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Tunnel Vision On Monochrome Active Matrix Powerbooks

Spode

Active member
Hi All!

I just managed to get hold of an immaculate PB170 and after a couple of hours of use I get a small amount of screen burn and then the bottom left corner a bit of creeping black. This obviously led me to this thread. Mine is not severe enough that I feel it's worth doing anything at this point.

However, I started wondering - what causes this to happen more as the screen is in use. Could the heat from the CCFLs be causing the moisture to migrate? In which case, could upgrading the screen to use LED back lights perhaps lengthen the amount of time it takes for it to happen - or mitigate it entirely in situations like mine where it takes a couple of hours. Thoughts?
 

AndyO

Well-known member
Hi All!

I just managed to get hold of an immaculate PB170 and after a couple of hours of use I get a small amount of screen burn and then the bottom left corner a bit of creeping black. This obviously led me to this thread. Mine is not severe enough that I feel it's worth doing anything at this point.

However, I started wondering - what causes this to happen more as the screen is in use. Could the heat from the CCFLs be causing the moisture to migrate? In which case, could upgrading the screen to use LED back lights perhaps lengthen the amount of time it takes for it to happen - or mitigate it entirely in situations like mine where it takes a couple of hours. Thoughts?

Pretty much the same experience with my 180. It takes about 2 hours before the corners begin to darken. Generally, at that point I put it to sleep or power down since I am usually done with it by then anyway.

One thing that strikes me however is that the tunneling continues to worsen even after the system is powered down - it can be seen quite clearly even against the dark background. Wouldn't that preclude a direct heat-related cause, since whatever heat is generated by the backlight would dissipate pretty quickly?
 

Spode

Active member
Pretty much the same experience with my 180. It takes about 2 hours before the corners begin to darken. Generally, at that point I put it to sleep or power down since I am usually done with it by then anyway.

One thing that strikes me however is that the tunneling continues to worsen even after the system is powered down - it can be seen quite clearly even against the dark background. Wouldn't that preclude a direct heat-related cause, since whatever heat is generated by the backlight would dissipate pretty quickly?
Not necessarily. If the heat causes the moisture to migrate - it might take longer than simply "cooling down" for the moisture to migrate back. I guess ultimately the question would be, if it IS moisture - what is it about operating that causes the problem and heat seems an obvious culprit!

I'm very lucky that even the battery works on this thing - so I did a couple of hours the other day on battery and it was just starting to creep in. Then I stopped for no more than an hour and then came back to it and it had already reset back to normal. I've not timed how quickly it happens (that might give a clue?).

Thinking about it -one way to test the theory is to wait for it to show, and then turn the brightness all the way down until the backlight turns off. I would have thought if you then left it, if my theory is correct - it will return to normal without the screen being turned off completely.
 

AndyO

Well-known member
Not necessarily. If the heat causes the moisture to migrate - it might take longer than simply "cooling down" for the moisture to migrate back. I guess ultimately the question would be, if it IS moisture - what is it about operating that causes the problem and heat seems an obvious culprit!

I'm very lucky that even the battery works on this thing - so I did a couple of hours the other day on battery and it was just starting to creep in. Then I stopped for no more than an hour and then came back to it and it had already reset back to normal. I've not timed how quickly it happens (that might give a clue?).

Thinking about it -one way to test the theory is to wait for it to show, and then turn the brightness all the way down until the backlight turns off. I would have thought if you then left it, if my theory is correct - it will return to normal without the screen being turned off completely.
I see your point - I was thinking of it in terms that if moisture is the root cause, and heat is the catalyst that causes the issue to appear, then it is still the moisture at issue that has to be resolved, because whatever heat is present during use will be present when the laptop is in use anyway.

I know that on my 180, when I can see the impact of tunnel vision after a couple of hours or so and I put the laptop to sleep or power it down, the problem continues to worsen for some time before slowly (It appears) fading again. I'll try turning the backlight off next time and see what happens.
 

AndyO

Well-known member
Well, almost 3 hours of use and the tunnel vision issue was becoming quite noticeable, so I left the 180 on, but turned off the backlight. The tunnel vision issue got steadily worse, to the point that after an hour when it would normally be visibly receding after power-down, it was still getting worse with the backlight off but the system running. After two hours, it was worse than I have seen it before.

90 minutes after shutting the powerbook down, the issue is still clearly visible - it would normally not be after that time.
 

Spode

Active member
Well, almost 3 hours of use and the tunnel vision issue was becoming quite noticeable, so I left the 180 on, but turned off the backlight. The tunnel vision issue got steadily worse, to the point that after an hour when it would normally be visibly receding after power-down, it was still getting worse with the backlight off but the system running. After two hours, it was worse than I have seen it before.

90 minutes after shutting the powerbook down, the issue is still clearly visible - it would normally not be after that time.
I guess that puts to death the idea of it being heat from the backlights!
 

AndyO

Well-known member
I guess that puts to death the idea of it being heat from the backlights!

It didn't seem heat related, or at least not directly, since heating display panels in an oven as discussed previously in the thread appears to help mitigate the issue, but I don't really have an alternative suggestion - and even after being powered down for another 90 minutes or so, the 180 screen still shows signs of tunneling, still receeding, long after it normally would have gone.

I can buy into it being caused by moisture, and that different storage and/or usage conditions impact on how bad and how swiftly it appears when in use, but what then makes the issue become visible, and why does it take time to recede after use?

My 180 is sufficiently slow to develop the problem that I can still use it quite happily, but it does rather put me off any other active matrix screen - at least in the 100-series. Yet, I think I have read that color displays aren't affected... they're just a bit small in this range of laptops.
 

Spode

Active member
It didn't seem heat related, or at least not directly, since heating display panels in an oven as discussed previously in the thread appears to help mitigate the issue, but I don't really have an alternative suggestion - and even after being powered down for another 90 minutes or so, the 180 screen still shows signs of tunneling, still receeding, long after it normally would have gone.

I can buy into it being caused by moisture, and that different storage and/or usage conditions impact on how bad and how swiftly it appears when in use, but what then makes the issue become visible, and why does it take time to recede after use?

My 180 is sufficiently slow to develop the problem that I can still use it quite happily, but it does rather put me off any other active matrix screen - at least in the 100-series. Yet, I think I have read that color displays aren't affected... they're just a bit small in this range of laptops.

Mine is definitely usable enough, but I was drawn to the 170 because I remember how much I loved the screen, so it would be a real shame to be sitting on a ticking timebomb. The people with half-broken or screens in much more severe shape are in the best position to try and experiment/solve this.

I'm not sure if you watch Adrian's Digital Basement, but he did a video on how baking chips in the oven (might) fix/change behaviour on chips and referenced an article suggesting it was due to electro-migration in the semiconductors, but I can't find the article to reference. It's mostly unsubstantiated, but it could be a possible explanation if it's not moisture related.

One thing I find odd is everyone suggesting, it always starts out the outside and works its way in. This is not the case for me - yes, it is noticeable in the corners worst, but if, for example, I left the same thing on screen - I would see "burn" left behind of the old image and that's right in the centre of the screen.
 

AndyO

Well-known member
The tunnel vision problem doesn't seem consistent across systems - for example, I've read descriptions where in the darkened areas, the screen is actually inverted, others, that there's apparent screen burn such as you describe, but neither seems to be the case on my 180.

On mine, the screen darkens primarily on the left-hand side, with the top corner being worst, and there's nothing visible in the darkened areas at all.

Perhaps there are slightly different causes or circumstances that define the outcome, or perhaps it's differences in the panels between black and white and greyscale ones. I don't really have a clue!

My 180 is also usable as it is for the purposes I need, so other than a bit of 'range anxiety' in terms of trying to get work done fast enough that the tunneling doesn't get time to happen, I'm reluctant to experiment just in case I make it worse. I have begun using my 520c instead sometimes, but the 180 screen is so much better - and I don't need color.

If it is moisture related in cause, then the fact mine is stored and used in a low-humidity environment will hopefully help avoid the tunneling getting too much worse, but the experiment the other day with leaving it running and just turning the backlight off does show it could get a lot worse in regular use than it currently does!
 

Livingroom

Well-known member
The tunnel vision problem doesn't seem consistent across systems - for example, I've read descriptions where in the darkened areas, the screen is actually inverted, others, that there's apparent screen burn such as you describe, but neither seems to be the case on my 180.

On mine, the screen darkens primarily on the left-hand side, with the top corner being worst, and there's nothing visible in the darkened areas at all.

Perhaps there are slightly different causes or circumstances that define the outcome, or perhaps it's differences in the panels between black and white and greyscale ones. I don't really have a clue!

My 180 is also usable as it is for the purposes I need, so other than a bit of 'range anxiety' in terms of trying to get work done fast enough that the tunneling doesn't get time to happen, I'm reluctant to experiment just in case I make it worse. I have begun using my 520c instead sometimes, but the 180 screen is so much better - and I don't need color.

If it is moisture related in cause, then the fact mine is stored and used in a low-humidity environment will hopefully help avoid the tunneling getting too much worse, but the experiment the other day with leaving it running and just turning the backlight off does show it could get a lot worse in regular use than it currently does!
My PB180 inverts perfectly. I can still see everything after a few hours but inverted. Resets in about 3 hrs
 

glay78

Well-known member
Check out this video, seems like baking the LCD panel only with 85deg Celsius for 9 hours did help.

 

Johanncerecke

New member
Hi everyone, my name is Johann and I made the video above. Happy to answer any questions anyone has about my process. Hope people will find it helpful!
 

glay78

Well-known member
Hi everyone, my name is Johann and I made the video above. Happy to answer any questions anyone has about my process. Hope people will find it helpful!
Great! Nice to “see” you here. Indeed that’s gonna give some hope and help to many of us here.
 

LCARS

Well-known member
Hi Johann. Thanks for the post and video. Good catch on the tiny orientation windows. Also, nice B&O Pentas! I use my MKII pair daily.
 

k24a1

Well-known member
Does the 145B suffer from this? I have one sitting around that needs a hinge mount but also might need a screen recap.
 

AndyO

Well-known member
Does the 145B suffer from this? I have one sitting around that needs a hinge mount but also might need a screen recap.
The 145B is passive matrix so it doesn't have this issue... of course being passive matrix it has other issues typically instead! Recapping the screen would help the common passive matrix ghosting and shading issues.
 
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