To troubleshoot monitor problems, start by checking for properly connected power cables, then switch the monitor and the system off and then on again. Also, confirm that the video adapter is configured correctly for the display. If possible, try the monitor on another working system (or a functional monitor on the potential problem system) to determine if it's an issue with the monitor or the system itself.
If the problem persists, the next steps depend on the type of monitor, and the problem experienced. Common CRT monitor problems include no image displayed, image flickers, scrambled image, CRT emits a loud squeal, or it only shows a thin horizontal line in the middle. If no image is displayed, ensure the contrast and brightness settings are set to mid-range. If the monitor displays only a thin horizontal line in the middle, discard it.
Common LCD problems include showing no image, screen flickers, an unstable screen, poor image and a message that signal is out of range. If the LCD shows no image even after basic troubleshooting, disconnect the system signal and power the LCD alone. It should show some light or display a "No video" message. If it supports signals from multiple sources, select the appropriate source from the menu. If the problem continues, contact the LCD manufacturer for technical support.