The dreaded failing backlight

My Thinkpad T42 is getting quite old now and well used. A week or so back it started having a pinkish tinge to the screen when you turned it on or resumed it. The pink colour eventually disappeared after about 30 seconds and became the usual white. However, last Saturday the backlight decided to fail completely. Well almost fail. With the laptop on full brightness after turn on, the backlight would turn itself off after a few seconds. If I turned the brightness down a notch then the backlight would stay on. Not a great solution as my display has been getting rather dim anyway.

Now, a friend gave me a 14 inch LCD panel out of a broken laptop some time ago. It has a 20 pin interface connector, and most modern panels use 30 pin connectors (including the T42). So it sat gathering dust. However, I wondered whether the backlight out of that screen would work in my T42’s screen. I did some googling on ‘CCFL replacement’ and found enough info to have a go. It looked like most laptop screens use a very similar long thin (about 1 or 2mm diameter) flouro tube that runs along the bottom of the screen. They sit in a sort of U shaped reflector and hence reflect light up into the screen.

These flouro tubes are easy to break. Remember they are long and thin and made of glass. Fortunately I didn’t break mine.Most LCD panels also seem to be designed to make it difficult to remove the CCFL tube. I know I had several attempts and you do have to contort things and hope nothing breaks.

But eventually I had both out.Now, the tubes tend to have some kind of rubber mounting on the ends to make sure they don’t sit directly on the reflector. The rubber bits from the broken laptop screen were different to the Thinkpad ones. Originally I tried to ‘make it fit’ using the new end bits … but this was a bad idea. Basically I had wires where the Thinkpad wanted screws to go through, so I ended up removing the rubber bits using a knife so that I could replace them with the original rubber end stoppers on the Thinkpad. I also ended up resoldering wires to one end of the CCFL tube. If you read other notes on the net, you’ll note that you’re not meant to solder too close to the end of the tube. Thats probably a smart thing to do as the voltages to the tube are very very very high.

Trying to get it all back together proved difficult and I had many attempts and in the process distorted the U shaped reflector. Basically when I did get it going (so, yes it did actually work), I ended up with uneven lighting and some whitish glows at a few points along the bottom of the screen. I also have a problem where the backlight shuts itself down if its running on full brightness for a few minutes. Thats a worry. However, it runs fine on lower brightness levels and the screen in general is brighter so its not a problem running it on lower brightness.

So its not a complete success. Its useable for now, and ultimately I think I’ll try and find a replacement panel.