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Monitor or Video Card problem? Can't tell.

Last response: in Graphics & Displays
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March 23, 2010 12:20:40 PM

In the past few weeks a strange problem has developed on my desktop. I'll be working along on my ViewSonic 22" LCD display, powered by a single XFX Radeon HD4650 and all of a sudden certain sections of the screen will display as strange sort of visual "noise". It almost looks like the moire patterns that we used to see on maladjusted CRT monitors. Certain colors or backgrounds will get "fizzy". I'm sorry I don't have a more precise vocabulary to describe the problem. Then, it will go away and not come back for hours.

I'm using Windows XP on an i5 system and it's been rock stable since I built it around Christmas. The power supply is plenty strong (800w). I updated the Catalyst driver and I didn't see the problem for several days, and today it's back.

I checked the connections, even looked around for any sources of RF noise or electromechanical devices causing "interference". If I didn't know better (I think) I would think that this disturbance was caused by sunspots or something.

I don't even know if the problem is with the monitor or graphics card. The monitor is 2 years old and has never exhibited any problems. The 4650 is about 6 months old.

Thank you.

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a c 147 U Graphics card
March 23, 2010 12:31:46 PM

You could try the following.

- replace video cable
- If the 4650 has 2 DVI connections you could try using the 2nd DVI connection
- Try using a VGA cable to the LCD (if your 2nd port on the 4650 is not VGA you will need to use the adapter that should have come with the card)

We basically have to narrow down if its the LCD,cable, or card. I don't suppose you have another lcd laying around or another card? Or another machine to use the lcd on for a while and see if the issue crops up? Just thoughts that I had.
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March 30, 2010 12:53:17 AM

jay2tall said:
You could try the following.

- replace video cable
- If the 4650 has 2 DVI connections you could try using the 2nd DVI connection
- Try using a VGA cable to the LCD (if your 2nd port on the 4650 is not VGA you will need to use the adapter that should have come with the card)

We basically have to narrow down if its the LCD,cable, or card. I don't suppose you have another lcd laying around or another card? Or another machine to use the lcd on for a while and see if the issue crops up? Just thoughts that I had.


Thanks for your suggestions. I've switched connectors on the card and I didn't have the problem for a week. Then last night, I switched off the monitor instead of letting the power management black it out like I usually do, and this morning I saw the problem again.

I've ordered a new cable that should be here in a few days. I want to see if that's the problem.

One thing I noticed about it, though: When the problem does occur, it seems to come and go as I move the mouse across different elements on the desktop. For example, I notice the problem most across the little gradient background behind the tabs on my Mozilla. When I mouse on, the "noise" occurs. When I mouse off, it goes away. Strange.
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April 9, 2010 2:33:26 PM

I believe I have narrowed the problem down to when my antivirus program is doing one of its periodic scans, and only when it's scanning a particular hard drive.

Is it possible that one of my older hard drives (I've got 4 in this machine) is putting out some RF or other electronic "interference" that is being picked up somewhere along the video subsystem?

I think I might have to chalk this one up to "gremlins" and just live with it. I've tested the monitor and the video card on other systems and have not seen this problem. Since it only occurs about once a week, and then only for about 5 minutes, I guess I can live with it.
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April 9, 2010 2:34:20 PM

Best answer selected by waxwing.
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