View Single Post
  #17   Report Post  
Posted to sci.electronics.repair
Cydrome Leader Cydrome Leader is offline
external usenet poster
 
Posts: 1,910
Default Bleeding LCD displays

Ian Field wrote:


"N_Cook" wrote in message
...
On 02/03/2014 15:41, Rich Webb wrote:
On Sun, 02 Mar 2014 12:55:11 +0000, N_Cook wrote:

Cause and any amelioration, short of draining the liquid and starting
again (for elfin safety in nothing else), and of course unobtanium
replacement displays

Where I used to work a batch of early large LCD display Philips DVM
meters for the engineers.
Every now and then , despite warning labels, someone would leave one in
direct sunlight (UK version)

heh

for a while and the display would become
next to useless, permanently.
Presumably the LC migrates out of its assigned wells and does not go
back in them. Anyone know of a localised heat/cold/pressure treatment or
something like that ,at least, won't make matters worse , and may
actually improve the splodge a bit?

That's been a problem with older LCD displays on Fluke DMMs as well.
My old 8050A is starting to exhibit those symptoms, despite having
been indoors all of its life.

It's ameliorated somewhat on mine when the display is energized for a
few hours; the dark areas retreat and become somewhat dimmer. Not a
permanent solution, but you might try that. Hook one up to an external
supply (they are battery powered?) and let it run over a weekend to
see if there's any improvement.

There are several hacks around the 'net where folks have replaced the
LCD module with a bank of 7-segment LEDs. What I'll probably try is to
fit an EADog 1x8 LCD module in place of the original, with a small
micro to handle the display initialization and character translation.
The EADog is 55 x 31 x 2 mm, a good fit for the 8050A.


This display is actually on a CD unit. Its not been used for some time so
may be what you say. Its also on the lower part of the display, perhaps
turning the CD upside down,


Once I repaired TVs for a back street bodger - a CTV came in with a rainbow
pattern on the picture and no amount of degaussing did any good. For some
reason I up-ended the TV, the picture improved a lot, so I turned it
completely upside down and the picture was perfect.

We took the CRT out and put it back upside down, then slackend the yoke
clamp and rotated that 180 deg, the purity rings needed a tweak but all was
well - so we wedged a lino tile between the anode cap and PCB to stop it
cracking over, and cased it up.


That reminds me of when people actually rebuilt or replaced picture tubes.
Any good stories of tubes imploding?