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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December 23rd, 2007 at 1:14 pm
ama inder singh,
You’ll have to test your laptop with an external monitor and find out if you have the same video defect on the external video. From your description I can assume that you might have a problem with the graphics card or video memory.
If both laptop LCD screen and external monitor display same dots and lines, this problem is not related to the laptop LCD. Most likely there is something wrong with the video card or video memory. If the laptop has shared video memory, when a part of the main memory is used for the video purposes, it’s possible that the main memory is going bad. Just in case run memory diagnostics test and see if it fails. You can use Memtest86+ utility.
If video is bad only on the laptop LCD screen but the external monitor works fine, it’s likely that you have a problem with the LCD screen. I would also try reseating the video cable on the motherboard and on the LCD screen, just to make sure it’s not a connection related issue. If the video cable is not making a good contact with the screen or motherboard, you can get all kinds of video issues.
December 23rd, 2007 at 1:00 pm
April Meunier,
I don’t think this is a virus, to me it sounds like a hardware related problem. This laptop is still under warranty, right? Just send it back to Dell for repair.
December 23rd, 2007 at 12:19 pm
heyaa laptop guy .. i have a fujitsu seimens laptop and i was using it all of a sudden a blue page displayed which said errorr……….. then i restarted the computer and discoverd that it had crashed so i switched it off again and left ih however i am now trying to switch it on and deres no display whatso ever on the screen i can hear the drives and everyfing could u please help me .. urgentlyyyyyy
December 23rd, 2007 at 4:25 am
I have this HP Pavillion dv2002tu model,just over an year old anf suddenly yesterday the whole screen has this pink and green dots which seems to be in constant motion at their own place.When a black screen of startup or the cmd prompt is there I see loads of small green dots which are flickering on their fixed postion all over the screen.Also when there is blue screem,evryhtng seems ok as no dots are visible and all white areas have small pink dots like th border of this message window is full of pink dots.Also during startup,I see three vertical green line,one in the center,another on extreme left and 1 cm from the right.
Kindly help….what is the reason..i have restarted it,reinstalled video drivers and formatted HDD..but nthng changes…Do i have to replace the LCD screen…hw much will it cost for 14.1′ widescreen to be replaced.I am from chandigarh,India
Looking forward for a reply…
December 17th, 2007 at 4:29 pm
I have just bought a Dell Vostro 1000 a month ago. I am having problems with the screen turning white and at different times it has blue and white horizontal stripes. It happens about twice a day and I have to restart the computer when it happens. Dell says it is a virus but I don’t have any. They have not been much help.Can you help me please.
Thanks, April
December 7th, 2007 at 4:06 pm
I accidently dropped by 3 month old HP laptop and now the display is gone. I have a old DELL Latitude Laptop, is there anyway I can connect the HP to the DELL display?
Thanks,
Anna
December 7th, 2007 at 6:45 am
Hi,
I have sony vgn-s260 laptop,i have changed motherboard recently,because computer wont’t boot up,now i have new motherboard(second hand) and laptop boot up but no graphic at all.black screen,i can hear that laptop is working hard drive etc.,but nothing on screen,i have even plug external monitor to vga-out ,still nothing no signal,do you think it is a bed graphic chipset on motherboard?thanks
December 5th, 2007 at 7:54 pm
Thanks cj2600. I will try it this weekend. Will let you know if that works. I am also guessing that the backlight lamp from the old screen can be used with the new screen. Thanks again.
December 4th, 2007 at 12:15 am
neela,
Could be connection related issue.
Do you still have the old cracked screen? Even though the screen is cracked, probably the backlight inside the screen is still working and you can use it for testing the laptop.
Connect the old cracked screen back to the laptop and turn it on. If the backlight on the old screen works all the time and will not turn off, most likely there is nothing wrong with the inverter board. This way you can test the inverter board.
Now, when we eliminated the inverter board, there could be two other problems. Either the backlight lamp inside the new screen is not good or the new screen is not making a good connection with the inverter. Unfortunately you cannot find it out until you make a good connection between the new screen and inverter board.
If you have nothing to loose, you can cut off the old connector from the old cracked screen and solder it to the new screen. If after that the new screen still goes dim after a while, apparently it has a faulty backlight lamp inside.
December 1st, 2007 at 8:37 pm
Hello, I have an old Toshiba Satellite a45-s150. When my lcd cracked, I replaced it with something from ebay. The connector at the end of the two wires that go to the fpl inverter did not fit into the original fpl inverter. So I took the connector off, and jammed the two wires into the connector that came with the original lcd screen — not soldered or anything, but just pushed them in real hard. This worked ok for a few days. Then the screen started to go blank (with a very faint image). If I opened the bezel, push the wires back in and closed the bezel, it make work a few minutes, but go blank again. Now the bezel is completely off, and even if I pushed the wires hard into the connector, the screen is not coming on. At one point I thougt it may be a lid close switch, but I couldn’t find any such switch on the machine. So what are the odds? Is it the fpl board itself, or the lcd screen itself, or just teh connector? or the switch that I haven’t found yet? How can I more reliably connect the connector to the wire? Is there a place I can buy a new connector, and crimp the wires in? Separately, what is an inexpensive place to buy a broken hinge? A $100 on ebay for a hinege felt pricey!!. Thanks a lot for your help.