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I have two X200 Thinkpads. They both have the rather annoying problem that, unless the display backlight is set to its maximal value, it emits an unbearable noise. The odd thing is that one of them boots with the max. value and the other does not. It is also impossible to set the second computer's display to the max. brightness value by using the brightness-up button (it will only reach 779942 of 846600). I have to

cat /sys/class/backlight/intel_backlight/max_brightness >/sys/class/backlight/intel_backlight/brightness

Now the sound goes away but only until the next reboot. Is there anything I can do to make the brightness value persistent across reboots?

PS. I understand that I can run a script on startup, but something is making my first comptuer different and I would like to know what. I have tried this using the exact same OS (the same live USB), and both computers have the same BIOS version (from 2012; 7.22?) and settings. The difference is also there in the BIOS setup, before loading any OS.

(PS II. I might add that the problem does not exist in Windows, even with the screen dimmed.)

marked as duplicate by Fabby, elbarna, ilkkachu, Kiwy, Archemar Mar 12 at 15:19

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  • My guess is that you can set the display brightness in the bios setup. Config -> Display -> Brightness -> High/Normal (I don't have an X200 right now, but that's the option on an X61). The buzzing sound is most likely a dying inverter. Your displays are non-led, right? – Freddy Mar 9 at 11:25
  • @Freddy, my only option in config/display is 'boot display device', which is set to 'thinkpad lcd'. so do you think this will go away if i replace the inverter? – Toothrot Mar 9 at 11:39
  • @Toothrot Damn, the brightness option is already gone like on all newer Thinkpads. Yes, if it's not the inverter, then it's an issue with the CCFL (usually getting darker until it sometimes fails). But an inverter swap is not so complicated and they're cheap nowadays (ebay). See here and here. – Freddy Mar 9 at 11:52

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