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

techknight

Well-known member
It seems to be quite rare to see an unaffected PB170 so it’s good to make sure it’s the same brand because it would be a pretty big discovery if they found a non Hosiden screen.

I wonder if maybe they used better materials possibly on the portables and that’s why they are less affected. Possibly better sealant or better adhesive between layers?

I have a portable LCD that has tunnelvision.

Whats interesting, is i come into some information from an Apple system alert that indicates when these displays were NEW! tunnelvision was somewhat of a problem. Look at this:

1677075877564.png

This tells me the displays always had this problem, its just, its gotten alot shorter as time has gone on. It was known from the beginning!
 

finkmac

NORTHERN TELECOM
Yep, portables are very much susceptible.

Zkhyr2y.png

Note the lower right corner.
 

3lectr1cPPC

Well-known member
I wonder if the portable screens started getting the problem later than other models did. If you dig through the forum archives from 2001-2003 you can already find multiple mentions of the issue on 170s and 180s, but reports of the portable getting it didn’t show up until the 2010s and still seems somewhat uncommon, as opposed to how extraordinarily common it is on PowerBooks. It could be that the Portable’s rarity has something to do with the lack of older data as well though, and there will always be outliers.
 

techknight

Well-known member
Actually that warning is a result of burn-in being possible with those early gen LCD screens.

Tunnel vision does the exact thing before the corners turn dark. I have a portable display that does it. after 15 minutes of it being on, it starts to create an after-image/ghost, and then not much longer after that, the corners start to darken.
 

techknight

Well-known member
I wonder if the portable screens started getting the problem later than other models did. If you dig through the forum archives from 2001-2003 you can already find multiple mentions of the issue on 170s and 180s, but reports of the portable getting it didn’t show up until the 2010s and still seems somewhat uncommon, as opposed to how extraordinarily common it is on PowerBooks. It could be that the Portable’s rarity has something to do with the lack of older data as well though, and there will always be outliers.

Coudl also be how they were stored/treated. The overwhelming number of portables i see, were always stored properly, and in their bags so they are still pearly white, so maybe due to its sheer price at the time, owners took more care. But by the time the 170 etc came out, people basically did whatever.

Could be wrong, but thats just a guess
 

Cedsrepairs

Well-known member
This problem is so bizarre
Air ? moisture ? heat ? Something completely different (electronic weirdness ?)
My PB180 is affected, after around 30min the corner start to get dark
 

Paralel

Well-known member
The leading theory on TV is that it is caused by a failure of the seal that prevents moisture from intruding into the LC layer. Baking the screen, stripped down as much as possible, @ 100 C for 4-5 hours appears to be a long-term fix, removing the moisture and reflowing the seal so it is complete once again. Testing needs to be done to determine if less time can be used, but that is what we know for sure works at this point.
 

Cedsrepairs

Well-known member
I'm currently finishing restoring a nice G4 (which is now my youngest in my collection :) )

Am I over reacting to a factory imperfection, or are the powerbook G4 (aluminium) subject to tunnel vision ?
This is from 2003 !!!
Clearly mine has dark corners at the bottom, and this becomes darker with usage
 

3lectr1cPPC

Well-known member
That’s probably a weak CCFL tube, color displays don’t get tunnel vision. It’s ONLY monochrome and grayscale Active matrix displays.
 

Paralel

Well-known member
I would also be rather surprised as Tunnel vision was never reported in 21st century LCD TFT panels. It is very much a 90's problem.
 

bwinkel67

Member
This problem is so bizarre
Air ? moisture ? heat ? Something completely different (electronic weirdness ?)
My PB180 is affected, after around 30min the corner start to get dark

If you disassemble the panel from the LCD board (it's actually pretty easy) and put it in an oven at 100 celcius for 4 to 5 hours, it should fix it for you. My PB180 would start darkening after a few minutes and after baking it i's now been 8+ months it has not returned.

There are some cool videos out there that I think help to understand what's going on. There is precise spacing between the panels (minute glass beads separating them) and when the edges become disconnected, the electrical charge fed through will build up heat causing warping that introduces darkening around the edges -- according on this video, if he liquid crystal doesn't form the specific helix at a pixel causing what's called the normally white mode, then it ends up blocking some light (i.e. things get darker or all the way black).


You can see this effect in the home made LCD in this video...he used glue at the edges and then filled in with liquid crystal. This is a pretty crude implementation so doesn't have the even spacing and where the glue pulls up he edges, it's dark (ignore the black glue blobs, just look a the surrounding area that doesn't pulse) because the liquid crystals can't orientate:


(Note, you can also see it in the thumbnail...see the slightly dark ring around the glue area in upper left...)
 
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naujoks

Member
My PB 180's display has tunnel vision.
Today I baked the screen for 5 hours at 104C.
It's got a lot better, but it's not completely fixed.
I wonder if giving it another blast would make any difference.
Taking the screen off the PCB had me crazy worried for the hundreds of contacts, which seem to maintain contact simply by being pressed together, but the screen works without any glitches.
 

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bwinkel67

Member
My PB 180's display has tunnel vision.
Today I baked the screen for 5 hours at 104C.
It's got a lot better, but it's not completely fixed.
I wonder if giving it another blast would make any difference.
Taking the screen off the PCB had me crazy worried for the hundreds of contacts, which seem to maintain contact simply by being pressed together, but the screen works without any glitches.

Yeah, it's a bit unnerving to remove the LCD panel and seeing those fine contacts, but it does seem to get put back together. There is a little bit of wiggle room so you don't have to align it 100% (that's the part I worried about since the + symbols did not align for me). The one concern I have of repeatedly opening it was fatigue on the little metal tabs. I have some smaller LCD's (Z88) and they came in two varieties: metal tabs and screws. I would be more comfortable with having screws there. My TRS-80 Pocket Computer 1 also has metal tabs, but its bezel seems to be much thicker/stronger metal.

It's hard to know if a second attempt will fix it or put it at risk. I had someone post on my video that 100 celcius won't damage electronic circuits (he was asking why I took the panel apart). But there is concern that you start adding black spots to the middle of the screen, though I think someone here did that when the temp was higher than 100 celcius. For me, I was going to be unhappy using my BP180 with tunneling so I figured I'd look for something else if it didn't fix it (this was not my 90's Mac but one I purchased for $50 last year on eBay, so I had no connection to it). I had looked at the PB150 since it offered IDE and a passive LCD screen. The lack of ADB port was going to be a fun add-on hack that I found online (soldering four traces on the circuit board since Apple had implemented it but decided no to expose it to users...sigh.

If the fix is indeed about re-flowing the seals, I suppose the seals could be too far gone. After posting the videos above on LCDs, I'm even more of the belief that it's not water related since the liquid crystal itself would end up mixing with moisture -- I don't think it's like oil and water...would love to hear from someone that's played with the substance to get more insight.
 

3lectr1cPPC

Well-known member
There’s an ADB hack for the 150? I could route the port to the empty modem slot in the case! Now if only mine wasn’t falling apart despite my best efforts…
 
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