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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September 7th, 2006 at 2:33 pm
Charz,
). Some sellers on eBay offer a new inverter for $9.50!!!! ($3.49 inverter and $6 shipping). Under $10 for a new inverter that’s the best price I’ve ever seen. It might last you forever or just for a few days, nobody knows.
If a new fl inverter fixes your backlight problem, you might consider yourself very lucky. Because it also could be a screen problem (you don’t want to know how much a new screen is
September 7th, 2006 at 2:19 pm
Well it definately isn’t the lid button anyway. So must be what you said. How long roughly would it last if I replaced it? I can’t afford a new laptop, so this one has to go til the death
(Plus it’s 2nd hand, 2nd hand! Person I bought it off is lucky(?) to have a uni grant so bought one for like £800 :-0 )
September 5th, 2006 at 2:21 pm
A dim laptop screen might be caused by a failed FL inverter or a failed backlight bulb on the screen. I would say that most likely the FL inverter is bad and replacing it is not as expensive as replacing the screen. Check out this post that covers troubleshooting laptop video problems in more details.
A new FL inverter will cost you probable somewhere around $20 (from eBay). You’ll find a disassembly guide for IBM ThinkPad here.
September 5th, 2006 at 2:14 pm
My ibm thinkpad t21 screen is very dim, can just see the screen, but it’s bad. Just seen your bit about the button near the hinge which hibenates it. So I’m going to go and have a look.
Someone said to me that it might be the backlight. Is this expensive to repair if it is?
thanks
August 18th, 2006 at 8:32 am
Victor,
I think you’ll have to replace the reserve battery. Here’s a quote from Dell Latitude C810 service manual:
Follow Dell Latitude C810 service manual to replace the battery.
August 18th, 2006 at 8:16 am
The laptop also says “invalid time and date” and asks you to fix it in bios every time i unplug the laptop. Is there a cmos battery to replace in the C810 or is the regular battery needs to be replaced?
August 17th, 2006 at 5:28 pm
Victor,
most likely the LCD screen is bad.
August 17th, 2006 at 5:23 pm
I have a Dell Lattitude C810, the LCD has a vertical red line two inches from the left and a vertical blue line one inch from the right.
If I move the hinges a third and forth red line appear on the screen does this mean the LCD is bad or the cable?
I hooked up a CRT monitor and no lines appeared.
Email let me know.
July 26th, 2006 at 9:35 pm
Ngbede,
First of all, try to reload the video driver.
You can try to fix the lines on the screen by reseating the video cable on the system board (or video card). It’s connector #1 on the diagram above. I think you might have a bad video cable problem because the lines are changing the size. When you have vertical lines because of a bad LCD screen, they usually stay the same size all the time. Have you tried to connect an external monitor? Does it work fine?
July 26th, 2006 at 7:33 pm
Liza,
Before you replace parts, start the laptop with an external monitor attached. If you get a video output on the external monitor, then most likely the system board is good and you have a problem somewhere inside the display assembly. If not, then you might have a problem with the system board.
I think it could be a bad video cable. I would try to replace it first. You have a good chance to fix the problem and the video cable is not as expensive as a new screen. If it doesn’t help, then you might have a problem with the screen (very expensive repair).