mono TFT edge-darkening discussion

[Dan K]

My apologies to folks who also read the PBs
list, but I figured this was relevant here
as well. The original discussion was about
Kai Steinmann's 540's mono TFT screen's 
darkening corners and edges:

I wrote:
>> I've got a _good_ Duo 250 TFT display
>> I'm going to try on my 2300, with which
>> a previous 280 TFT screen had done the
>> darkening corner thing.

then Tom Lee wrote:
> The gradual and nonuniform diffuse
> darkening that Kai's photo shows is 
> something else. I think that some months
> (maybe a year) ago, someone on this list
> offered his theory that there might be
> some contamination that poisons the liquid
> crystal material. If  bad seals are to
> blame, then it would make sense that the
> problem would first show up near the
> edges. Since Kai notices this darkening
> even with the backlight off, that theory
> might looks stronger.

Well, I had figured as much and my test,
while it doesn't actually confirm this, is
at least consistant with it. Since the
spread of the darkening is very 'organic',
that is, uneven and gradual, leaky corners
and edges seem as good an explanation as
any.

So last night I put my known-good mono TFT
Duo 250 screen on my 2300c, (see my quote
above), ran it continuously overnight and in
the morning was pleased to find it still
clear and non-darkened. As I say, this
doesn't prove anything, but does support the
idea that the screen itself is the problem.

I have a cracked :-( but still partly
working 280 screen (thanks Mad Dog! <heh heh>)
I'm letting run right now to see if it will
edge-darken. If it does I'll open it up
and see what there is to see.

Dan K