This will prevent possible damage to delicate electrical circuits on the motherboard, expansion cards, and memory chips. Disconnect the computer from its power source. You should unplug the cord from the computer. If you only unplug the cord from the wall outlet, someone else may accidentally plug it in without your noticing. By unplugging the cord from the computer, you will lessen the chances of power being accidentally restored to the computer while you are working on the machine.
Monitors contain a seriously dangerous, potentially fatal charge.
It is not recommended that anyone without pr oper training and equipment attempt to open and repair a defective monitor. If your machine is not operating normally, restart the machine. This sometimes corrects the problem. Make sure everything is plugged in and turned on. Check all cable connections and switch settings.