been repairing and restoring.
The display has the classic "dead pixel" horizontal lines... At first it only had one.. Then yesterday another one has appeared through the vertical center:
My first thoughts were that there's a problem with the conductive rubber zebra strips or the contacts on the glass/pcb need cleaning so I separated the glass/strips from the PCB and cleaned the PCB contacts... I didn't risk trying to peel the rubber zebra strips off the glass without having another set and this was when I realized that these particular strips have TWO black strips of carbon that are about 4mm apart from each other...
Is there even a source to getting zebra strips like this?!?
Has anyone actually replaced the zebra strips on these LCDs and done a repair?
Heres a photo showing what I am talking about:
Continuing on, I successfully re-attached the lcd to the PCB and didn't do any further damage but didn't do any help either.
Next I ruled out the cable by doing a conductivity test with my DMM. All good.. Not the cable.
I started to suspect it may be one of the driver chips since these lines/pixels aren't really "dead". It's more like they are inverted. Instead of black, they are white and vice versa (when I power down, these lines turn black).
I started to run my wet finger across the pins on the T7900 driver chips and found when I ran it across a particular chip, it was drawing faint horizontal lines in the same problem area on the display.
I inspected this chip and it looked like there was some slight corrosion on the pins so I cleaned and re-flowed them but no luck...
I then lifted the capacitor (C11) off of the back of the PCB on the display and discovered that the display now went crazy filling all of the pixels black:
If I watched closely I could sill see the problem horizontal lines though so they were still flickering in and out, and when I took a video, the camera demonstrated this...
But still, with the aid of persistence of vision, it sure looks like these pixels are turning on and off to me, ruling out a connectivity problem, no?
I also noticed that when the capacitor is removed and I power down, the screen goes full blank much faster than with the cap installed.
So this seems like it is also a clue..
Here is a clip of me powering it down WITH the capacitor in place and you can see how the problem lines turn black and fade out: http://www.sideburn.com/vid/cap.mov
And here is a clip of me powering it down WITHOUT the capacitor in place and you can see how the lines disappear immediately: http://www.sideburn.com/vid/no-cap.mov
So what do you guys think? Does this prove that the issue is one of the driver chips and do you think it is the T7900 that I ran my finger across that was painting lines in the same area and had what looks to be some corrosion?
And if so, where in the heck might I be able to find a replacement T7900? so far a google search has resulted in no luck finding one.
I have cleaned, re-capped, replaced the hybrid board, and repaired the logic board and Ive replaced the hard drive, 3d printed and rebuilt a perfect replica of the original battery. This machine is almost perfect except the the damn LCD display and I cannot find a replacement anywhere so I really want to fix it and be undefeated!
Thanks for any info,
-Tavis
Last edited:
