Tunnel vision on PB170

[bwinkel67]

Here is a video of my PowerBook 180 about 6 months after having been baked at 100 degree celcius for 5 hours. I can leave it on for hours and no tunneling. It has not been specially stored/sealed in a dry place.

You do see a bit of flicker on the left on all-black background...I'm wondering if that's the back-light.

Note that closeup of LCD screen starts at the 3:30 mark.

 

[3lectr1c]

Very nice! Didn't know you had a YouTube channel either! I'm going to actually try to record an hour-long time lapse of my 540's display and upload it to my second channel. Just don't know if my AC Adapter will keep it running that whole time... My blackbird charger has been flaking out lately.

 

[Paralel]

Here is a video of my PowerBook 180 about 6 months after having been baked at 100 degree celcius for 5 hours. I can leave it on for hours and no tunneling. It has not been specially stored/sealed in a dry place.

You do see a bit of flicker on the left on all-black background...I'm wondering if that's the back-light.

Note that closeup of LCD screen starts at the 3:30 mark.

I would say this essentially seals it. Now we just have to experiment with less time. The less time we can stress the screens, the better. But 5 hours may be the magic number. We'll have to get people to experiment to determine the time going forward. I give major credit to @bwinkel67 for making this substantial breakthrough. The correct temperature is 1/2 the battle won.

As far as time, I think starting out with rough increments is the best way to go, 4 hours, 3 hours, 2 hours. Once we reach the inferiority point, we can take it to 30 minute increments. I don't see a point in going finer than that. I doubt 15 minutes one way or another will make any difference.

I've got one 540 on the way to try this with. I'm going to see if I can nab any others.

 

[3lectr1c]

@Paralel, you’ve seen a bunch of these 540s. Any idea what’s causing the yellow splotches at the bottom of the display?

 

[Paralel]

Sigh. The curse of "poor packaging" (and/or possibly "rough handling", given the time of year when the shipping occurred) has claimed the life of the 540 that I was expecting. As such, I will have to wait until I can get my hands on another one to contribute to the baking effort. The one interesting thing I was able to glean from it is that this particular panel is slightly different compared to all the others I have seen. All the 540 screens I've encountered have all been marked "HY41..." this one is marked "HY40..." so I'm guessing it's an earlier run of the screen.

As far as the baking is concerned, it is possible to disassemble the screen all the way down to just the glass, polarizers, and attached electronics, without harming the screen itself. As you can see here:



Any debris that gets on the screen before it can be reassembled can usually be removed with just a puff of canned air. As far as protecting the electronics attached to the screen, I've used tin foil. Anything that can "reflect" IR will work. The best would be some of that IR filtering glass/polymer, but I am sure that wouldn't be cheap to acquire.

@Paralel, you’ve seen a bunch of these 540s. Any idea what’s causing the yellow splotches at the bottom of the display?

If I'm not mistaken, that looks like some condensation type water damage I've seen with LCD screen that have been stored in places where there is condensing humidity. I find it's rather common for some temperature/humidity unregulated storage spaces. The splochiness, variable intensity, and the fact it is at the corners of the screen, which is where water ingress is most common, would make it a very likely candidate.

 

[3lectr1c]

Rats. Any way to fix it or am I looking at a screen replacement? Funny thing is that I’d expect the tunnel vision to be way worse if it’s been exposed to that much water. I’d also expect the batteries to have leaked worse in that case but they were fine and even still held some weak charge (not enough to power the laptop though). Perhaps whatever caused this happened a very long time ago.

 

[Paralel]

Rats. Any way to fix it or am I looking at a screen replacement? Funny thing is that I’d expect the tunnel vision to be way worse if it’s been exposed to that much water. I’d also expect the batteries to have leaked worse in that case but they were fine and even still held some weak charge (not enough to power the laptop though). Perhaps whatever caused this happened a very long time ago.

It likely did happen a long time ago, looking at the video, it appears to have completely dried, which takes a long time given how long diffusion of moisture occurs at ambient conditions. Unfortunately, as far as I am aware, it is unfixable. However, I am no expert on water damaged screens. It might be possible to rescue it. Hopefully someone here knows more.

 

[3lectr1c]

Well, it works for now, but yeah, will probably search for a parts unit at some point in the future when the time is right.

 

[Paralel]

It's too bad the 540 screen has such a serious flaw. It is the best grayscale LCD ever used in a 68k system as its 6-bit (64 grays). Everything else has either 1 or 4-bit grayscale screens. The colors screens are also not capable of as many grays. The color screens that are capable of displaying thousands of colors are only capable of 32 grays. In reality, I actually tested the 540c Toshiba screen in grayscale mode using a 256 grayscale image and only 27 grays were actually discernable under the absolute best circumstances. I'd really be interested in seeing how many grays one can get on the 550c screen. It should be 32 or less, but who knows.

 

[3lectr1c]

One thing worth noting is that I believe that my 540 is improving on its own. My 1 hour time lapse shows the issue apparent around 40 minutes in, but although I never timed it, it felt more like 20 a few months ago when I first got it.

 

[Paralel]

One thing worth noting is that I believe that my 540 is improving on its own. My 1 hour time lapse shows the issue apparent around 40 minutes in, but although I never timed it, it felt more like 20 a few months ago when I first got it.

That is interesting. I've never heard of it improving on its own without intervention. Do you happen to live in a very dry climate? I'm thinking that where it came from was a much more wet climate, and where you are is much drier, leading to it naturally "drying".

 

[3lectr1c]

The most specific I’ll get is “close enough to make it to VCF East”, not really wet or dry climate really. It shipped from Oregon. It’s kept in my basement setup, which has a dehumidifier running at all times. Not positive it’s actually getting better because I could have estimated the time back then wrong, but we’ll see what happens over the next few months. It’s also stored open on a shelf at the moment as I haven’t installed new hinge mounts yet.

 

[Paralel]

The most specific I’ll get is “close enough to make it to VCF East”, not really wet or dry climate really. It shipped from Oregon. It’s kept in my basement setup, which has a dehumidifier running at all times. Not positive it’s actually getting better because I could have estimated the time back then wrong, but we’ll see what happens over the next few months. It’s also stored open on a shelf at the moment as I haven’t installed new hinge mounts yet.

Ok, so if it was near the coast or a lake, its new home, especially with a dehumidifier, is likely to be drier. We know that it is possible to reverse the process to a limited extent using a simple humidity differential (under vacuum + slica) and the fact that a simple humidity gradient is enough to reverse it is the strongest evidence we have to date that it is a moisture based injury. So, it makes sense. The screen is likely to improve until the it reaches the point where there isn't enough of a gradient to drive the humidity out.

It's too bad more manufacturing information isn't available from that time period so we can understand what went wrong with MTFT active matrix screens back in the 90's that caused this phenomenon across multiple years/models. Whatever sealant they used specifically for MTFT eventually underwent some kind of process that lead to a seal failure. I wish we had someone in the Mac community that was capable of a materials analysis and could tell us exactly what happened, was it deterioration (such as a polymer failure)? etc...

 

[3lectr1c]

Also worth noting is that I got it in august, and now I’m testing in December, so temperature could be a factor as well. My basement can get kind of chilly in the winter. I’ve got to repeat the test inside the fridge at some point, although I’ve got to recap my PSU first, it’s starting to flake out on me if I use it for too long.

 

[Paralel]

Also worth noting is that I got it in august, and now I’m testing in December, so temperature could be a factor as well. My basement can get kind of chilly in the winter. I’ve got to repeat the test inside the fridge at some point, although I’ve got to recap my PSU first, it’s starting to flake out on me if I use it for too long.

I look forward to your lower temp test. Since temperature dictates molecular activity, I would imagine its possible that it could slow down the interaction between the water and the screen matrix. If so, it might slow time to onset. My PSU is starting to do the same thing. I really didn't want to have to recap it, but I don't see any other option at this point. Still better than the other 4 that all just put out magic smoke when plugged in.

 

[3lectr1c]

They’re all gonna need it at some point… I’ve got 2. The one that dies after running for a while was the first one I had (got it with my 540c) and then the other one I got with my 540. It ran for a grand total of 20 whole minutes when I first got it then promptly died and let out the strong odor of cap juice… I’ve already busted it open with a vice, just gotta order the caps then it should be good to go again. Should be a good new years project. Adapter #1 doesn’t smell of cap juice but they’re clearly weak either way. Also have a dead 100 series and a 5300 series adapter I need to recap. Both have been busted open already, just gotta get them changed. 100 series supply is real nasty, those ELNA caps are no joke.

 

[Paralel]

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.

 

[3lectr1c]

Posted this on 68kMLA too but I'll put it here for anyone reading just this thread:
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.

 

[Paralel]

I think I may have just come across a 540 screen that is unimpacted by tunnel vision. I ran it for slightly more than a hour, with the screen continuously on and displaying images, without even a hint of tunnel vision. Do you think this is a good enough test to declare it "unaffected" or should I run it for longer to see if I can cause it to manifest?

Posted this on 68kMLA too but I'll put it here for anyone reading just this thread:
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.

Sounds like a plan to me.

 

[3lectr1c]

I think i remember someone had it start after 2 or 3 hours so I’d run it longer. In my opinion though “unaffected” realistically means it doesn’t affect your use case, so if it doesn’t show up in the period you’re using it for, that’s good in my books. My 170 could start after 3 hours for all I know, never had it on for that long. I’ll have to test that.