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.
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January 6th, 2007 at 7:10 pm
Hi, Laptop Repair Guy: I have a Toshiba model 1955 laptop. In trying to correct an overheating problem, I disassembled most of the computer before cleaning the air blower chamber, because I had trouble with the cover screws, and thought I could take the whole bottom pan off. Had I read your site first, I would not have made the mistake.
After I assembled the computer, the overheating problem is solved, but the screen does not light up, even though it was working fine before the repair. I presume there is a faulty connection somewhere that sends power to the screen even though I the only cable I disconnected was the one to the hard drive, but the system seems to be powering up fine. Can you give me some idea of where to look for the problem, or how to test to verify if the connections to the screen are feeding signal and power to the screen?..
Thanks for your help. Tom Erickson..
January 3rd, 2007 at 9:28 pm
Hi,
Your instructions are great — thanks!
I am getting a faint screen on my satellite A45-S150. It happened after I dropped my laptop on the floor.
I have followed some of your instructions, and so far have been successfully able to dismantle the LCD. However, I have no clue what I should do next. Should I
1.) check whether the lid close switch is “closed”? If so, where can I find such a switch on Toshiba Satellite A45-S150? Is it magnetic?
2.) check the FL invertor board? If so, how can I check if it is working fine or not?
As usual, your feedback will be invaluable.
January 3rd, 2007 at 5:49 am
I have an old compaq armada 7800. Recently the screen goes all discoloured(reminds me of a mood ring) and the screen goes white. If i squeeze the sides sometimes the image will come back or sometimes freeze. Should I take it apart ? Is there a way to tighten the frame because it seems like the squeezing of it sometimes helps
January 2nd, 2007 at 10:39 pm
I have a DELL Inspiron 8200. At first, monitor would start to display distorted lines until they consumed the screen. Initially, a firm yet loving thud would clear it up. Pressing around the keyboard varied the distortion patterns. Now, soon after startup, screen quickly distorts then goes blank (not dim, completely blank). I hooked up an external monitor and that works fine. I took it to a friend and naturally it worked fine for hours…got it home and problem back. I’d really like to fix it if I can.
January 1st, 2007 at 12:21 pm
Your instructions are great!
Based on what I’ve ready I may have a stuck lid close switch. The laptop is a fairly new Gateway 7326 which I’m guessing has a magnetic switch. I just can’t find it! Any ideas on where I should look or how to find it?
December 29th, 2006 at 7:15 am
I have been checking a Presario X1000 notebook. It was working, hang up, mu client restarted it and it never came on again. No video, no sound. The first thing I noticed was that the cpu fan sopped spinning 3 seconds after I turned the notebook on. It has the video card on another board, I pushed the card by the superior part, near wher the screen connector is, and the notebook started normally, I reainstalled Windows XP and I installed Max OS X for intel on it. But if you merely hit the notebook or put it too strong on the table, the same problem again, I was as at the beginning. I have cleaned the video card contacts with contact cleaner and nothing. The video card has two sockets to the right side of it, I cleaned the connector sockets and nothing. Any idea?
December 25th, 2006 at 8:48 pm
Shawn Moss,
If you feel comfortable taking the laptop apart, you can fix it yourself. Here’s a link to IBM ThinkPad A21m hardware maintenance manual, this manual has step by step disassembly instructions. You can find a new video cable relatively cheap – $15-20 here.
December 25th, 2006 at 8:30 pm
Asteros,
It depends. Connect an external monitor and set the laptop to output video on both screens – laptop LCD and external monitor. Wait until the video fails. If the vertical line appears only on the laptop LCD but not on the external monitor, then most likely you have a bad LCD screen and have to replace it. If the line appears on both screens, then you have a bad video card, in this model it’s integrated into the system board. You’ll have to replace the system board.
I think you have a bad screen.
December 25th, 2006 at 12:20 am
Ok now heres my situation,I have a old 2001 Ibm thinkpad a21m laptop…..the video cable which connects the lcd screen to the laptop motherboard was damaged,in damage i mean it was puctured.How can I fix it “Myself”? and if its not possible for me to fix it.How much would you think it would run me for? thankyou
December 24th, 2006 at 10:58 pm
I have a Toshiba Satellite P35-S611 laptop, which is 1.5 years old. Recently, I noticed a vertical purple line that comes up every so often. Does it mean that my LCD monitor is gonna die? What needs to be replaced?
Thanks for a prompt answer