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 19th, 2008 at 3:51 pm
Is there a way (other than trial and error) to know if its a bad inverter board or LCD assembly (with backlight)?
Could be either and there’s a large difference in costs relative to each.
September 15th, 2008 at 9:45 pm
mur,
There is no way I can tell you witch one is causing the problem without testing your laptop with another working backlight or inverter. Could be one or the other.
From my experience, inverters fail more often than backlight lamps.
September 15th, 2008 at 9:00 pm
Very good topic. Thanks.
I’ve a Sony Via (VGN -CR190) laptop. When I power on the laptop, I can see a very dim image when showing the screen to light. When I connect the laptop to external monitor, I can see clear image in the external monitor. Is it problem with Invertor or bbacklight or LCD screen.
September 9th, 2008 at 5:19 pm
Buting,
Test your laptop with the old LCD screen and inverter again. If you still have backlight with original parts, apparently your new parts are not good.
Make sure the new LCD and inverter are compatible with your laptop.
Test your new screen with the old inverter.
September 9th, 2008 at 5:16 pm
Cristina,
Make sure all display parts are properly connected to each other. Try swapping parts. For example, test the old screen with the new inverter and cable, test the new screen with old inverter and cable, etc… Try different combinations.
I don’t know. It’s possible that your new screen is defective OR your new inverter board is bad. I cannot tell which one is causing the problem without testing your laptop with known good test parts.
September 8th, 2008 at 8:16 pm
got a c2220 lifebook with a broken lcd but the backlit is still working before I replace the lcd. replace lcd and inverter but now there is no display or image or backlit. please help. ordered a video cable already
September 5th, 2008 at 6:32 am
Hello,
I have a Hp Pavillion zv6000. One month ago the screen start show some horizontal stripes, but moving a bit the screen all goes away.Sometimes I got my screen froze and finally one day went totally black. But most like everyone, when in lighted place I could see the images on the screen. So I connected my laptop to a external device to be sure.Everything works fine. So I decided replace the LCD screen thinking was the backlight bulb.
Turns out that the screen still black even with the new screen. So following the possibilities I changed the inverter and nothing changed. In my last attempted I replace the LCD cable even thought this want’s the problem since I could see the images when have my laptop in a light place.
Do you think the backlight bulb in the new screen come death already?
There’s any other thing I can try before I give up and take to a repair?
I also checked the closed swich and was how is supposed to be.
Thank you
August 31st, 2008 at 3:59 pm
ya frendz… the same vertical straight line has been also appeared on my Compaq Presario V3137TU notebook today. it really hurts….
the waranty period has also been expired, i’m really shocked.
even after knowing the facts by you people that i’ll be coming continuously…
convey this message to compaq “i’ll die”…
August 31st, 2008 at 8:45 am
I do fix a notebook, but this time a have a problem with the C-mos, How do i clear the C-mos to remove the passord?
I love all your fine comments. thanks
August 28th, 2008 at 6:37 am
with in one week, after I bought dell inspiron 1420 laptop got some problem with display like halk of display pure black, remaining half normal. this is happening only at password entering page (after windows logo loading) I complained to dell, they changed MB, and Display still pbm existing. vedio driver also updated. but no improvement. what i can do further? please give me ideas.