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.
Looking for a new screen, video cable or inverter board? Find it here.
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).
Related articles:
Fixing notebook video problems.
If you find this article useful, please consider making a donation to the author. Thank you!
September 23rd, 2010 at 3:03 am
dear sir i have laptop hp povilion xt 118 problam is laptop screen is white light but no video
September 16th, 2010 at 1:43 am
Update:
It was the switch and I have played with it with the same magnet from the lid. I can get the screen to stay on only under one condition: as long as the screen is opened in an acute angle, any further and the back-light shuts off.
September 16th, 2010 at 1:02 am
I have an Acer Aspire 4720z laptop. I have had a few major hardware problems with it before but it was nothing I couldn’t handle. Internal power plug broken? Solder the cable directly to the power card… But this one has me baffled.
I just reattached the power cord the other day for what seams to be the 15th time when the screen looked like it wouldn’t cut on. I looked closer and noticed that it was indeed on but not lit up. Took it apart and saw that I didn’t rout the monitor cable right. Rerouted it and it worked just fine.
I had to take it apart again soon after because I forgot to reconnect the ribbon to the audio jacks and volume control wheel. When I started it back up it gave me the same problem I had before. I knew then what it was not; it’s not a power problem and it’s not from a pinched cable so it must either be the LCD back-light has finally kicked the bucket or it’s the inverter card. So I just plugged in a monitor and went on my way.
After an all day gaming session today I noticed that when I opened the lid to turn off the computer, the screen was lighting up… at least until it reaches about 90 degrees and then it shuts off. Is this a problem with the magnetic lid close switch and if it is where the devil would it be located? On the motherboard?
I looked and all I can see that would be anywhere near the magnet that could be the switch is a little black component that is 1mm x .5mm that has 3 solder connections. Two of which are on one side close to either edge and then the 3rd is on the opposite side right in the middle.
Is there a way to repair the switch without having to have to replace the motherboard or the switch. I am on a budget and that is not something that I would be able to afford.
September 13th, 2010 at 9:26 am
hi i m having hcl laptop. i am having problems with its display. earlier i got replaced the fl invertor board. but now the problem is that there are black spots on my display that increase and decreases auto matically and also a white horizontal white 1 pixel line shows. please help me to get over this problem. it would be a grat favour if you mail me the solution. bye
September 7th, 2010 at 7:54 am
Hannah,
You said this is bright rectangular area. Is it like a white bar running from top to bottom?
If yes, this is LCD screen failure.
September 3rd, 2010 at 10:37 pm
Hi! I am having a problem with my HP DV7-3085dx Notebook, because why all of a sudden a bright rectangular area appeared on laptop screen. I would like to show you pictures or send them to you via e-mail of what I am describing, that is if anyone is interested. Please help me in diagnosing this technical problem.
July 11th, 2010 at 7:25 am
@adnan Press Fn+F8
May 18th, 2010 at 12:00 am
hi, i am working on laptops repairing. i have problem in sony vio (VGN-CS 230J)laptop. when i connect to charger in running condition, after hrs laptop power off or tripped. please tell me suiable solution.
i will thankfull to you for this kindness.by
March 7th, 2010 at 9:06 pm
Hi I’ve got a Compaq V2000 working fine till I got back yesterday after leaving it on downloading stuff. I now have bottom 2/3 of the screen having horizontal bands across that looks like double images. Tried to reseat the video connectors don’t work, hooked to an external monitor and it works fine. Could it be the lcd that need to be replaced or should I try a new cable?
Thanks
February 24th, 2010 at 1:25 am
thank you sir, I learn more from you.