Troubleshooting laptop with backlight failure
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.
Entry Filed under: LCD Screen Repair
67 Responses to “Troubleshooting laptop with backlight failure”
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Pages: [7] 6 5 4 3 2 1 » Show All
June 14th, 2008 at 5:34 pm
[…] First of all, take a closer look at the LCD screen. Look at the screen under bright light. It’s possible that the image is still on the screen but it’s very faint. If that’s the case, check out these tips for troubleshooting laptop with backlight failure. […]
May 3rd, 2008 at 7:19 am
my laptop Aspire acer 7620 bios setup was passworded by my younger brother, And he has forgoten d password and operating on d laptop as corrupted,and there is nothing i can do than to boot to the cmos setup and setup the boot option to load another operating system.and have tried all the master password that i know none of it solve the problem .now i dont know what to do either to go for a new laptop or i should try other site for help.please if anyone can solve my problem i promise to be his or her friend forever.i also i’m an engineer and i’m fed up with it.THANKS.MY LAPTOP IS A PHOENIX MAKER.
May 1st, 2008 at 11:32 am
I am having LCD issues with a Dell Inspiron 6000 laptop. I have replaced the inverter initially, and tried replacing the bulb with no success. There is still a ghost image on the original screen, and the laptop works fine with an external monitor attached. I finally broke down and got an aftermarket LCD screen, which works but is very
dim compared to the original. When I check display settings it lists only “multiple monitor” configurations and I can’t seem to find a way to reset to just the built-in monitor. It has an ATI graphics card which supports and changes multiple monitor settings, and under devices there is a “mirror” monitor device also. Any ideas whether
going to single monitor configuration will allow adjustment to a brighter screen setting, or could cabling or motherboard issues
be involved? Thanks for any help.
Ken Cotton
April 16th, 2008 at 1:26 pm
it songs good so i am going to try it to see if it work on my dell laptop.
thank you.
April 12th, 2008 at 8:38 am
I’ve got Toshiba M70 with a slightly different screen problem. Everything works fine on an external monitor but with the laptop screen, at first it appears the screen is dead. The screen remains black when booting up, but if you look closely, it is noticable that there is light behind the screen, I just wasn’t getting an image. I started poking around and found that if I squeezed the top left corner of the screen, I got a nice bright image and the computer was working fine, my thumb gets really tired while surfing though. It has to be some sort of connection problem, but I just can’t find it.
Any idea’s?
March 26th, 2008 at 8:53 pm
Frank,
This is not related to inverter or backlight.
To me this sounds like a problem with the LCD screen itself.
Take a look at this post. You screen looks similar to examples 5 and 9, right?
March 25th, 2008 at 5:48 pm
I Don’t think my screen problem is related to an inverter or a backlight. When I fire up the computer my screen flickers and depending on how I move the screen up and down it gets better/worse. I have a 1.5″ area top to bottom on Left hand side which remains uneffected but the rest of the screen is distorted. I took it apart and when I tap the top back of the screen with my finger it replicates the problem. This area is near the cable and the Green circuit board.