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haemogoblin

General question about B/W Powerbooks and their screens

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I couldn't think of a more suitable place to post this, though I did consider posting it in the lounge.

 

As someone who owns a letter boxing Powerbook, I was wondering if there are any black and white / greyscale display Powerbooks that dont suffer from this dreaded affliction.

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I believe it has been established that this is related to moisture entering the screen.

 

I have a 180 that had it directly after being shipped to me from the US east coast, and after sitting out and about in my house in the dry intermountain southwest region, it no longer does this.

 

(It is not "fixed" as much as that it's not in an environment where this can happen, although I think there was talk about what it would take to re-seal the display, I don't remember what came of that.)

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Unfortunately I live in the North of England where the weather tends to change for much of the time. Its never constantly warm and dry, so my PB is unlikely to 'dry out'. I had it sitting in the airing cupboard for two months and it still letterboxes in the same bottom right corner.

 

So I was curious if there were any other mono display PowerBooks which didn't suffering from it.

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My apologies, I mis-read the question.

 

My understanding, possibly wrong, is that this is a problem with the active matrix displays, so older and lower end machines (140, 145, 145B, 150) won't do this, but I don't know if it's worth downgrading to that display.

 

If you have some way to dry out the display, such as by putting it in with some rice or another desiccant, then it might be better to do that than to swap the display with that from another model.

 

It doesn't need to be hot and dry, it can be cold and dry when this happens as well, air conditioners tend to dry out environments, for example, if you have an air-conditioned workplace/office you can leave the machine.

 

Once the display is  dry, I believe there has been talk about ways to re-seal the panel so it doesn't get moisture in it again, but I don't know where you'd need to do it and what would be the best way to do this.

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Isn't it also failure of CCFL backlighting and (in some panels) capacitors? A couple of members reported using a replacement LED strip for backlighting, but this and cap replacement I've never heard if it fixes the vignetting permanently.

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So the screens that really suffer from this are the active matrix screens. They're not well-sealed, so moisture gets in and causes the vignetting.
Caps around the screen definitely do need to be replaced, they're likely leaking. Not really a cause of the vignetting, but it may cause other issues (and a dead screen).
CCFL failure would look kind of the opposite, light on the edges and dark in the center.

Some people bake the screens on a low heat to evaporate the trapped moisture, and then re-seal the screens.
You can use rice, or silica balls as a dessicant, or any other atmospheric dessicant in a small sealed box with the screen, and check it after a few days or so.

Passive Matrix LCDs don't suffer from this issue, but they also aren't anywhere near the quality of the active-matrix models.

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The 140, 145, and 160 don't have this issue, just the leaky capacitors that need to be replaced.
Image quality overall on those is quite a bit lower than the active screens, though. I'd love an active matrix screen on my 160.

I've seen some use various sealants to re-seal the screens after drying, but don't know offhand unfortunately.
If you search around the forums, this is not an uncommon discussion, and I'm sure someone has mentioned what sealant they used.

Edited by Rajel

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The cheapest bulk dessicant you can get easily is crystal kitty litter.  It's the same as the stuff in those "Do Not Eat" dessicant packets in pill bottles.

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