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.
January 17th, 2007 at 8:01 pm
Jim,
Check the power management settings, you’ll find it in control panel. May be the brightness is set to minimum when the laptop runs on AC power? I believe on some Dell laptops you can also adjust brightness in BIOS. Enter the BIOS setup and check if there are any settings for it.
Finally, try upgrading/reflashing the BIOS.
January 17th, 2007 at 7:31 am
pls send me details on how to troubleshoot when the screen is flickering.
thank you
January 14th, 2007 at 4:03 pm
Daniel Vizante,
January 14th, 2007 at 11:01 am
Jyoti,
First of all, I would open up the display assembly and check if both connectors on the inverter board. Make sure the connectors are seated properly, reseat them just in case. If reseating cables will not help, most likely you have a problem with the CCFL tube (backlight bulb). Probably it’s been damaged.
By the way, may be the screen lights up for a moment when you turn on the laptop or it stays black right from the beginning?
January 14th, 2007 at 10:02 am
Thank you very much cj2600…I’ll give it a try.
January 13th, 2007 at 10:40 pm
Scott Smith,
You have an intermittent problem with video and very likely it happens because of a loose video harness. Check if both ends of the video harness are seated properly. Check the connection on the motherboard/video graphics card first because it’s easier to access and after that check the connection on the LCD screen. Here are instructions for removing and replacing parts on Dell Inspiron 8200.
January 13th, 2007 at 9:19 am
I recently replaced the lcd on my dell 9300 which had the typical vertical lines and eventually half the screen was blocked out. i bought a new replacement off ebay and it’s great other this one problem. When it runs on the battery the screen is very bright and seems to be normal but when it runs on ac it goes dim. I can still read everything but has to be in an almost dark room. What do you think is causing this unusual problem. by the way with the old screen this problem was just the opposite. thanks.
January 10th, 2007 at 4:57 am
I just followed your advice and replaced the FL inverter board which fixed my Acer Aspire 1804wsmi which had a dark screen with graphics which were just visible. Thanks Laptop Repair Guy !
January 7th, 2007 at 5:15 am
I have an Amilo Fujitsu Siemens with no backlight (I can see the imagine but very dim). It is possible to change only the converter ? Or I have to replace the hole LCD ? I have no high voltage (1500 V)
January 6th, 2007 at 10:08 pm
Hi, Laptop Repair guy: Here is the answer to my own question regarding my Toshiba laptop model 1955, that after disassembling, the system seemed to power up fine, except that the screen remained black, and appeared not to be getting power. I read your instructions for checking connections to the strip wire between mother board and screen, and found that there is a removable snap-on plastic cover over the screen hinge section, under which the wires that come from the motherboard are plugged into a socket. Apparently in manipulating the screen, the plug came partially out of the socket, causing a false contact to the screen. I pushed the plug down into the socket, and as soon as I powered up, my screen started to function properly. Thanks for informative site, that helped me solve the repair problems.