Your IBM ThinkPad laptop screen (or any other laptop) went blank? Check out this article.

I could get the screen to come back on momentarily by toggling Fn-F7 a few times, but after about 10 seconds it went blank again. After rebooting, same thing — 10 seconds and blank.
Upon closer inspection, I noticed that I could actually see the windows very, very dimly on the screen. However, it was so faint I couldn’t see a cursor or read any text but the screen was definitely trying to project the image. So I hooked up an external monitor and the image displayed just fine.

The author of the above mentioned article article tried replacing the screen inverter board first but it didn’t help. After that he replaced the LCD screen and this resolved the problem.
From myself I would like to add a few more tips for troubleshooing and resolving laptop backlight problems.
Let’s say the laptop screen went blank but you still can see a very dim image on the screen. An external monitor connected to the laptop video port works fine.

Here’s what you can try:
1. Check the display close switch - a small button located close to the left hinge. Make sure this switch moves up and down without any problem, try tapping on the button. When the button gets stuck in the “closed” position, it cuts off power from the inverter board and the screen will be black. Tapping on the display close switch can help to turn the screen back on.
2. Try reseating connectors on the inverter board. The screen can go black when it’s not making good connection with the inverter board.
3. Replace the inverter board.
4. If replacing the inverter board doesn’t help, probably there is a problem with the backlight lamp inside the LCD screen. It’s possible to replace the backlight lamp without replacing the whole LCD screen, but it’s not easy. Here’s how you can find a new backlight lamp for your laptop.
5. If you cannot replace the backlight lamp you’ll have to replace the LCD screen.
6. If all above mentioned steps do not help and the screen is still black, your problem can be related to a faulty video cable or bad motherboard.
You’ll find IBM laptop disassembly instructions in hardware maintenance guides.
You can use these troubleshooting steps for any laptop.