strange display behavior...any ideas?

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Hi all,

I have a strange display weirdness happening--lots of little red sparklies
in the dark areas of my lcd monitor. Yes, that just looks like a failing
graphics card or dirt on the contacts, but the provenance is what is

This monitor is new, an LG 22" LCD. I was running with an old 21" CRT for
years with no problem. When I hooked up the new monitor everything looked
good--for about one day. Then on one startup I noticed little red dots all
over the place--this happened from the beginning of  the POST boot, so it
may not be a graphics card problem. But anyway I have another graphics
card--a pretty decent NVidia Quardo FX pulled from a workstation (AGP 8x).
Installing that seemed to solve the problem, so I just left the old card out
(ATI 9600) and ran with the NVidia card.

And it worked just fine, for two days. Now suddenly I am getting the same
red sparklies as I had with the ATI card--exactly the same. I tried cleaning
the contacts and used some cleaning spray (Electrolube Preclene) on the AGP
socket contacts. No change. The card has two outputs--tried both. Same same.

But if I hook up the old CRT monitor everything looks fine! No problem at
all. I am hooked to the same DVI-D input as with the LCD monitor via an
adapter to 15 pin VGA

I have brought the LCD monitor and hooked it up to my other computer. It
also looks fine--so far...

So does anybody have any idea what might be going on? Does this sound like a
monitor issue, and if so, why does it only show up after a certain amount of

Any light that anyone can shed on this mystery would be greatly appreciated.



Re: strange display behavior...any ideas?

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Keep an eye on the monitor (on the alternate PC) as it could be a
faulty one.

Re: strange display behavior...any ideas?

Toby wrote:
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"Sparklies " indicate transmission errors on the red channel. It means either
the bandwidth of the video card red channel is too low, or too long a
cable is being used. If you used a high quality DVI cable, to connect
the monitor to the video card, the sparklies may just disappear.

The transmission path looks like this -

     GPU ------ connector ----------- DVI_cable ------- connector -----

Any of those items in the path, could be degrading the signal. By switching
video cards, if you got a different result, then the GPU would be
partly responsible. Since it seems to be getting worse with time,
it could actually be a problem with the chip in the LCD_monitor
end of things.

In the lab, engineers check the signal quality, with
an "eye diagram". The signal is not allowed to touch
the three, dark blue areas on the digital scope display.
When the signal touches the blue area, then it may be
possible to see Sparklies (it all depends on how much
better than the DVI spec, that the RX chip is).,931-19.html

You can cause Sparklies on any DVI setup, if you use a long
enough cable. As the cable gets longer, the signal droops
into the blue. Or an attempt to "split" the signal, might
also give lousy results (I think there are people who sell

So, there remains the question, as to which component in the
above interconnect, is having the largest effect. There
are some pretty cheesy cables out there. But it could also
be a problem with the monitor, and its TMDS receiver chip.

Your VGA connector, uses a different path and a different
method than the DVI. The VGA is analog, and when it goes
wrong, the picture gets waves or reflections or blurriness
in it. And possibly for all  the same reasons (crappy cable,
bad connectors, weak GPU etc). A long VGA cable may only
give a clear signal, at a reduced resolution, like
1024x768, so both technologies have their limits, when
it comes to cabling.


Re: strange display behavior...any ideas?

Thanks Paul, that's very helpful information. So far I am having no problem
using the same cable on my other computer, but it also has a new and pretty
powerful VGA. The cable appears to be decent, but perhaps I will try a
different one on the computer with the problem.


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