Re: Display problem that I can't grok
- From: Kevin ashley <kevin_news@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 04 Apr 2007 21:55:25 +0100
Fixer wrote:
Ok first thing to do is to connect the laptop to an external monitor, now if the problem persists on the external monitor you know its the graphics card ar fault and you need to replace either the graphics card if its an add on or the worse case scenario is the motherboard , now if the display is ok on the external monitor then try reseating the flex cable at both ends of the LCD (Panel and motherboard) if that dont work replace the cable its self or if that fails to work then you need a new LCD panel.
Unfortunately it isn't straightforward for me to get the laptop
to my place where I could try out the external monitor solution.
If there's a board failure or a panel failure it probably isn't
worth us fixing. I was hoping someone might be able to explain a
failure mode which would cause these symptoms, since my understanding
of graphics hardware (which admittedly is fairly out-of-date, and
mainly related to systems driving CRTs) can't explain this happening
when using direct colour, as opposed to some colour-map scheme.
I've heard that LCD panels do actually have to dither from true-colour
RGB triples since they can't actually display 255 different brightness
levels for each of R,G and B. If this is the case, then some failure
at that stage might explain it.
Thanks for the detailed reply anyway, and sorry to all it's taken this
for me to get back and follow up on these - was unexpectedly away
from net access for some days.
"Kevin ashley" <kevin_news@xxxxxxxxxxxxxxxxxxxxxx> wrote in message news:460e58c0$0$764$5a6aecb4@xxxxxxxxxxxxxxxxxxxx.A friend asked me to help after 'their laptop screen turned red',
and it turned out to be a more subtle problem which I confess I
can't diagnose at all. I'm hoping someone can shed some light
on the cause, and speculate as to whether it's likely to
get much worse in the near future.
The problem is that certain colours - primarily shades of dark
blue, but also a few others - are all being displayed as the
same shade of solid red. It's very noticeable on the bootup
screen, whose background changed from dark blue to solid red.
On the desktop, it's noticeable as a sort of red dust around
icons and text, and a change in the colour of window bars (usually
blue.) The effect can be seen more clearly in Windows XP by
bringing up any of the menus which allows you to choose an
arbitrary colour by moving sliders. These tend to display
a complete continuous colour map, and one can see speckles
of red in the centre of the dark blue area, and a few
elsewhere.
It's as if a small percentage of R,G,B values are being mapped
into solid 255,0,0 by something in the display hardware.
The problem seemed to come on all at once, and hasn't got worse
in 3 weeks or so. The machine seems usable for most stuff
except photo and video processing as long as you avoid
blue-heavy colour schemes.
I'm not really expecting that this is sensible or even possible
to fix in a laptop, but I would like to understand what is
going on, and whether it's likely to get much worse in the near
future. Anyone recognise the symptoms or cause?
TIA
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