Here is a simple diagram that will help you to understand how a notebook display assembly works and how an image appears on the screen. I’m not an artist and I tried my best drawing this diagram, so if you cannot see a laptop in this picture, don’t be mad.
A generic display assembly includes a very few parts and knowing them will help you to understand witch part can cause a problem if you laptop video not working properly.
Video cable. A video signal from the motherboard goes to the LCD screen through the video cable. The video cable connects to the motherboard (or video card) through the connector 1. The video cable connects to the LCD screen through the connector 2. The video cable (in most cases) is also responsible for supplying a necessary voltage for the FL inverter board. The video cable connects to the FL inverter board at the point 3.
FL inverter board. This board is responsible for converting low voltage DC power (point 3) to high voltage AC (point 4), necessary to light up the backlight bulb. If the FL inverter board is bad, the LCD screen (backlight bulb) will not light up when you turn on the laptop, but you still should be able to see a very dim image on the screen.
CCFL (backlight bulb). When the backlight bulb lights up, you can see an images on the LCD screen. In most cases the backlight bulb is a part of the LCD screen and if it’s bad, the entire screen has to be replaced. By the way, some specialized repair shops can replace the backlight bulb itself.
Lid close switch. The lid close switch is a small button that locates close to the display hinges. On some newer models there is no button, because the switch is magnetic. You can set up your laptop to go to a hibernation mode or to a standby mode when the LCD is closed. It’s done through power management software. These modes are triggered when the display is closed and the lid close switch is pressed down. If the LCD screen on your laptop will not light up when you open the display assembly, check the lid close switch is stuck inside (it might happen because the switch is dirty).