When I turn it on the screen displays "no signal" then turns black. I've replaced the cords, switched the monitors but it still won't work.

Unplug all cables except for the power. ... Replace the side panel and screw(s), reconnect the computer cables, and turn on the computer. If the monitor still displays a black screen or displays a No signal message, the video hardware may be faulty and needs to be replaced or serviced.

Select Fn+ F4 (check 2 monitors) for check the change monitor . if not fix press with out FN.
if not fix go to display resolution and select dual display and duplicate .also select video dislpy LCD or VGA out to Both.
use user manual to more info

Here's some tricks I would try...
1. Verify the monitor's power cord is plugged firmly into the wall outlet and the back of the monitor.
2. Verify the monitor cable is firmly connected to the computer and the monitor.
3. Verify that you have turned the monitor power switch on.
4. If the power light on the monitor is not on, test the wall outlet (plug in a light or something you know works).
5. If the power light on the monitor is not on, try a different power cord.
6. If the power light is on and yellow or orange or flashing, but nothing displays, or the display is incorrect, borrow a monitor from a friend. If that works, your monitor probably needs replaced.
7. Also, you could try your display on a friend's computer. If it doesn't work, your monitor probably needs replaced. If it works properly on your friends computer, the problem may be with your computers video output port, motherboard video chip (or video card, if you have one), or drivers.

Good luck.

Here's some tricks I would try...
1. Verify the monitor's power cord is plugged firmly into the wall outlet and the back of the monitor.
2. Verify the monitor cable is firmly connected to the computer and the monitor.
3. Verify that you have turned the monitor power switch on.
4. If the power light on the monitor is not on, test the wall outlet (plug in a light or something you know works).
5. If the power light on the monitor is not on, try a different power cord.
6. If the power light is on and yellow or orange or flashing, but nothing displays, or the display is incorrect, borrow a monitor from a friend. If that works, your monitor probably needs replaced.
7. Also, you could try your display on a friend's computer. If it doesn't work, your monitor probably needs replaced. If it works properly on your friends computer, the problem may be with your computers video output port, motherboard video chip (or video card, if you have one), or drivers.

Good luck

1. Verify the monitor's power cord is plugged firmly into the wall outlet and the back of the monitor.
2. Verify the monitor cable is firmly connected to the computer and the monitor.
3. Verify that you have turned the monitor power switch on.
4. If the power light on the monitor is not on, test the wall outlet (plug in a light or something you know works).
5. If the power light on the monitor is not on, try a different power cord.
6. If the power light is on and yellow or flashing, but nothing displays, or the display is incorrect, borrow a monitor from a friend. If that works, your monitor probably needs replaced.
7. Also, you could try your display on a friend's computer. If it doesn't work, your monitor probably needs replaced. If it works properly on your friends computer, the problem may be with your computers video output port, motherboard video chip (or video card, if you have one), or drivers.

It's getting power, it's just not getting signal from the data cable. The cord that connects to the monitor, (not the power) is typically the reason it is going into standby mode. This can also happen if your graphics card driver is missing on your operating system, but you said you tried the monitor on another machine, so I narrowing it down to most likely be the data cable. Try another cable.

Replace your monitor power cord

Hello!

I see many monitor with that trouble.
When you turn on comp., you can have a picture on monitor about 10-30 min. and that go in black screen, or If you change resolution again go in black screen.
You must repair monitor or bay another.

chack your ram
your display cord may be damaged or loose chack it

My monitor does the same thing at times and sometimes shows "No Signal" and at other times the screen will maintain the images but the backgound color switches to mustard yellow. In each of these cases I have been able to solve the problem by unplugging the power cord from the electical outlet for about three seconds and plugging it back in. I have a KDS model 780 LCD.
GOOD LUCK