Five tips to fix a screen flicker
Aug 29, 2001
Bill Detwiler MCP
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© 2001 TechRepublic, Inc.


Few computer problems are more annoying than a flickering screen that appears to have no apparent cause but won't go away. TechRepublic member Nhughes recently asked for advice on such a problem in our Technical Q&A.

"Two of my users have reported that their screens flicker whilst they are working at their terminal," Nhughes writes. Nhughes also reports that the flickering is infrequent and the monitors sometimes flicker from the Windows desktop to a black screen. In some cases the screens even change color to a bright blue or pink. To help Nhughes and everyone else struggling with a maddening screen flicker, here are five tips to steady your screens.
Check the cables

When troubleshooting a screen flicker, I always check the cables first. Several TechRepublic members agree. Ian C B, Bruceb, Crjordan, and Aqmike all suggested checking the video and monitor power cables before doing anything else. Ian C B reminds us to confirm that the cables are screwed in tightly and to replace the cables with new ones to see if the problem persists.

"The color changes are almost always a faulty wire in the cable," Crjordan said. "Try working the cable back and forth near both connectors. If this causes the color change, you could have a broken wire in the cable, or a loose pin in one of the connectors. Make sure the cable is out of the way (from feet, hands, and other objects). You may also try zip-tying it to itself or another stable object until you can replace either the cable or the monitor."
Check the environment

If a cable isn't the culprit, then the user's workspace should be next on your hit list. Monitors are notoriously sensitive to magnetic fields. Speakers, florescent lights, fans, cell phones, radios, and any other electrical device can cause a wide range of monitor problems. (See Figure A.) "Check what's around the [monitors]," Vilefileman said. "Cell phones are known to cause screen flickers, among other things, and plugging a radio or fan into the same receptacle can also cause screen flickers."

Figure A

This fan is way too close to my monitor.

Bruceb wrote, "If the users are in cubes, check the other side of the cube to see if the next cube over has anything that could be interfering. I have fixed many a monitor by turning off a fan in the next cube. Also, we have some monitors that will cause monitors on the other side of the wall of a cube to degauss when they are turned on."

Check the display settings

Many computers that have been upgraded from Windows 95 or 3.x to Windows 98, NT, or higher experience screen flicker. This problem is often due to an improperly calibrated refresh rate. The refresh rate determines how often the computer redraws the image on the monitor screen. The Windows installation process, which includes selecting a video display driver, can occasionally select an inappropriate refresh rate for your monitor.

While the user can manually adjust the refresh rate, care must be taken to avoid harming the monitor. Excessively high refresh rates can damage certain video displays, so be sure to consult your device manual or the manufacturer's Web site before selecting the maximum possible refresh setting.

To manually adjust the refresh rate, click on Start | Settings | Control Panel and double-click the Display icon. Once the applet opens, select the Settings tab and click on Advanced. Select the Monitor tab. A drop-down list of refresh rates will be available here, and, provided you don't exceed the monitor's maximum rate, you can select each of these in turn to find the optimal setting (see Figure B). As a rough guide, refresh rates of 70 Hz to 85 Hz are common.

Figure B

Selecting the appropriate refresh rate for your monitor might be just the fix for a flickering screen.

Check the video card

Once you've checked the cables, environment, and display settings, it's time to examine the video card. Although rare, video card failures do occur. Open the PC's case, and first confirm that the card is securely seated on the motherboard. If it is, replace the card with one you know works. If the flicker disappears, you've found the culprit.

Check the monitor itself

If the flicker remains after checking the cables, environment, display settings, and video adapter, the problem may be within the monitor itself. "From the symptoms [Nhughes] describes, [the flicker] is probably due to dry solder joints on the CRT base (a small PCB on the end of the CRT)," said TechRepublic member Skutts, "If you, or anyone you know, are competent with soldering, then it should be a fairly simple task to re-solder these. A word of caution though—the CRT is essentially a huge capacitor with a charge of up to 25,000 volts. If you have no experience with electronics, don't take the back case off, send it away—a TV repairman should be able to fix it."

It was flickering a few minutes ago

While unlikely to be the culprit, there is one final possibility. If you haven't personally witnessed the problem, it may not exist. It is possible that the complaining end user simply wants a newer or larger monitor and thinks complaining about his or her existing screen will accomplish this. Combating such a fabrication takes creativity. I recommend giving the offending user a different monitor that you've been using as a spare. Clean it up and tell the user it's a newer model than the one they have. If you're lucky you can even find one that's a bit bigger than the one they had. Everyone's happy, and it doesn't cost a dime.