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.
June 20th, 2008 at 5:36 pm
dear sir
i got acer laptop its working down but not display i cheak the external moniter but also not working.i cheang the cpu ram internal bettry also same problem .
June 8th, 2008 at 6:35 am
I have Dell Inspiron 1420 laptop with me. When ever it tries to connect to internet the screen goes off and comes back.Even while starting the screen goes off and come back to show the desktop icon. please help
May 31st, 2008 at 8:06 pm
Kelly Vlasis,
You cannot see any image at all, even a very dim one? Try looking under the bright light, still nothing?
When you turn on the laptop, does the LCD screen changes color from completely black to gray, or it stays the same (black) all the time even after the laptop is up and running?
May 29th, 2008 at 8:07 am
Hello, I have a Dell Inspiron 8200 laptop. I cannot see any display on the internal LCD but have been using an external monitor and can see everything fine. Has the backlight gone south on me? What are your suggestions? Any help is appreciated.
May 22nd, 2008 at 9:17 am
Hello.
My laptop is not power on.What is probulam?
May 18th, 2008 at 8:30 pm
[...] Is it possible to test laptop screen inverters with a regular multimeter? I was asking myself exactly the same question many times before until I found this article published by Morris Rosenthal. [...]
May 14th, 2008 at 10:20 pm
David,
Let me know your laptop model number, it’s on the same sticker with the serial number and I’ll look up the LCD part number for you.
May 14th, 2008 at 9:13 pm
Hello..
My screen is cracked and I am looking for a replacement. I’ve been looking for some LCD screens, but how do I know if the’ye compatible with mine?
(Toshiba Satellite 17” P205-S6237)
May 2nd, 2008 at 3:35 pm
Steven,
Check the BIOS version running on your laptop. Toshiba issued many different BIOS updates for this model and some of them address the video problems. Try updating the BIOS, it might help.
WARNING! Make sure to install correct BIOS. Toshiba offers BIOS 2.XX series for Windows XP and 5.XX series for Vista.
May 2nd, 2008 at 3:25 pm
margaret,
There is no simple answer for your question. I assume that when you plug the power adapter you can see that power LED lights up but when you press on the power button nothing happens. Does it sound like your failure?
You have a new power adapter, so it’s good and the laptop gets power. In order to start any laptop with video you need three main components: motherboard, CPU and memory to be in good working condition. I would test the memory first. Try reseating the memory module. If you have to modules remove them one by one and test the laptop with each module separately. If the problem is not related to the memory, then you may have more serious problem.
That’s all I can suggest without looking at the laptop.