Plug to monitor came off

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.

Did you tried changing the lcd settings to default?

You would need to power cycle your monitor. You can do this by unplugging it from the wall for 30 seconds. Than plug it back into the wall and press the power button.

This has worked three times on a Dell PC: shut down; turn off monitor and PC at wall socket, unplug wall sockets, wait 30 seconds, plug back in to wall socket or power board, turn on, all should be well?

First attempt to use a different monitor on your computer, or use this monitor on another computer. If it appears that monitors only shut off when attached to your computer then it's safe to assume that you have a graphics card issue, not a monitor issue. If your monitor shuts off on another computer then your monitor is basically broke. To try to troubleshoot the graphics card, unplug your monitor from the computer and the wall. Now unplug your computer from the wall, open up your computer case and remove the graphics card. Using a can of compressed air, blow out all of the dust in the computer. Reinsert the graphics card, close the case, plug the monitor back into your computer and the wall and start the computer again. Hope this helps.

1. Make sure that the monitor is turned on and has power. Make sure that the display's power cord is plugged into a working wall outlet, and that it's properly connected to the power adapter. (To check if the wall socket is working, plug in a lamp or other electrical device.)
2. Check that all video cable connections to the computer video port and to the monitor are properly connected.
3. Examine the pins on the video cable connector to make sure they are not bent or damaged in any way.
4. Connect a known working display (if you have an extra one available). If you see video after doing so, replace your old display.
5. Unplug the video cable and then turn on the monitor, check any message is showing in monitor if its shown means ur monitor is ok or else their is a problem in monitor..
6. turn off the system and check the ram..
   
7. Reset the computer...

Switch off power at wall,open h/drive case and visually check that
connection to monitor has not partially come adrift,this can happen when you move h/drive around.

Monitors don't have a/c adapters...they just plug into the wall....they use a standard grounded pc plug. you can see for yourself by unplugging your pc and using that plug into your monitor. it should fit. good luck

Your HP notebook PC probably has a VGA (aka HD-15) connector. Check page 16 of this PDF to make sure - connector #2 is the VGA connector.

Your Compaq monitor also has a VGA HD-15 connector, so it should plug directly into your laptop's port after unplugging it from the other PC.

You will still need to plug the Compaq monitor's power cable into a wall outlet for power.

If you are going to share this monitor between your notebook and the other PC, you may want to consider purchasing a Keyboard-Video-Mouse switch (known as a "KVM switch") - there are many different models - you will need one with VGA, and whether you need USB or PS/2 keyboard/mouse connections depends on what your other PC's keyboard and mouse are.

Does the cord plug directly from the wall into the monitor, or is there a power "brick" adapter between?

If there's a "brick" listen to see if the hissing is coming from the monitor itself or the brick. If the hissing is coming from the brick you may just need a new power adapter.

If there's no brick or the hissing is coming from the monitor, the monitor probably needs repair. With the price of LCD monitors these days compared to the price of labor, you're probably better off getting a new LCD monitor. Just make sure you take your old one to a proper E-Waste facility so it doesn't pollute the environment.