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 (not even very dim image), 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.
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June 18th, 2008 at 10:02 pm
Enigmaniac,
This problem could be related to:
1. Screen inverter.
2. Backlight lamp (CCFL lump) inside the LCD screen.
3. Video cable.
4. Motherboard.
I think the magnetic lid switch would be the last think to blame. I’ve never seen a failed magnetic switch. Maybe I’m lucky.
You should ask the technician how he came to that conclusion. If he tested your laptop with another known good LCD screen and inverter, most likely he’s right. Also, this problem could be related to the video cable.
If you have a magnetic lid close switch, you have to have a magnet somewhere inside the LCD panel. This magnet activates the switch when the display is closed. Find a small metal screwdriver and move it slowly along the LCD screen bezel. The screwdriver will be attracted by the magnet. Now when you know where the magnet is located, close the display and find the location of the magnetic switch.
Try reducing the LCD screen brightness as David did in the comment 279. I guess you have a different key combination for a HP laptop. On my HP Pavilion zv5000 I use Fn+F7 to reduce the screen brightness and Fn+F8 to increase the brightness.
The only reliable way to narrow down the problem is installing another inverter and LCD screen. Talk to your technician and ask what he did. If he tried that already, you may try replacing the video cable. If replacing LCD, inverter and video cable will not help, apparently you need a new motherboard.
June 18th, 2008 at 9:36 pm
David G,
Here’s my guess. If you are getting the same problem with another inverter board, most likely it’s not related to the inverter. Apparently, the backlight lamp is getting old but it still works when you lower the voltage (reduce the screen brightness). I just tried reducing the screen brightness from 7 bars to 5 bars on my ThinkPad T42 and looks OK, it’s still usable.
June 18th, 2008 at 2:48 pm
Hi,
I have an HP dv6157ea notebook. Some days back the display started flickering and after a day or two it went totally dim. It seems that the backlight is turned off as I can still faintly see my desktop if there is enough light focused on it.
I took it to a local computer repair centre who say that its a motherboard problem and the entire motherboard needs to be replaced! However, when I connected an external monitor, it works fine. So I’m sure its not a motherboard issue.
I’m pretty sure that its something to do with the magnetic display lid switch as I have tried replacing the inverter.
Any ideas on how can I find the switch in the laptop and replace it?
Many thanks!
June 13th, 2008 at 5:22 am
Thank you for this site and your input. This is a continuation of post 275 + 274. I have not sent back the replacement inverter board and have kept it installed. I have lowered the screen brightness with the function keys (Fn + [home or down]), to 5 bars of 7. For a few days now the screen works normally, with not one outage. Can I consider it fixed? What was (is?) the probable problem?
June 11th, 2008 at 1:36 pm
Joe Beene,
If the LCD screen had been cracked, you cannot repair it. You’ll have to replace the whole LCD screen.
June 10th, 2008 at 7:29 am
i have a ibm thinkpad laptop it latter says resource conflict-allocation error static node #01, i changed the battery the message continues what can i do to rectify that
June 9th, 2008 at 4:10 pm
Part of the screen is black and part shows the screen. It looks shattered around the edges of the black.
Can this be fixed or do I need to replace the screen
June 6th, 2008 at 6:55 pm
David Goldman,
It’s possible that you got a defective inverter. If after replacing the inverter again you still have the same problem, most likely it’s related to the backlight lamp (CCFL), apparently it’s getting old. The backlight lamp is located inside the LCD screen, on the bottom. It’s possible to replace the backlight lamp at home, as I described in this post, but it’s not easy and there is a chance that you can damage the LCD screen. The best way to go is replacing the whole LCD screen. If you have nothing to lose, then you can try replacing the backlight lamp, you can find it online for $10-15.
June 6th, 2008 at 2:47 pm
I have an IBM thinkpad T42. I have a problem exactly like discribed for a bad Screen Inverter.
After a short while ( 5 to 40 min) the screen goes very dim as discribed. No lines no buzzing. This while on battery, when plugged in screen goes dim within a few secs to mins.
Works fine with external monitor. I can restore sceen for a short while by toggleing though the ext monitor function (Fn + F7).
I did get a new inverter (FRU 26P8464) from bestcompu.com on ebay. It does the the exactly same thing. They will replace or refund.
Could it be another problem?
June 5th, 2008 at 10:54 pm
RAJDEEP,
You can try restoring the laptop back to the previous restore point (when the sound was working fine) using Windows System Restore utility.