When turn pc monitor no signal

Make sure you are connecting the monitor signal lead to the correct signal output on the rear of the machine. Some desktops have extra video out connectors when they have a graphics card fitted. If yours has a graphics card the display connector will be away from the back USB ,audio and keyboard ports and near to some silver pop out panels near the bottom of the tower.

The monitor is not getting a video signal from the PC. Try a different monitor. Or add a new video card to the PC.

No signal is not a problem with the monitoe unless the cabe is disconnected from either the PC or the monitor ends.

If the cables is securely attached at both ends it indicates the PC is not sending a video signal to the monitor.
Could be the PC hasn't booted up propperly.
Turn the PC off , wait 2 minutes and turn it back on.
Observe any lights on the front of the PC , especially disk activity light.. it should flicker .. alot.
If not then you have a PC issue not a monitor issue

1. change the VGA cable and test.
2. Plug to another PC or notebook and test.
if still no signal, it might be the display board inside the LCD is faulty.
You need to get a certified technician to fix it.
If cost is higher than 1/3 of a new 18.5" new :LCD monitor; I think you need to think of purchasing
a new LCD already. As new LCD will cover you with 3 years warranty.
take care.

It means it does not receive the video signal from the PC video card, check all pins on the video cable, also try this monitor with other PC.

http://s807.photobucket.com/home/budm/allalbums
http://en.wikipedia.org/wiki/Capacitor_plague
http://www.badcaps.net

If it does the same with other PC then you need to open it up and first thing to look for are bad caps in the power supply, see example of failed monitors due to bad caps, transistors, transformers, lamps: http://s807.photobucket.com/home/budm/allalbums
Post back what you see inside, and always replace with good quality caps such as PANASONIC FM or FC series from DIGIKEY.

1/ first change motherbord on your desktop.if it is work (your old bord is damage ).then keep graphic card/ vj card on old mother bord slaut. if not work . it is seriously problem.mainly in pinless bord we can"t repair it. change or took it on export

This Problem is Acer(s) Monitors. Though it is a nuisance one fix That has work for many is the Unplugging after it goes back to Good (viewable) screen.
I have hooked mine up to an inexpensive Power strip to make it easier for me and just turn off at time indicated above and Viola Simple is as Simple does :)

The interface between the monitor and the cable might need replacement. Please check it.

The No Signal thing is your monitor saying it doesn't have anything from the PC to display; the PC has nothing to do with that.  Try refitting the card to the PC to make sure it's in there right, and if your PC boots then you should see something (especially if your cables are all plugged in right and your monitor is paying attention to the interface the PC is on, not some other source it could be fed (e.g. SVHS, composite, DVI-D...)