LCD screen flickering badly, but only in Windows environment

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Hi - noob here, hopefully some can help me out. I've got a Compaq
Presario 2100 with a LCD problem. During boot up, the LCD seems fine
(maybe a little shaking/flickering) but after logging in, the LCD starts
flickering wildly, sometimes slowing or even stopping if a window is
open or a program. This is very repeatable. The external monitor port is
perfectly fine and I've even swapped out the motherboard with a old one
I had lying around (laptop fell on external ethernet card, breaking
port) and no change. I've also tried to repair Windows, which didn't fix
the monitor and seemed ******* things up on my computer (yay MS). I'm
going to do a fresh install of Windows when I get back from a buisness
trip but I don't think it will help. I've even tried adjusting the
refresh rate with no luck.

Assuming the software isn't the problem, do you all suspect the LCD
backlight or the inverter or something else? I can upload a video of the
problem if needed to youtube. Any help is appreciated. Thanks all.

Re: LCD screen flickering badly, but only in Windows environment

Are you using the native resolution of the LCD (1024x768 I believe)?

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Re: LCD screen flickering badly, but only in Windows environment

Andy_S wrote:
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You're not being clear.  It is either fine OR it's shaking/flickering.
Which is it?
What happens when you boot into the bios setup and let it sit.
Does it flicker there?
When it flickers, can you still see the text when the screen goes dark?
May have to use a bright flashlight set right on the display to see
the text on the screen beside where the light sits.
That will tell you if it's the backlight.
You can also look at a grazing angle into one of the edges to see if the
backlight is flickering when the display does.
When it's cold, does it start with a slight pinkish color?  That can be
a sign of backlight going bad.
Anything interesting happen when you flex the cable by moving the screen?

I'm not saying it's impossible, but I've never seen software cause
consistent screen flicker.  And if the vga port doesn't flicker, sw is
even less likely the problem.

If you bet the odds, you'd bet on a bad display cable.
Won't hurt to try replugging it.

but after logging in, the LCD starts
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Re: LCD screen flickering badly, but only in Windows environment

mike;494844 Wrote:
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Thanks for the reply. I checked the bios and no flickering or
distortion of the picture after one minute (the computer has been on for
a long time when I did this so no warm up issues). At the log in screen,
sometimes the sceen is perfectly stable, but sometimes it tweaks just a
bit (slight shaking of the screen and horizontal lines). When it
flickers I can still see the picture (no dimming or anything), however
there are some horizontal lines which are ******* up and are not
displaying the correct color information. I've tried playing with the
display cable with no luck (i.e. reseating the cable connector). Though,
previously, the display would act up (horizontal lines) and tapping on
the base of the laptop at the top where the speakers are located fixed
the problem. Though I don't if there are two problems here or one. The
resoution is set to 1024 x 768.

Also, dragging my mouse to the bottom right hand corner stops the
flickering. Sometimes the screen looks mostly ok though the black looks
pixilated and almost a purple color. Sometimes the screen is really
******* up (vertical ligter and darker lines with the picture looking
pixilated or chunky where the chunks are misaligned from each other).

Assuming that maybe the cable is bad, is it difficult to check the
cable with an ohmmeter? Thogh I assume the bad connection might only
occur under certain voltage loads so checking it that way might prove to
be difficult. If the fresh instal of windows doesn't work, I might just
go ahead and get a cable assuming it's not too expensive.

Re: LCD screen flickering badly, but only in Windows environment

Andy_S wrote:
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When we do remote diags, we try to come up with rational explanations.
I've exhausted all mine and am moving on to the bizarre.
It is possible for a ground trace to break such that the clock ringing
doesn't affect low-res/low clockrate modes but does cause problems at
higher resolution.  Ditto for corrosion causing the clock amplitude to
be low.  I once had a system where the pullup on the data line internal
to the chip was bad.
The chip could pull low, but not high, so there were bizarre,
display-content-dependent symptoms.

Try setting windows to the lowest resolution.
I can't come up with any possible explanation for why moving the cursor
to the corner stops the flickering.

There's always the possibility that it's malicious.  15 years ago, there
was a screen saver that looked like a corrupted display.  I would be
possible to write a display driver that messed up your display.
Can't imagine anyone going to that much trouble.
If you reload the OS, I'd FDISK and reformat the drive so you're
sure there's nothing malicious left.  Backup/restore methods differ in
how much old stuff they leave behind.

First thing I'd try is a linux live CD.

If that's bad, you have no choice but to shotgun the system a part at a
time.  Could get expensive.  Swapping the motherboard with an OLD one
was a good test, but there's the chance that something on the display
or cable hozed the graphics chip.  Wouldn't be the first time I took a
bad subassembly and a good subassembly and created two bad subassemblies.

Return address is VALID!

Re: LCD screen flickering badly, but only in Windows environment

Formatted the HD and performed a clean install of XP. The screen
twitched a few times during install so I was worried but since
completing installation and most of the updates, the screen has been
fine. Hopefully it stays that way.


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