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New theory on the cause of the infamous Tunnel Vision problem - Testers needed!

3lectr1cPPC

Well-known member
It’s a real shame these LCDs are so unreliable to begin with, they really do look great when working properly. When it comes to fixing them, what other choice do you really have? Either you have an unusable display or you chance ruining it in a different way. The situation with these PowerBooks just stinks all around.
 

Powerbook27364

Well-known member
Yep. No guaranteed way to fix it. Either you get lucky or you don't. Unfortunately I got unlucky but that's just life with these old Macs.
 

Paralel

Well-known member
So its looking like 100C for 5 hours is about it. Also, it is only effective for mild to moderate cases. Higher temps or longer baking seem to result in some kind of damage to the liquid crystal. I guess that means we only have potentially hazardous treatment, although it does appear to be durable. I'm hoping eventually someone will pop up with one of the unicorn screens for the 540 that never tunneled, and getting them to provide the serial number. It might give us an idea of whether earlier or later model screens might be better bets.

One thing I'm interested in hearing from people regarding what model of Powerbook they are using that has TV, how bad the TV is, if it has always had TV since they owned it, or if it didn't, how long did it take to start occurring, and how quickly it appears once the system is turned on. I'm hoping to be able to establish a pattern of some kind.
 

3lectr1cPPC

Well-known member
I’ve got a completely unaffected 170 that doesn’t tunnel whatsoever and never has. I’m not taking apart the display assembly until I have a hinge fix part ready, but when I do I’ll document everything.
 

Powerbook27364

Well-known member
So its looking like 100C for 5 hours is about it. Also, it is only effective for mild to moderate cases. Higher temps or longer baking seem to result in some kind of damage to the liquid crystal. I guess that means we only have potentially hazardous treatment, although it does appear to be durable. I'm hoping eventually someone will pop up with one of the unicorn screens for the 540 that never tunneled, and getting them to provide the serial number. It might give us an idea of whether earlier or later model screens might be better bets.

One thing I'm interested in hearing from people regarding what model of Powerbook they are using that has TV, how bad the TV is, if it has always had TV since they owned it, or if it didn't, how long did it take to start occurring, and how quickly it appears once the system is turned on. I'm hoping to be able to establish a pattern of some kind.
Im thinking I may compile a document of current methods and when they should or shouldn't be used to help people avoid my situation. May allow us to be a bit more organised as well compared to searching all over the place for old threads.
I’ve got a completely unaffected 170 that doesn’t tunnel whatsoever and never has. I’m not taking apart the display assembly until I have a hinge fix part ready, but when I do I’ll document everything.
You should be able to find the 3d printed parts on eBay for a couple bucks. An alternative is 3d printing them yourself if you have a 3d printer. This is what I did and it worked quite well. There are publicly available files on thingiverse for internal standoffs as well as the hinge part.
 

3lectr1cPPC

Well-known member
Im thinking I may compile a document of current methods and when they should or shouldn't be used to help people avoid my situation. May allow us to be a bit more organised as well compared to searching all over the place for old threads.
I started a wiki page on the issue, you can request an account by PMing an admin and they can get it created for you, then add whatever you want to add to it.
You should be able to find the 3d printed parts on eBay for a couple bucks. An alternative is 3d printing them yourself if you have a 3d printer. This is what I did and it worked quite well. There are publicly available files on thingiverse for internal standoffs as well as the hinge part.
I’ve got a place near me that can print high quality ABS super cheap (like $10 for a part). Already got one in my 145, 170 is next.
 

Powerbook27364

Well-known member
I started a wiki page on the issue, you can request an account by PMing an admin and they can get it created for you, then add whatever you want to add to it.

I’ve got a place near me that can print high quality ABS super cheap (like $10 for a part). Already got one in my 145, 170 is next.
Oh awesome, I didn't realise one already existed! That should be helpful for future.

Hopefully you can get your 170 repaired successfully. Mine took quite a bit of fiddling to get it in the right spot but that might have just been my printer not printing the best.
 

Powerbook27364

Well-known member
IMG_0163.JPG
I don't think I posted this before but this was the initial tunnel vision effect for reference if anyone wants to know.
took about 30 minutes to fully tunnel all the way in.
 

Juror22

Well-known member
I think its power related?? not moisture..if i turn on my powerbook 180 on, boot up, shut down and turn on you can almost see the tunnel vision oval starting at more centre of screen and working out..or maybe not the same thing?? Thoughts?
This is really, interesting - particularly in one that hasn't developed any (overt) symptoms of tunnel vision yet. Maybe it is a way to early diagnose, or maybe it is both power and LCD related the it finally starts.
 

Powerbook27364

Well-known member
Well It’s been some time since I last baked my display and since then, almost all of the pixel rot has disappeared. Not sure why but there is only a handful left compared the larger number of original spots.
 

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Paralel

Well-known member
Well It’s been some time since I last baked my display and since then, almost all of the pixel rot has disappeared. Not sure why but there is only a handful left compared the larger number of original spots.

I have heard this before. I think it's that the impacted liquid crystals have have a limited capacity for self-healing.
 

Powerbook27364

Well-known member
I have heard this before. I think it's that the impacted liquid crystals have have a limited capacity for self-healing.
That's interesting. Hopefully the rest will heal themselves. The tunnelling has decreased significantly compared to originally so I would be reasonably happy overall if they healed.
 

stepleton

Well-known member
I have heard this before. I think it's that the impacted liquid crystals have have a limited capacity for self-healing.

This has been my experience as well. I once dropped a crescent wrench on an LCD panel and was worried I'd get chewed out for what looked like a huge windshield chip right in the middle of the display. "Relax," said my labmate, "it'll heal itself." And it did.
 

bwinkel67

Member
That's interesting. Hopefully the rest will heal themselves. The tunnelling has decreased significantly compared to originally so I would be reasonably happy overall if they healed.

Thanks for sharing your experience. I've scanned through the long thread but haven't carefully read everything. When you baked it, how sure were you that you oven kept a constant 212'ish temp and that it was accurate? I put two pizza stones in a gas oven and had an accurately calibrated thermometer to check temp. When I first considered doing it in an electric oven I balked as the temperature swings were way too much, the gas one varied by no more than 3 degrees either way, once the temp settled out.

It may be that if the screen is in really bad shape, it might be difficult (or take more effort) to get it back to normal. I'm still of the mindset that it's not vapor related as the screen behavior doesn't make much sense to me. Perhaps, instead, it's somehow refreshing part of the screen's adhesive so if it's too far gone it may not be able to reseal (or maybe it needs multiple iterations--heat's a funny thing). Just my 2 cents. My screen has been flawless now for over 6 months and I can leave it on for 3 or more hours and nothing changes (I posted a YouTube video of it earlier here, I believe).

I'm sorry that you didn't have the kind of success I (and others) have had but the information you provided is invaluable for future fixes. Keep posting to let us know if it continues to improve and if the tunneling stays somewhat at bay.
 

Paralel

Well-known member
Thanks for sharing your experience. I've scanned through the long thread but haven't carefully read everything. When you baked it, how sure were you that you oven kept a constant 212'ish temp and that it was accurate? I put two pizza stones in a gas oven and had an accurately calibrated thermometer to check temp. When I first considered doing it in an electric oven I balked as the temperature swings were way too much, the gas one varied by no more than 3 degrees either way, once the temp settled out.

It may be that if the screen is in really bad shape, it might be difficult (or take more effort) to get it back to normal. I'm still of the mindset that it's not vapor related as the screen behavior doesn't make much sense to me. Perhaps, instead, it's somehow refreshing part of the screen's adhesive so if it's too far gone it may not be able to reseal (or maybe it needs multiple iterations--heat's a funny thing). Just my 2 cents. My screen has been flawless now for over 6 months and I can leave it on for 3 or more hours and nothing changes (I posted a YouTube video of it earlier here, I believe).

I'm sorry that you didn't have the kind of success I (and others) have had but the information you provided is invaluable for future fixes. Keep posting to let us know if it continues to improve and if the tunneling stays somewhat at bay.

If it wasn't moisture related doing nothing more than storing them with desiccant wouldn't cause an improvement in symptoms. Although not nearly as much as forcing the moisture out.
 

bwinkel67

Member
If it wasn't moisture related doing nothing more than storing them with desiccant wouldn't cause an improvement in symptoms. Although not nearly as much as forcing the moisture out.

I first tried that approach for a year and it had no impact. The LCD behavior doesn't really follow moisture, both pre and post baking. I think moisture success stories are too anecdotal to be useful.
 

Paralel

Well-known member
I'm always open to competing theories. I just can't think of any that explains this process, how heating makes it better, and the ability for the screen to retain an inverted after image in the tunnel vision area when the screen has been disassembled to the point where literally everything has been removed from the screen except the LCD stack (glass, polarizers, etc...), and electronics that must remain attached so as not to destroy the screen.
 

3lectr1cPPC

Well-known member
Here’s my uninformed and perhaps stupid question: would it be possible to verify this by doing some sort of liquid detection test on an affected and unaffected panel to check for any differences?
 

bwinkel67

Member
Or perhaps a humidity test would help. Bake a screen to fix it, then put it next to a humidifier and see if it comes back. That would be additional observational data. Then if it comes back you can simply re-bake it to get rid of it. For those that think it's humidity, it should be an easy and safe test.

The reason I'm skeptical of moisture is that if there are gaps in the screen that cause moisture to enter, then why would baking it keep it away for over 6 months, especially when part of those 6 months are July, August, and September; very humid months. Wouldn't it just enter again when the pressure changes during some minute expansion of the panels, while sucking in air? Also, having seen the way vapor behaves between window panes, it doesn't disappear as orderly and timely as the LCD panel has done for me when shutting down and having it completely go away in a somewhat set period of time. I would think it might persist for much longer (days) around the edges depending on humidity conditions outside...i.e. during really humid times, wouldn't the tunneling just stay as is?

I'm not discounting it as a theory completely, but I feel like that's been the main fallback and thrown out there as fact. Heating and cooling between two close surfaces and their potential movement away from each other when not fastened together due to lack of sealant seems just as plausible and potentially could be more constant. As the screen warms up due to electricity flowing through it, the panels start minutely separating and that could be causing the constancy of the tunneling pattern. Just as heating could be vaporizing moisture between panels, so could it be re-flowing sealant, causing less movement between those panels. The latter would not be impacted by by outside condition. Why does vacuum sealing also work? Again, could be sucking out the moisture, or it could be pushing the panels together, thus creating a tighter bond (note, I've only heard anecdotal stories about someone trying that technique). Why does storing it in rice (or some other dehydration method) for 10 years work (that's one that I heard)? Well, again, that's a hard one, to say something worked because it was stored for 10 years. I mean, how was it stored? How bad was it before hand? Was it completely cured?
 

Powerbook27364

Well-known member
Thanks for sharing your experience. I've scanned through the long thread but haven't carefully read everything. When you baked it, how sure were you that you oven kept a constant 212'ish temp and that it was accurate? I put two pizza stones in a gas oven and had an accurately calibrated thermometer to check temp. When I first considered doing it in an electric oven I balked as the temperature swings were way too much, the gas one varied by no more than 3 degrees either way, once the temp settled out.

It may be that if the screen is in really bad shape, it might be difficult (or take more effort) to get it back to normal. I'm still of the mindset that it's not vapor related as the screen behavior doesn't make much sense to me. Perhaps, instead, it's somehow refreshing part of the screen's adhesive so if it's too far gone it may not be able to reseal (or maybe it needs multiple iterations--heat's a funny thing). Just my 2 cents. My screen has been flawless now for over 6 months and I can leave it on for 3 or more hours and nothing changes (I posted a YouTube video of it earlier here, I believe).

I'm sorry that you didn't have the kind of success I (and others) have had but the information you provided is invaluable for future fixes. Keep posting to let us know if it continues to improve and if the tunneling stays somewhat at bay.
I did test it with a thermometer and it did vary by about 10-15 degrees F. So that wasn’t ideal and may have caused the problems. I don’t have a gas oven unfortunately.

I’m with you on the possibility that it is resealing the panel. If it truly was moisture after the amount of time I had baked it it would have disappeared completely. But even then it’s weird. Maybe it’s just too worn out to fix at this point.

Side note, my panel is clear from pixel rot now so that’s pretty nice. I’m hesitant to try baking it again since the pixels were damaged last time.
 
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