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 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.
November 30th, 2007 at 10:12 pm
Sam,
Does it look like one of the lines on the example 2 in this post? If it does, you have a defective LCD screen.
You should return your laptop and exchange it for a new one if you can.
November 30th, 2007 at 10:09 pm
Stacy,
I assume this high pitched squeal is coming from the inverter board, I don’t know what else can make this sound inside the laptop display panel.
In order to narrow down the problem and make sure this sound is coming from the display panel, it’s necessary to open up the laptop, unplug the inverter/video cable from the motherboard/video card and test run the laptop for a while with an external monitor. If the laptop is quite while running with the external screen, most likely there is a problem inside the display panel.
Here’s another way but it will work only if you have the lid close switch – small button located somewhere close to the hinges (not a magnetic one). First you’ll have to change setting to “Do nothing when I close the display” in the power management utility, so the laptop doesn’t go into hibernation/standby mode when you press on the lid close switch. Then wait until the laptop start making this high pitch squeal and press on the lid close switch. The screen light will turn off. If the squeal goes off when you press on the lid close switch, most likely this problem is related to the screen inverter. You’ll have to open up the screen and replace the inverter board.
I doubt that this noise is related to the sound card driver.
November 30th, 2007 at 11:50 am
i just bought toshiba laptop and after a week, i have notice an image on the screen like a straight blue/white line from the top to bottom…can any body advise what it is and can it be solve in a simple way..or i should return my laptop? please share your insight. Thanks
November 30th, 2007 at 12:39 am
Seems like you were right cj, well done. I stripped the machine again this morning untill all that was in it was the board, VGA and the CPU, still nothing – dead as a door-nail.
I then pulled the VGA from it and booted it again, and to my surprise it beeped (now we know, Acers have beep codes), 1 long – 2 short, which obviously points towards the VGA(which was out), so I knew the VGA was fine.
My next step was something I really didnt want to do, but needs must, the problem I had was that I didnt have good spares to test on the machine, so I ripped open my own laptop ( Atec Vegus 198) which has got a Sempron 2800 inside (with the same socket 754) I dropped my Sempron in place of the Athlon and nothing, still dead.
My next move was to stick the Athlon chip into my Atec machine, boots fine had a play, everything was fine – although it did identify itself through the system panel as a Sempron 3000 even though it is labelled as an Athlon 3000 !!!.
So all thats left is the motherboard, a replacement part which is probably harder for me to come across in this part of the world. Again I sent email round all the local Acer service centers, still waiting for a reply. I did find a replacement from http://www.notebooksolutions.ca priced at 250 USD ( but I gotta send the old MB first before they send it.
Thanks for your help cj, much appreciated mate.
Ray
November 29th, 2007 at 3:16 am
cheers for the reply cj,
some interesting points you bring up there, I just wish I had checked this forum earlier, I am getting ready to head home now, I will try the ‘barebone’ approach in the morning and let you know how I get on.
As far as the ‘beeps’ are concerned, yeah, its a standard feature on desktop PC’s, I have tried numerous times to contact Acer requesting information on this with regards to this machine but they are totally useless.
In the event that it was the VGA or the CPU I have been trying to source these items (as my customer needs his machine back pronto), but it is very nearly impossible to get these items here (I am in Thailand), the Thai market is a very closed ecosystem with limited stocks of anything older than 2 years. Yes, if I went out searching 2nd hand PC shops I would probably find what I need but to get them from any form of supplier is impossible. We live on an island very far from Bangkok, so there is nowhere for me to look that is local.
Just some advice for anyone in the same situation – dont buy from Acer (or DELL, their support sucks too).
cheers again cj.
November 28th, 2007 at 10:06 am
Hello!
I have a Sony VGN-FE590P in fairly new condition. I use it 12-15 hours a day. By noon the high pitched squeal that is coming from the screen makes me want to shoot myself. At first touching the screen subdues the sound but as the day wears on the squeal is louder and more persistant. It need a little tap or flick to the back or sides of the screen to subside. If I use the display properties to change the settings the noise stops when the screen goes blank during the change which tells me this is definitely the screen. Sony is no help they just tell me to reinstall my sound card driver. The laptop otherwise has no other problems. Is this the norm for this model or can I fix it somehow? I have worked extensively repairing desktop computers but I am afraid of the shiny fancy laptop.
Thanks
Stacy
November 27th, 2007 at 11:03 pm
Ray,
First of all, you checked the AC adapter, right?
Try reseating the VGA board and test the laptop again. Just disconnect it from the motherboard and connect back in. Have you tried it yet?
I agree. If known good memory stick didn’t help, most likely it’s not memory problem.
Are you sure that your ACER should beep if it’s “missing” the video card or memory? I fixed many different laptops but only very few of them beep if you forget to install memory or the video card is bad. So, I’m not sure about Acers.
Yes, it’s possible but from my experience CPU failures are not very common. I’ve been fixing laptops for over three years and so far I’ve seen very few failed processors, maybe five or six, not more. For these three years I’ve replaced many video cards, thousands motherboards and only few CPUs. In your case, if I would have to guess, CPU would be the last component to replace on my list.
Ad I mentioned before I don’t have any experience with Acer laptops, but I think I would try replacing the VGA board first.
Here’s something you can try. Try to assemble a barebone laptop system outside the laptop case, somewhere on your bench. Use only four components: motherboard, CPU with heatsink, VGA board and known good memory. Connect an external monitor and see if you can get video. Carefully press on the video card, so it’s making a good contact with the motherboard and see if it makes any difference.
If the motherboard gets power and you can see some LED activity when you turn it on, but there is nothing on both internal and external screen, try replacing the VGA board.
This is just a guess that I’m making over the Internet without even looking on the laptop.
November 26th, 2007 at 11:43 pm
Made a fair bit of progress since last night, had the machine stripped down to get all the part numbers from the board, VGA and CPU. After more tests I have since came to the conclusion that the CPU is dead, you see all through this job there has been no beeps from the machine at all during startup, or anmy other time.
So I pulled the RAM out from the machine, again nothing, surely it should be beeping away like mad. I swapped in RAM last night from another Acer laptop and still nothing so I discounted the RAM then.
I still thought it was possibly the VGA, but again the lack of any beeps during POST made me more inclined to discount the VGA as the problem.
The problem I have is that I have limited spares to swap in, it means purchasing the item just to test it.
I have contacted 3 Acer support sites(Holland, Thailand, England) over this and there is still no reply, all I wanted from them was the availability of the VGA board as I could not find it anywhere. I would not recommend anyone to contact Acer, ‘laptopguy’ is much more attentive.
Would you agree with this assessment that it is most probably the CPU?
Thanks for all your help.