01-30-2015 03:24 AM
I bought a Thinkpad X240 a few months ago, it was working perfectly except the know bug of the "bottom left corner" which happened a few times.
But a few days ago, the screen backlight suddenly stopped working. I put it to sleep, I came back home, I opened the lid and the screen didn't light up.
The screen itself works perfectly (if you put a light on it you can see what's displayed), and there's no other problem.
This doesn't seem to be a software problem since I doesn't work in the BIOS, nor in Windows or Linux..
Why does the backlight would suddenly stop working ?
Thanks in advance,
11-30-2017 07:52 AM
Same here. The backlight is out in the bios as well so I believe mine is a hardware problem.
For other thinkpads, I find people saying this is a surface mount fuse on the motherboard and can be "fixed" by bridging the fuse with solder. But I can't find a fuse near the display port that is bad. The most likely fuse I find is F2 on the backside of the board near the display port, but it doesn't measure as an option circuit so I don't think that one is bad.
I will probably buy another broken laptop and swap parts.
11-30-2017 09:10 AM
There are 2 likely, possible causes.
failed Hall sensor (magnetic switch inside the lid that senses when the lid is closed)
If the laptop is set to sleep when the lid is closed, you can test the sensor with a magnet. You can usually find the magnet by moving a little screw around on the palmrest. The screw will snap to the magnet when it gets close. the sensor will be inside the lid near where it will hit the magnet when you close the lid. If you run the machine with an external monitor, moving a little magnet near the switch should put it to sleep. If it doesn't, you may have a failed sensor.