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PowerBook 170 Dark Corners

perez6991

perez6991

6502
I know this is a common issue with active matrix screens on the 170s but is there truly no way of fixing it? I recently just got a 170 and 190cs and they both booted right up. Would recapping effect the screen at all or is doing anything to the PowerBook even worth it at this point? I'll snap some pics later, although the darkening gets worse and worse slowly as the machine "warms up".

 
Sheesh, that bad huh? I guess I shouldn't have powered it on at all. It's getting worse with the machine powered off as well. Well at least I have one in my collection, who knew active matrix would've been plagued by this. At least my 190 is fine. Would a recapping guide be of any use to you guys? I can do both in separate threads if anyone is interested.

 
It really depends on how it was stored. I have seen a few Portables suffer from the same thing, but I have seen just as many that have not. 

But the ultimate cause is the actual liquid crystal has oxidized or contains moisture, causing impurities and this is the result. 

Eliminating the moisture contamination is the only way to fix it. 

 
I'm currently restoring a non-backlit Portable which has the worst case of moisture build up I've ever seen.  It starts up clear but after 10 minutes the screen is completely black.

 
I have a 540 wich is just like that.

Starting up fine with a nice sharp display developing a growing black border around the screen starting from the corners until it is totally black after a few minutes.

 
I have a 170 that has the dreaded tunneling problem.  Worried my other 170 will develop it some day too.

Has anyone encountered this phenomenon outside the world of Macs?

 
ooh maybe a hair dryer on low.. not too hot and not directly at the lcd.. just thinkin outloud.. that way you can control the heat..

 
Well I've noticed mine clears up pretty quickly (although only temporarily) from just leaving it in the sun and letting it warm up while it is turned off.

 
What's the humidity where you live? I live in a place with very low relative humidity and I just let it sit out on the table. Mine stopped "tunneling" (the informal name of the darkened corners phenomenon) entirely.

Just looked: humidity in my town is 17% right now. It's 50% in OP's location. It may need mechanical assistance of some kind. Sitting on top of a bed of rice in a box, or in a room with a de-humidifier, etc.

 
The average humidity here is about 70% so the atmosphere is basically soup year round. I bet this 170 wouldn't tunnel if I shipped it out west.

 
Wow it's down to 76% relative humidity here today. It's been at 95-99% for weeks. I'm glad I've managed to avoid any machines with moisture sensitive LCDs thus far!

 
Last edited by a moderator:
Well once you re-seal the panels back together (bad/shrunken seal) it wont do it again, AFTER you fix it...

Dry it out so it stops tunneling, and re-seal the glass. 

 
Well if anyone is interested on buying the 170 I've put it up in the trading post with a link to some pictures, alongside a Duo 230 and a 190cs.

 
you have to cure the issue first. Vacseal can work for the seal, may be a bit overkill but it will definitely seal it. 

 
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