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[ The PC Guide | Troubleshooting and Repair Guide | The Troubleshooting Expert | Troubleshooting Specific Components | Troubleshooting Monitors | Failure or Improper Operation ]

The video output is scrambled on the screen, the picture appears to be a tight mass of diagonal lines moving around

Explanation: There appears to be a signal from the PC, but the picture is scrambled or wavering a great deal. The image cannot be viewed clearly.

Diagnosis: This sort of image problem can be caused by incorrect driver or refresh settings, or by a problem with the monitor itself. Note that occasional waves on the image are usually a different problem.


  • A common cause of this sort of image difficulty is trying to drive a monitor with a refresh rate or resolution that is too high for it. If the symptoms only occur when in Windows but not when booting to DOS, for example, this is likely the problem. Try resetting the resolution and refresh rate to lower values and see if the problem goes away. In Windows 95, you may want to hit {F8} while booting and boot into Safe Mode, which will start the system with a simple driver, low resolution and low refresh rate, and then adjust the system settings and reboot normally.
  • Check the image size and positioning controls on the monitor. If the image is made too large or is shifted too far in one direction on the screen, this can cause the monitor to incorrectly display the image. Try all of the various size and position adjustments to see if you can get the image to stabilize.
  • Troubleshoot the monitor.
  • Make sure that you are using the correct drivers for your video card.
  • Troubleshoot the video card.

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