Configure the operating system
Since monitors with cathode-ray tube was provided for screen auto off after some time of inactivity the system. It had to burn-out of CRT phosphor under the influence of electrons. LCD monitors burning is not threatened, but the screen dims to save power.
You can change the time of screen blanking. Right-click the mouse on the empty space of the desktop and choose "Properties" command in the context menu. Go to the tab "screen Saver" and press the "Power" in the section "Energy efficiency". In the dropdown list "display" specify the time of inactivity after which the monitor will be turned off.
A technical fault
If you disconnect the monitor occurs during "heavy" games or working with 3D graphics, you may have a problem with the video card, especially if on the screen appear smaller artifacts, like dead pixels. Unplug the system unit from the power supply, remove the side panel and carefully remove the graphics card from the slot. If the card has a fan, remove the dust with the vacuum cleaner. The connector for the video card, wipe the eraser to remove the oxides. Gently insert the card into the slot and test the monitor.
Try replacing the interface cable from the monitor to the system unit – malfunction can also cause disconnection. Insert the cable tight, as the cause of trouble may be a bad contact. Connect the monitor to the system unit with the power supply disconnected.
Modern video cards consume a lot of electricity. Perhaps your power supply cannot cope with the load, especially if it is older than 3 years. Replace with a more powerful PSU or test the card on another computer with obviously a more powerful power supply. Program Everest or a similar view of the temperature of components inside the system unit – perhaps outages happen due to overheating.
Download on the website of the manufacturer of your video card new driver and install. If shutdown has not stopped, connect the monitor to another computer to verify the source of the problem.
With the demise of the screen and try several times to turn on / off the monitor's power by the Power button. If the image will be the source of problems in the food chain – as a rule, dried up or swollen capacitor. This technique will not help, if the failed backlight lamp or the matrix monitor.