Do you have a problem with the backlight on your laptop? If yes, you are not alone, that’s one of the most common laptop problems. In most cases the screen inverter is the culprit. Here are some LCD screen backlight failure symptoms that could be related to a bad inverter board:
- Laptop boots as usual but after some time the screen blacks out. You still can see an image on the screen but it’s very dim. You might even use a flashlight to see it better. Sometimes the backlight comes back for a while but then goes off again. In some cases you can turn the backlight on if you tap rapidly on the lid close switch.
- The screen always stay black and the backlight never comes on but you still can make out an image on the LCD. It’s dark, but the image is still there.
-In some cases you might hear a buzzing noise coming from the area where the inverter board is located, it’s on the bottom part of the display assembly.
NOTE: if you cannot see an image on the screen, most likely you have a different problem and there is nothing wrong with the screen inverter.
Other related articles:
Laptop has bad video on the LCD screen. What is wrong?
Notebook display assembly diagram. How image appears on the screen.
How to troubleshoot and fix laptop video problems
How to replace laptop backlight lamp (CCFL)
Here’s an example of replacing the FL inverter board on an IBM ThinkPad T41 notebook. This guide will work fine for any other IBM notebook. Replacing screen inverter on other notebooks like Dell, HP, Toshiba, etc… will not be much different.
First of all, unplug the AC adapter and remove the battery.
In order to access the inverter board you’ll have to remove the LCD screen bezel. On most laptops screws are hidden behind screw seals. In this case we have 5 screw seals on the front. Carefully remove the seals with a sharp object and glue them on the LCD bezel, in this case you will not lose them. Remove all screws and mark them somehow so you are not confused when you assemble the notebook back.
Some laptops also have screws on the side of the display. This notebook has 3 screws on each side. Remove screws seals and then remove screws.
Start removing the LCD bezel with all fingers. Carefully wiggle the bezel to release plastic latches. Never use any sharp object during disassemble because you can accidentally damage the screen.
If latches are very tight you can use a guitar pick to unlock them. Insert the guitar pick between the LCD bezel and cover and carefully move it alone the side.
This notebook allows you to replace the inverter board without removing the LCD bezel completely. Lift up the bottom part of the bezel and remove one screw securing the inverter board to the LCD cover. This location is very common for the screen inverter. On most laptops you’ll find it under the display bezel below the screen.
Carefully lift up the FL inverter and rotate it a little bit. Unplug cables on both sides. The left side of the inverter board connects to the video cable, the right side to the backlight bulb (CCFL tube) inside the LCD screen. Remove the inverter and replace it with a new one.
To find a new inverter board (and any other spare part too) for any IBM notebook you should use the FRU number from the part.
If you find this article useful, please consider making a donation to the author. Thank you!
February 2nd, 2009 at 8:32 pm
radiator,
It’s hard to tell what’s going on with your laptop. Could be bad connection, defective cables, some kind of grounding issue, etc…
I think it’s necessary to remove the screen bezel and find out which part you have to move or touch in order to kill the backlight. If the backlight goes off when you move the cable, it’s either bad connection between the cable and inverter or the cable is defective.
February 2nd, 2009 at 8:27 pm
Judy,
From my experience, if the external monitor works MOST LIKELY there is nothing wrong with the video card.
It’s possible the inverter board was defective and has to be replaced again.
February 2nd, 2009 at 1:49 pm
What if plugging an external monitor into the VGA port works fine – does that still mean the inverter board might be bad?
February 1st, 2009 at 5:18 pm
394cj2600 Says:
January 26th, 2009 at 11:17 pm
Brian,
What is interesting is that connector to the left, facing machine, the one with 4 or 5 little connections – if I “wiggle’ it, or just barely attach, the display comes on but then goes again – almost like it’s a short or something but I can’t figure how to troubleshoot it.
From the description it sounds like there could be a problem with the cable, not the inverter.
You’ve replace the inverter two times, but still experiencing the same problem. At the same time you cam make it work if you wiggle the cable? Sounds like a bad cable to me.
***************
Can I purchase this cable somewhere? I’m not sure how to google that….
January 31st, 2009 at 7:33 am
Hi there
I am the owner of T41. When I touch left or right bottom part of ma LCD the bulbs go blind and I barely can sse the windows desktop. I can see what is going on. When i touch the upper part of my lcd and move it up and down nothing bad happens. When I touch near the inwerter and start moving the lid I hear buzzing sounds from the inverter place and then the lcd becomes dark, bust still it is possible to see the desktop. My friend says it the lcd cable but from the above posts it seems to me it is the inverter. What do you think?
And one more thing. I could work without any interference yesterday when moving the lcd lid. It only happens when I move the lid.
thx
January 30th, 2009 at 12:42 pm
I have had recurring problems with my laptop screen. 6 months ago the screen went dark (but picture still dimly visible) and I was told the problem was the cable, it was replaced and I was good to go. For 6 months. The screen went out again (still dimly visible), the inverter was replaced, and the screen worked for a day. When the screen went dark again (still dimly visible), I took it back to the computer shop – they kept it for a week, then told me that the video card was bad, it would be very expensive to replace, and I would have to replace the whole motherboard. He then suggested just connecting the laptop to an external monitor. Which I did. Works fine. But another tech I happened to run into, said that if the external monitor works, the video card is fine, and the original tech must have put in a defective inverter or missed a cable problem. Before I take it back to the original technician, does the opinion of the 2nd tech make sense? Any help greatly appreciated.
January 26th, 2009 at 11:17 pm
Brian,
From the description it sounds like there could be a problem with the cable, not the inverter.
You’ve replace the inverter two times, but still experiencing the same problem. At the same time you cam make it work if you wiggle the cable? Sounds like a bad cable to me.
January 26th, 2009 at 11:14 pm
frank,
If the screen is black but you can see the lines, it’s not the inverter. When inverter fails, you barely can see anything.
You’ll have to test the laptop with an external monitor and check the external video.
1. If the external monitor works fine, most likely you have either bad LCD screen or defective video cable. For some reason I think your problem is related to the cable, but I could be wrong.
2. If both the internal LCD and external monitor display same lines, most likely your problem is related to the video card. I guess in your laptop the video card is integrated into the motherboard, so it’s a bad motherboard.
First of all, test the external video output. It will help to narrow down the problem.
January 26th, 2009 at 11:10 pm
Colleen,
Not sure 100% what’s going on but I think the backlight lamp is failing. I think one day it will not light up at all. That’s just a guess.
January 26th, 2009 at 11:08 pm
Mo,
Is it dim like there is no backlight at all, or dim like the backlight works but it’s not bright enough?
Did you check the laptop power settings (usually found in control panel)? Maybe the screen brightness is set to minimum for the battery mode?