Ben zelf ook nog even verder wezen zoeken op het Engelse forum. Hier de oplossing gevonden.
QUOTE:
Re: Acer Aspire 5749 screen brightness
I confirm, with the new kernel and update to the grub configuration the brightness buttons work.
To use this fix
Update your system
Code:
sudo apt-get update
sudo apt-get upgrade
Edit the kernel load parameters:
Code:
sudo gedit /etc/default/grub
There change the line starting as:
Code:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash ... so on ... "
adding a space before the closing quote" and a parametter setting
acpi_backlight=vendor
I had this line:
Code:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.i915_enable_rc6=1 acpi_backlight=vendor"
Save the file, exit the editor.
Update GRUB
Code:
sudo update-grub
Reset your PC. Should work!
I thank everyone for help very much!
EINDE QUOTE
En het werkt.
Nogmaals heren bedankt voor jullie meedenken en de moeite.