Help needed with identifying cause for dirty white illumination in LCD monitors. Looks yellowish / o

Hi,
I am just getting into LCD repairs and I have a batch of liquidvideos
L17LCD2's .. They all seem to exhibit the same picture quality when it
comes to the whites!.. All display an off white with or yellowish
tint instead of a clean white background. I am unable to adjust it
out in user settings. Before I order new ccfl lamps I want to be sure
if what I'm experiencing is a common symptom of the lamp starting to
go. Want to be certain it's just not inherent to cheap LCD monitors.
Could even the filters be yellowing for some reason perhaps? Thanks
for any insight!
Chad.
www.arcadecup.com

 

It's the lamps.

But think twice about getting into replacing CCFL's. Often they're
buttoned up under layers of covers, tape, aluminum tape, and glue.
They're about as fragile as a supermodel's marriage and emit a few
milligrams of mercury vapor when you break them. And you will break
them, both old and new, until you get the technique right. It takes
the steady hands and sharp eyes of a surgeon to R & R these and get a
good outcome.

 

It depends, some are very easy to replace, others are nearly impossible.
Pull the lamps out of one of the monitors you have first to see if it's
something you want to do multiple times. Also at that time you can power it
up and verify that the lamps are in fact off color. It is possible though
unlikely that the plastic light guide or reflector has yellowed from the UV
or heat.

 

What environment were they operated in?
Cigarette smoke/nicotine?

Deke

 

In some cases, I think that it's just inherent in LCD technology. I am
currently watching this on an HP 19" widescreen monitor which is perhaps 3
months old. Not a cheap or poor quality 'no name' unit. I am using Outlook
Express with a full white background. To the average eye, it looks very
good, and I'm pretty sure that most people would struggle to find anything
wrong with the picture, but if you really want to get pedantic about it, the
far left and right sides of the screen are definitely not as white as the
centre - unless you move your head right in front of those areas, at which
time, they become brilliant white, whilst the opposite side, which you are
now looking at from an even more oblique angle, becomes a little worse. Even
though these days, LCD viewing angles are quoted at 160 deg or better, I
find that the *optimum display quality* viewing angle, is rather less than
that, for just the sort of reasons you are describing. Do your yellow
patches vary with viewing angle ? That might perhaps give a bit of a clue as
to whether it is a genuine problem, or just 'the way it is'.

Arfa

 

Cool thanks guys... yes I already did some dry runs removing the bad
bulbs... They do snap very easy very fragile and delicate process
indeed. Just getting to them the first time was a task. removed the
end caps also no problem. Wow the housings for the lamps are actually
yellowed pretty bad... the rest looks great such as the plexi panel,
sheets, white sheet. is it possible that the small amount of space the
yellowed case for the lamps takes up would be the cause?.. Anyone have
any tips on what to use to recolor these white and see if that makes a
dif? I suppose I will find something temporary for now... If it's the
cure I would like something that will hold its white under heat and
reflect decent...

 

I gave a 15" Sylvania (Funai) LCD TV to my girl for her bedroom and it has
always had a yellowish cast on whites. I agree with you that it may be
inherent in some but no all cases. I'm using a Dell 19" LCD that is maybe
2 years old and the whites on it are very white and equal across every mm
of the screen. I'm very happy with it so much that I bought another for a
spare.