monitor image question

Can anyone tell me other than a defective monitor or video card what
else might cause my computer screen to collapse?
I have had the same computer and monitor for a couple of years now
(both bought brand new) and they have worked fine until recently. Now
after a few hours the screen seems to bend over on itself along the top
edge and sometimes even collapses to a bright horizontal line only a
few pixels wide across the center of the monitor. If I move my mouse
around I can see it moving in the squished image.
If I turn the monitor off and on again the picture does not restore.
If I reboot the computer it's ok again for a little while but after an
hour or so it will collapse.
So obviously a defective monitor right? Wrong. I have connected it to
another computer and it works fine. (The other computer is a laptop but
has the same screen resolution)
So obviously a defective video card right? Wrong. I went and bought a
brand new video card for my system and the problem still occured.
Anyone got a clue what else might be going on here? My only guesses
left are either the powerbar / power cable or maybe the motherboard? I
doubt it's the motherboard because the video card is what drives the
monitor not the motherboard, right?
In case people need machine specs:
Intel Pentium 4 2.4GHz with 1024 megs of RAM running Windows XP Pro
(SP2)
Monitor is a NEC Multisync FE991sb
Video card(s) are both nVidia GE Force, the original being a FX 5600
and the new one being a 5500 OC with both the latest drivers and even
with the drivers packed with both cards.

I'm out of troubleshooting ideas at this stage.

ComputerSpaceFan wrote:
> Can anyone tell me other than a defective monitor or video card what
> else might cause my computer screen to collapse?
> I have had the same computer and monitor for a couple of years now
> (both bought brand new) and they have worked fine until recently. Now
> after a few hours the screen seems to bend over on itself along the top
> edge and sometimes even collapses to a bright horizontal line only a
> few pixels wide across the center of the monitor. If I move my mouse
> around I can see it moving in the squished image.
> If I turn the monitor off and on again the picture does not restore.
> If I reboot the computer it's ok again for a little while but after an
> hour or so it will collapse.
> So obviously a defective monitor right?

Right! Almost certainly a poor solder connection associated with the
vertical deflection circuit. Such connections are subject to the
expansion that heat makes on the PWB or a vibration. Turning off the
monitor for a few moments may be enough to cause it to make connection
again. If you want to explore this theory, whack the side of the
monitor while it is failing. It might restore the vertical momentarily.

I guess it could also be a bad conductor in the video cable for the
vertical sync, but I would go with the solder connection particularly
since your monitor is a couple of years old.

Wrong. I have connected it to
> another computer and it works fine. (The other computer is a laptop but
> has the same screen resolution)
> So obviously a defective video card right? Wrong. I went and bought a
> brand new video card for my system and the problem still occured.
> Anyone got a clue what else might be going on here? My only guesses
> left are either the powerbar / power cable or maybe the motherboard? I
> doubt it's the motherboard because the video card is what drives the
> monitor not the motherboard, right?
> In case people need machine specs:
> Intel Pentium 4 2.4GHz with 1024 megs of RAM running Windows XP Pro
> (SP2)
> Monitor is a NEC Multisync FE991sb
> Video card(s) are both nVidia GE Force, the original being a FX 5600
> and the new one being a 5500 OC with both the latest drivers and even
> with the drivers packed with both cards.
>
> I'm out of troubleshooting ideas at this stage.
>