If your computer screen is flashing on and off, it could be an indication that the monitor is failing. Some computer settings, however, can cause the monitor to flicker or turn off. Windows 7 automatically turns off the monitor after a set period of time, and certain screen settings can produce a repetitive flash. The screen may also flash on and off if the power or data cable connections are loose.
Click the battery icon found on the far right of the taskbar. Click "More Power Options."
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Click "Choose When to Turn Off the Display." Change the drop-down menus next to "Turn Off the Display" to "Never," then click "Save Changes."
Hold down the Windows logo key, then press the "D," to go to the desktop. Right-click the desktop, then click "Screen Resolution."
Click "Advanced Settings." Go to the "Monitor" tab then select a refresh rate in the range of 72 Hz to 85 Hz. Click "OK" twice.
Press the power button to turn off the monitor if the problem continues to occur. Check the power cable connected to the back of the screen. If the power cable is loose, push the connector into the power slot on the back of the monitor until you meet resistance.
Confirm the other end of the power cable is completely connected to the outlet. If the power cable is connected securely to both the outlet and the monitor, but the screen continues to flash on and off, use another power cable to test if the issue is related to the cable itself.
Check the cable connection on the back of the computer and on the back of the monitor. Reconnect one end of the video cable to the back of the monitor, then tighten the thumbscrews in place. Reconnect the other end of the video cable to the back of the computer, then tighten the thumbscrews. Replace the video cable if the problem continues.
Check the indicator light when the monitor flashes off. If the indicator light is flashing green or glowing amber, the problem may not be the screen, but the computer. Disconnect the video cable when the monitor flashes off; if a message such as "No Signal Could Be Found" appears on the screen, the video adapter could be at fault. If the indicator light is off, then the monitor is most likely defective.