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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August 26th, 2009 at 11:27 am
Toshiba Satellite M35X-S349 laptop has a pink line in LCD. Replaced the LCD with 3 compatible LCD’s, and all 3 had bad backlight.
I have 6 different M35X inverters (K000018860) which I swapped out with each LCD, and they all did not resolve the problem.
If I put the original LCD (with the pink line) into the laptop, there is no backlight problem and all 6 inverters test ok.
What the heck is going on?? I pushed the white button many times and did not solve anyything.
Any help would be appreciated.
August 16th, 2009 at 3:45 pm
Dell Latitude C800 LCD problem intermittent, no 100% indicative of back light or inverter failure so I am wondering if the LCD screen could be faulty? The machine will run well for days and then this will crop up again. I’ve run an external monitor successfully to rule out adapter problems.
Symptoms:
Screen has consistent thin blue line vertical line/drop out
along right part of screen…a second similar line will appear on left portion of screen, with minute stress on lid when adjusting then disappear.
The entire screen/or horizontal portions will distort/if by static, screen resolution/color rendering will suffer concurrently.
The only sign of back light failure (after educating myself via this site) is infrequent and very brief screen flickering from full illumination to black out…nothing in between.
July 19th, 2009 at 12:54 am
thanks a lot, very useful your tips and the information posted. again thanks for your time spended and sharing your experience..
July 15th, 2009 at 3:03 pm
Thanks, this info helped me to fix my qosmio x307-q705.
July 4th, 2009 at 10:02 am
Hi! i have a presario v2000 which is starting to turn reddish on me and then turns back to it’s normal color. i did all the troubleshooting(after watching your videos)just to make sure it wasn’t the video card or the inverter, so my guess that it’s the bulb. any suggestions on where i can but the bulb? thanks for your help.
June 9th, 2009 at 1:23 pm
help please!
i broke my screen on my aspire 3630 so i bought and fitted a new one,but i cant get the backlight to light.windows loads up as normal but without backlight.i have tried the lid switch and this appears to be working fine(windows goes to standby)
i have changed the inverter and tried the screen in another laptop and it works fine.so i tried to connect it to a external monitor but it only goes as far as windows xp is loading then,external monitor goes off (no signal),but the laptop screen loads up as normal without backlight!
any suggestions gratefully accepted.
thanks
andy
June 6th, 2009 at 8:02 pm
[...] Check out my previous post about troubleshooting laptops with backlight failure. [...]
June 4th, 2009 at 6:40 am
I have the same prob with my 1.5 year old dell 1501. what does that cost to replace the backlight?
May 29th, 2009 at 11:20 am
I had the same problem with my DEll Inspiron 6000. The monitor went totally dark. I was not sure if it was the inverter or the backlight. The monitor was bright for a couple of seconds when the DELL logo pops up, and then went dark. There was no reddish tone on the screen and so I guessed that it was the inverter (which is much easier to replace compared to the backlight). Replacing the inverter worked for me and it only cost 10 bucks.
May 27th, 2009 at 6:16 pm
i think i have a similar problem, when i turn my laptop on the screen is up briefly, but it just goes black. if you hold it at a certain angle you can faintly see the background it is just so dark it appears black. i have dell xps about 3 years old..any idea if it would be the screen inverter board or something more serious?