Cause: The brightness and contrast settings may not be set correctly. The CRT may be wearing out.
Solution: Check the brightness and contrast settings. As the CRT ages, the screen will start to dim. In some cases, your repair shop may be able to tweak the monitor to improve the brightness. Change the lighting in the room so that there is no direct light falling on the monitor. Turn off the monitor when not in use. In any case, this might well be an indication of age catching up with the monitor—time to go shopping!