This laptop came for repair because of the LCD screen backlight failure. My customer complained that the laptop LCD screen is black but the laptop works with an external monitor.
Here are my steps for troubleshooting this laptop with the backlight failure.
First of all, I tested this laptop with an external monitor connected to the VGA port and the external monitor worked absolutely fine. I was able to get crystal clear image on the external screen even though the internal screen didn’t light up. If the external screen works fine, then most likely there is nothing wrong with the video card.
Notebook display assembly diagram
After that I took a closer look at the laptop LCD and noticed that the screen is not completely black. The laptop screen still works but the image is very very dull, you barely can see it. It means that the screen still gets data signal from the video card, but for some reason the backlight lamp doesn’t work.
From my experience I know that this problem can be related the lid close switch, faulty inverter board or bad backlight lamp. I checked them one by one.
If you have a similar problem, make sure the lid close witch moves freely. The lid switch is a small button located close to the LCD screen. This button triggers the hibernation or sleep mode when the screen is closed. If the lid close switch is dirty, it might get stuck inside the laptop case and cut off the power from the inverter board. The inverter board works as a power supply for the backlight lamp and if there is no power coming to the inverter board, the backlight lamp will not light up either.
In my case the lid button worked properly, it didn’t stuck inside the case. When I was pressing on the button very fast, I was able to light up the screen but only for a fraction of a second. The image wasn’t bright and it had a pinkish tone. A pinkish tone usually indicates a problem with the backlight lamp, not the inverter board.
Even though I suspected the backlight failure, I decided to test this laptop with a new inverter board just in case. But it didn’t help. The screen didn’t light up even after I replace the inverter board. So, I was right, this problem is not related to the inverter board.
Finally, I disconnected the screen backlight lamp connector from the inverter board and connected my test backlight lamp (I removed it from another cracked screen). For the test purpose, you can buy a new backlight lamp here. Try to find a backlight with the connector already attached to it, so you can plug it into the inverter board. Make sure the connector on the backlight lamp is similar to the connector on your LCD screen.
As soon as I turned on the laptop, my backlight lamp lighted up. Yep, that’s the problem. The laptop screen has a faulty backlight lamp.
Here’s another laptop with backlight failure
This laptop video fails in a little bit different way. In this case the backlight lamp hasn’t failed completely.
The laptop starts with video on the screen but the background has reddish tone, the screen flickers and it makes noticeable buzzing noise coming from the backlight and inverter area. After a few minutes the backlight turns off by itself and the buzzing noise stops. When the backlight is off, the image on the screen is still visible but it’s very dark.
I removed the screen bezel and connected my test backlight lamp.
My test backlight works absolutely fine. The lamp doesn’t flicker and there is no buzzing noise. So, this laptop needs a new backlight lamp.
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January 19th, 2008 at 8:12 am
Hey there!
I am the owner of a Toshiba Satellite 5200-902.
The first weird behavior I noticed was the pinkish colors when my screen was just turned on and the colors were normal after a few seconds. I don’t remeber when was this behavior started, but I think it is at least for the last 2-3 months.
During the last week I had a flickering problem with my LCD screen.
Please check the following short video to see what I mean: http://video.google.com/videop.....5473598117
Sometimes, I could hear a whistling sound too!
My graphic card seemed to be ok since I could connect an external monitor and have no flickering to the external monitor.
So, it should be a problem with one or more LCD parts…
Since yesterday my screen turned almost totally black! I can hardly see the desktop.
However, the flickering seems to have stopped and I can still connect with an external monitor.
Do you have any idea what is that could be going wrong with my LCD?
I think there the following possibilities:
1. The problem is complex so the whole LCD needs replacement
2. The video cable needs replacement
3. The inverter that supplies the power needs replacement
4. The backlight bulb needs replacement
5. The inverter or backlight cable needs replacement
6. Other (please specify)
Please if you are familiar with my problem I would appreciate your help.
Thank you for your time reading my problem.
Andreas
January 15th, 2008 at 4:14 am
cj2600,
Lid close switch = ok
Inverter connections = ok
Still a dim display…
So back to the LCD assembly that I purchased that will not display anything, 1) it could be bad, 2) I could be doing something wrong… although I’m not sure what, or 3) it could be incompatible. Now that I think about it, it makes sense that the output from the video card needs to match the LCD panel. Will a 1024×768 panel work where a 1400×1050 once was? Thanks for the help.
January 11th, 2008 at 8:27 am
Bahula Smith,
First or all, check the lid close switch. It’s possible that the switch got stuck inside. Try tapping on the switch with a screwdriver, make sure it moves freely.
Second, it could be loose cable on the inverter board. I would try reseating cable connectors on both ends. I think it worth trying.
I would suspect the lamp failure too, I don’t think that you can damage the inverter by dropping the laptop.
January 11th, 2008 at 4:42 am
cj2600,
Yes, I purchased the whole LCD assembly. Lcd panel, inverter, cable, bezel, etc. I can’t get anything to display at all on the new assembly. I’ve tried changing several BIOS settings thinking that could be the problem, but still no joy!
BTW, what could be the problem with the old display? I am guessing since it was dropped that it is the bulb. The LCD panel is not cracked and still displays (although very darkly).
January 11th, 2008 at 12:43 am
Bahula Smith,
What do you mean by upper half, the whole display assembly with LCD, cable and inverter or just the LCD screen?
January 11th, 2008 at 12:26 am
It could be:
1. Loose connection on the inverter board, you’ll have to reseat cables on both ends.
2. Damaged backlight lamp (CCFL), in this case you’ll have to either replace the lamp (no easy) or replace the whole LCD screen (much easier but more expensive).
3. It’s possible that the inverter is dead but most likely you’ve damaged the backlight lamp.
Unfortunately, the only reliable to find the culprit is testing the laptop with another working screen.
January 10th, 2008 at 12:09 pm
I’m working on an Thinkpad A22m (2628-SSU) that was dropped. The LCD is displaying but only very, very faintly. I figured I could do an upper half replacement and ordered one from eBay. So far I have been unable to get the replacement to display anything. The damaged LCD panel is 1400×1050, while the replacement is 1024×768. Could that be the cause of my problems?
December 23rd, 2007 at 9:27 am
I’ve been having problems with my backlight too. I have a Toshiba Satellite Pro M40 and the backlight acts strangely. Sometimes it will work fine, other times it will come on after a minute or two, and other times it will come on if I f**k around on the computer’s monitor settings. It has been doing this for about a year but I can always get it working in a few minutes before. But for the last few days it hasn’t turned on at all no matter what I do. I’ve known for quite some time that it was my screen itself because I sometimes have to use a flashlight to see to get to the monitor settings. I don’t plan on taking it apart but I’m grateful to posts like these that can help me pinpoint the problem to tell the repair shop.
December 3rd, 2007 at 11:59 pm
Stefana Muller,
Here’s how I removed and disassembled the LCD screen on a Dell notebook. It’s not the same notebook but I can get the idea.
By the way, the backlight is located inside the LCD screen and in order to replace the backlight lamp you’ll have to take it apart. If you have no experience, you can permanently damage the screen.
December 2nd, 2007 at 12:21 pm
So, I have this problem with my Vaio PCG-K33 laptop. How do you remove the screen to replace the backlight lamp?