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Troubleshooting Video

Figure 3.8 depicts the components associated with the video display. As the figure indicates, in the case of hardware problems, the components involved include the video adapter card, the monitor, and, to a lesser degree, the system board.

Figure 3.8Figure 3.8 Video-related components.

Common symptoms associated with display problems include the following:

  • There is no display.

  • The wrong characters are displayed onscreen.

  • Diagonal lines appear onscreen (no horizontal control).

  • The display scrolls (no vertical control).

  • An error code of one long and six short beeps is produced by the system (BIOS dependent).

  • A CMOS Display Mismatch—Failure to Verify Display Type error displays.

  • An error code of one long and two short beeps indicates a display adapter problem (BIOS dependent).

  • Characters are fuzzy.

  • The monitor displays only a single color.

Video Hardware Checks

The video monitor should come on fairly soon after power has been applied to it. With newer monitors, the monitor is normally only asleep and is awakened through the video adapter card when power is applied to the system. When the system is shut down, the monitor's circuitry senses that no signal is present from the video adapter card and slips into a monitoring mode as long as its power switch is left in the On position.

If the monitor does not wake up early in the system's startup process and present a display, you should assume there is some type of hardware problem—the bootup action and operating system have not been introduced to the system before the single beep tone is produced. However, video problems that occur after the single beep are more likely to be related to operating system configuration settings.

Check the monitor's On/Off switch to see that it is in the On position. Also, check its power cord to see that it is either plugged into the power supply's monitor outlet, or into an active 120V (AC) commercial outlet. In addition, check the monitor's intensity and contrast controls to ensure that they are not turned down.

Determine which of the video-related components is involved. On some monitors, you can do this by just removing the video signal cable from the adapter card. If a raster appears onscreen with the signal cable removed, the problem is probably a system problem, and the monitor is good. If the monitor is an EPA-certified Energy Star–compliant monitor, this test might not work. Monitors that possess this power-saving feature revert to a low-power mode when they do not receive a signal change for a given period of time.

Exchange the monitor for a known-good one of the same type (that is, VGA for VGA). If there is still a video problem, exchange the video controller card with a known-good one of the same type.

Other symptoms that point to the video adapter card include a shaky video display and a high-pitched squeal from the monitor or system unit. If the system still does not perform properly, the source of the problem might be in the system board.

If you can read the contents of the display through the startup process, but then cannot see it after the system boots up, you have an operating system-related video problem. If the Windows video problem prevents you from working with the display, restart the system, press the F8 function key when the "Starting Windows" message appears, and select the Safe Mode option. This should load Windows with the standard 640 x 480 x 16–color VGA driver (the most fundamental driver available for VGA monitors), and should furnish a starting point for installing the correct driver for the monitor being used.

After you have gained access to a usable display, check the installed video drivers. You can access the Windows video information through Device Manager. From this utility, select the Display Adapters entry from the list and double-click the monitor icon that appears as a branch.

The adapter's Properties dialog box should open. The Driver tab reveals the driver file in use. If the video driver listed is not correct, reload the correct driver. Selecting the Resources tab displays the video adapter's register address ranges and the video memory address range, as shown in Figure 3.9. You can manipulate these settings manually by clearing the Use Automatic Settings check box and then clicking the activated Change Settings button. You also can obtain information about the monitor through the System icon.

Figure 3.9Figure 3.9 Video adapters resources.

You can also gain access to the Windows video information by double-clicking the Display icon found in Control Panel. Of particular interest is the Settings tab. In Windows 95, the Change Display Type button on this tab provides access to both the adapter type and monitor type settings. In Windows 98 and Windows Me, the Advanced button on the Settings tab provides access to both the adapter type and monitor type settings through the Adapter and Monitor tabs.

In Windows 95, the Adapter Type window provides information about the adapter's manufacturer, version number, and current driver files. Clicking the Change button beside this window brings a listing of available drivers from which to select. You also can use the Have Disk button with an OEM disk to install video drivers not included in the list. You also can alter the manner in which the list displays by enabling the Show Compatible Devices or the Show All Devices options.

In Windows 98 and Windows Me, the information about the video adapter card is located on the Adapter tab. Clicking the Change button on this tab produces a wizard that guides the process for changing the drivers for the card. The first option provided by the wizard is to allow Windows to search for the correct driver, or for the user to specify a driver from a list of available drivers. You can also use the Have Disk button to install video drivers from an OEM disk.

If the video problem disappears when lower settings are selected, but reappears when a higher resolution setting is used, refer to the Color Palette box on the Display Properties, Settings tab, and try the minimum color settings. If the problem goes away, contact the Microsoft Download Library (MSDL) service or the adapter card maker for a compatible video driver. If the video problem persists, reinstall Windows. If the video is distorted or rolling, try an alternative video driver from the list.

Some display problems might be caused by incorrectly set front panel display settings. The monitor's front panel controls (either analog or digital) establish parameters for brightness, contrast, screen size and position, and focus. Typical problems associated with these controls include fuzzy characters, poor or missing colors, and incomplete displays.

Actually, there can be several causes of fuzzy characters on the display. The first step in checking out this problem is to reset the display resolution to standard VGA values. If the fuzzy characters remain, check the intensity and contrast controls to see if they are out of adjustment.

Finally, you might need to remove built-up electromagnetic fields from the screen through a process called degaussing. This can be done using a commercial degaussing coil. However, newer monitors have built-in degaussing circuits that can be engaged through their front panel controls. These monitors normally perform a degauss operation each time they are turned on; however, sometimes the user might need to perform this operation.

The front panel controls can also be used to adjust the Red/Green/Blue color mixture for the display. If the monitor is showing poor colors, or only one color, examine the color settings using the front panel controls. If these settings are responsive to change, the problem exists in either the video adapter or the signal cable (broken or bad pin or conductor) or the monitor's color circuitry is deteriorating.


You should never remove the outer shell from a CRT video monitor unless you are trained to work inside the case and it is part of your job. There are very lethal voltage levels (in excess of 25,000 volts) inside the monitor that can remain stored there for some time. Even if the monitor has been unplugged for some time, it can still kill or severely injure you.

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