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Tunnel Vision On Monochrome Active Matrix Powerbooks
- Thread starter Paralel
- Start date
Wonder if you bake it under a vacuum, kind of like a CRT, what would happen? hmmmm.....
I've had one with the bad tunneling. It was very bad when I first got it, it had been sitting in an unheated garage for quite some time (got it mid winter). I found it cleared up slightly after being in the house for a while. It wasn't completely fixed but it was not nearly as bad as when I first got it.
The other two I had did not have that issue. However, it seems over time one of them did develop tunneling(I sold the screen to Brooklyn).
Would be good to get to the bottom of the issue and figure out if there is a way to reverse it, or at least prevent it on ones that have yet to develop tunneling. Since it seems age is going to take out more and more of those screens.
The other two I had did not have that issue. However, it seems over time one of them did develop tunneling(I sold the screen to Brooklyn).
Would be good to get to the bottom of the issue and figure out if there is a way to reverse it, or at least prevent it on ones that have yet to develop tunneling. Since it seems age is going to take out more and more of those screens.
Well, the screen I ordered has Tunnel Vision.
One thing I noticed on this screen, in the corners where the screen was turning "black", it wasn't losing the ability to display an image, but the polarity of the liquid crystals had inverted. When I moved my pointer into that area of the screen where it had darkened the color of the pointer inverted, but other than that it looked perfectly normal. When I moved the pointer into an area where that was unaffected by the darkening it went back to its typical color.
Does anyone know what could make the liquid crystals in the corners of the monitor invert their polarity like that?
One thing I noticed on this screen, in the corners where the screen was turning "black", it wasn't losing the ability to display an image, but the polarity of the liquid crystals had inverted. When I moved my pointer into that area of the screen where it had darkened the color of the pointer inverted, but other than that it looked perfectly normal. When I moved the pointer into an area where that was unaffected by the darkening it went back to its typical color.
Does anyone know what could make the liquid crystals in the corners of the monitor invert their polarity like that?
Another bit of data for the mystery. I took the panel apart to see if I could find any physical defects. After removing the backlight, diffuser, etc... I was able to see through the panel and it was perfectly clear. I put it back together, put it in my powerbook and it looked great. After about 30 minutes the tunnel vision effect started to appear. I left it on for an hour after that to see how far it would progress. I the took the panel apart again and tried to see what it looked like now and I discovered something. Not only was the darkness at the corners and around the edges present, but the actual menu bar (which was extensively involved after an hour of darkening) was still present! I know it was the menu bar because I could easily read "File", "Special", Finder, etc... when I looked through the LCD. Somehow, whatever this is, can actually cause a complex image to be retained on the screen after power has been cut. So, does anyone know what could case a polarity inversion and allow a image to persist on a TFT-LCD after power is removed but eventually degrade to the point where the LCD looks completely normal, but have it come back again with use?
Because of crystal contamination, or a "charged" state of the Liquid crystal due to an un-wanted DC Bias. The liquid crystal is being driven with a large enough DC-offset most likely caused by leakage currents from either contamination/moisture, or failing TFT transistors in the substrate, this then causes the crystal to build a charge like a capacitor. And thats the effect you see.
dont go too hot, itll melt the polarizing film on the panel. Youll need to heat it just under that softening/melting point and let it simmer for an hour or more.
I decided to go full blast, 2 hours @ 350 F. I removed everything from the screen except for the actual liquid crystal panel itself and the attached control circuitry which cannot be removed. I shielded the control circuitry from the heat using a triple layer of tin foil (operating on the same theory as tin foil masking for a heat gun).
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