Re: Repair LCD ghosts


"John Keiser" <john.keiser2@xxxxxxxxxxx> wrote in message
news:W7kkf.507$5V1.504@xxxxxxxxxxx
> Thank you for a great explaination. [I can now see the traces on the
> glass .. very faint]
>
> Any idea how to improve the "ghosting" - some of the digit segments appear
> very faded when they should be fully on or fully off.
>
> Thanks!
>
> --
> Remove -NOSPAM- to contact me.
>

Hi John

Have you considered that the problem may not be one of connection ? As these
displays generally employ matrixed drive for the segments, any problem with
the segment drive electronics, would show as bad segment contrast for the
same segment in all digits. Digit drive problems would show as all segments
being poor / missing in an individual digit.

Connection problems will show as digit-specific segment problems (
usually ).

Whilst the unit is apart, and powered, and showing its problem, you can try
applying gentle pressure along the connection edge to see if the symptoms
change. If they do, chances are it is a connection prob. If they don't, then
probably drive electronics.

Usually, the rubber connection sandwich, is reversible both ways- ie left to
right and top to bottom. Precise alignment is not usually an issue, because
of the comb pitch being much finer than the electrode pitch. You can try
reversing it either or both ways, and seeing if the symptoms change. If they
do, then the chances are that the sandwich is dirty or greasy - the chemical
structure tends to start to break down after some years, resulting in a non
conductive greasy film appearing on the surface. This is like when the
buttons on your TV remote get ' iffy '.

The sandwich is quite robust, and easily cleaned with isopropyl alcohol. If
reversing the sandwich changes the problem, or makes it worse, then the
chances are that the on glass contact fingers have been contaminated by
sandwich breakdown products. As I detailed before, you can clean the
electrodes with a cotton bud ( Q-Tip ) lightly moistened with IPA, but don't
go mad and scrub at them. A light pass, followed by letting it dry, followed
by a light polish with the dry end, will suffice.

Good Luck

Arfa


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