26 Jul
2013
26 Jul
'13
10:33 p.m.
I have just pulled a heap of old Apple PowerBooks and Newtons out of
storage, and have discovered that quite a few of the LCDs that were
perfect last time I looked at them (some probably not for seven years
ago now) have deteriorated to the point that they are no longer usable.
Problems vary from big black splotches on mono screens, to colour
screens with almost the entire display from the centre out showing only
the backlight.
For monochrome LCDs, a black splodge genrally means the liquid crystal
material has leakced out. Rememebr that there are corssed poalraising
filters o nthe sides of hte display and that the unenrgized state of the
liquid crystal is to rotate the polarisation of light by 90 degrees. So
that an unergized dispaly transmitls like (looks 'light') but if the
liquid crystal material leaks out, you are essentially lookuing trhoug
corssed polarising filters with nothign to rotate the plane of
polarisation, so it looks black.
As yo waht caues it, damage to the seals between the 2 layers of glass. I
susepct heat or mechanical shock is a common cause of this damage.
-tony