when the computer is turned on, the display is not lit, which can be divided into two situations: the display is not powered on (the power indicator is not lit) or powered on (the power indicator is lit) but there is no sighal or the screen displays "no sight al". The former means that the circuit is blocked, or the power interface or power cord is poorly contacted or damaged, while the latter generally means that the memory bar is loose or oxidized, or the data cable of the display is poorly contacted, or the memory, graphics card, display or data cable is damaged. Suggestions: 1. If the monitor is powered on but shows no signal, turn it off (if the power switch is not effective by short pressing, press the switch for a long time until the power indicator light goes out or directly unplug the power cord), turn off the power and open the case, plug and unplug the memory module again, and wipe the golden finger in one direction with a rubber (scraping the thumb and fingernail back can also be done). If possible, install it in different memory slots, and then turn it on after installation (before operation, you should touch the wall with your hands to release your own static electricity or wear anti-static gloves). If you can't operate it, it's simpler: just slap or kick the chassis once or twice (note position: the right center of the left and right housings of the chassis with no interface at the back; Attention: don't push too hard, of course, you can't be weak. The above operation may need to be repeated. If it fails, the memory module needs to be replaced. If there are more than two memory banks, you need to test them one by one. 2. If the above operation fails, turn off the power and turn on the chassis, plug and unplug the graphics card again, and plug the data cable between the monitor and the graphics card tightly. If it still doesn't work, consider that the data cable or graphics card is damaged, and then replace it with a new one. 3. If the monitor is not powered on (the indicator light is off), first check whether the power switch is turned on, then check the back of the monitor, plug the power cord connected to the monitor up (the power cord can be replaced if possible), and check whether the other end of the power cord is powered on to the socket. 4. If the host computer can display when connected to other monitors, or the local monitor cannot display when connected to other normal hosts, it means that the monitor is damaged and needs professional maintenance.