HP Probook 4515s Screen brightness stuck at lowest setting

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Hunzen

HP Probook 4515s Screen brightness stuck at lowest setting

Post by Hunzen »

Heya.

I have HP probook 4515s laptop where we installed Mint 16 "petra" 32bit.
While i was running this OS from the CD the screen were bright. After installing screen does have gone dimm. In the boot screen is bright but when the OS loads it goes dimm.

When pressing FN + Brigtness up there is actually picture of brightness going up but it does not change the brightness.

I have tried several fixes in this forum. Even xbacklight what did not do anything... Even when set to maxium. Once i however did get screen bright but screen were bright for the second and then it went to dimm.

I tested even from screensaver/lockscreen settings and took off dimmening for powersafe but did not change anything.
And sorry if i have missed anything. Not used to ask help from the forums.

Is there way to force it bright at each boot or is there way to fix FN key commands?
Last edited by LockBot on Wed Dec 28, 2022 7:16 am, edited 1 time in total.
Reason: Topic automatically closed 6 months after creation. New replies are no longer allowed.
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roblm
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Re: HP Probook 4515s Screen brightness stuck at lowest setti

Post by roblm »

Did you try testing these kernel parameters?:
acpi_backlight=vendor
acpi_osi=Linux
acpi_osi=Linux acpi_backlight=vendor
acpi_osi='!Windows 2012'
acpi_osi=

You can test them first without making a permanent change. The effect will only last for one session. At the GRUB boot menu select the correct line but don’t press Enter. Press the “E” key to edit. If no menu shows then hold down the shift key while starting. Using the arrow keys, go down to the line that starts with:
linux /boot/vmlinuz..............ro quiet splash $vt_handoff

Add a space to the end of the line and then add the parameter → acpi_backlight=vendor
Press F10 to start your system and test the brightness keys. Then test xbacklight by opening the Terminal and typing these commands to see if the brightness changes:
xbacklight -set 100
xbacklight -set 50
Repeat the process with the other parameters and also testing xbacklight each time.

If one of the parameters fixes the brightness control then make the change persistent. In the Terminal type this command:
gksudo gedit /etc/default/grub

Change the line: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
by adding a space after the word “splash” and then add the parameter that worked.

Save the file and then type this command in the Terminal: sudo update-grub

If the steps above fail then open the Terminal and type this command and post the output:
ls /sys/class/backlight/*/* | grep brightness
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