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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November 26th, 2007 at 1:21 am
Ray,
Check the memory first. Try reseating the memory module because there could be some kind of connection issue. Try replacing it with a known good module and test again.
November 26th, 2007 at 1:18 am
Martin Ruge,
I believe this is a problem with the LCD screen itself, not the video cable.
November 26th, 2007 at 1:02 am
Looking for ideas as to identifying faulty hardware. I have a laptop that the screen suddenly went blank whilst in use. There are no ‘beeps’ during startup, the screen is totally blank, not even a faint image, and when plugged into an external monitor there is nothing. My instinct tells me its the video card but the lack of system beeps during POST is making me doubt that. The lack of a faint image tells me its not the inverter board either.
Any ideas? I dont want to order in a new VGA if the problem lies elsewhere. Any ideas on testing to identify where the fault is?
The machine is an Acer Aspire 1522 WMLi. I am even having trouble identifying the VGA card inside it to price a replacement – currently stripping it down to view any parts numbers inside the chassis.
Any help of advice would be most appreciated.
November 17th, 2007 at 3:35 am
Dear all,
I`ve some trouble with the display of my notebook . The notebook is a HP Pavilion zv 5000. One day I closed the lid of the notebook, after I opened it I had a vertikal bar on my screen. Within the bar, the text or whatever is displayed correctly, but it is darker than text on the remaining screen. Isit possible that only the video cable is broken?
Martrin
November 16th, 2007 at 3:42 pm
Can someone help me with a sony vaio fx 220 laptop that has no video at all? I tried an external monitor and nothing. Any help will be appreciated.. thanks
November 14th, 2007 at 1:25 pm
My laptop will only work if I leave it on the charger and it always says it is charging and it is at 0%, and I will leave it on the charger for a day but it still says 0%. What should I do?
October 29th, 2007 at 11:33 am
Hi
I’m in the process of helping a friend to change his toshiba satellite m70-340 smashed screen. The original screen is a LTN154x3, and the replacement screen is a LP154w01.
The new screen works but is about half it brightness when the brightness sitting is set to the maximum on the laptop. I know the new screen is not faulty as I tested it on another laptop and worked fine. I know that the inverter on my friend is not faulty too, as when used with the smatshed it works fine.
So how can I get the new screen to light properly?
N.B. With the new screen in the keys that adjust the brightness work in revers; the one suppose to increase the brightness decreases it, and the ine suppose to decrese it increases it.
October 21st, 2007 at 12:01 pm
Kevin,
Can you see a very faint image on the screen? Does the backlight flash when you tapping on the lid close switch? Does the screen change color (maybe just a little bit) when you turn on the laptop?
October 18th, 2007 at 11:00 pm
Hi, I have a 5-year-old Dell Inspiron 600m that recently the LCD screen won’t light up. It powers on and powers off fine but the screen stays black right from the beginning. External monitor works OK. I have tried reseating the cable connector but it did not solve the problem. This problem had happened three or four times before and usually after powering it on and off several times, the screen would light up. I noticed that the problem only happened if I turn off the laptop. I used to leave my laptop on my desk all the time and always put it into stand-by mode and I never experienced the problem. Recently, since I travel with my laptop everyday, the problem happened more often and now it’s been almost three weeks the screen did not work. I would like to know if the problem is related to inverter or backlight bulb?
October 13th, 2007 at 9:09 pm
somveer,
This problem is not related to the backlight or inverter. I think this problem is related to the video card.
Make sure to test your laptop with an external monitor. Can you see the same vertical dotted lines on the external screen? If yes, this problem is related to the video card.
If your laptop has shared video (part of the main memory is used for video purposes), run the memory test. If the memory module fails the test, replace it and see if it fixes the problem.