Screen backlight switches off randomly

I’m running Manjaro on an old (2008?) 13" Macbook. It worked brilliantly for a few months, until recently the screen backlight has started switching off randomly, usually within a minute of booting. A temporary hack to is to set the backlight off and on again with xbacklight, however it then turns itself off again almost instantly. I wonder if two drivers are fighting for control?

Things I’ve tried:

  • Adding the various acpi= options (none, native, vendor, video) in grub
  • Toggling ‘Handle display brightness keys’ and ‘Display power management’ settings in XFCE power manager
  • Upgrading kernel from 4.14 (was working fine previously) to 4.16

None of these have worked. When I used the acpi grub options there was still only intel_backlight listed under /sys/class/backlight/, although acpi appears to be installed and running. When the screen switches off, intel_backlight/brightness is equal to intel_brightness/max_brightness, and when I press the fn keys the brightness value in that file changes without any change to the actual backlight!

Any suggestions where else I could be looking? System details are below.

$ inxi -Fi
System:
  Host: r2-d2 Kernel: 4.16.14-2-MANJARO x86_64 bits: 64 Desktop: N/A 
  Distro: Manjaro Linux 17.1.10 Hakoila 
Machine:
  Type: Unknown System: Apple product: MacBook3,1 v: 1.0 
  serial: <root required> 
  Mobo: Apple model: Mac-F22788C8 v: PVT serial: <root required> UEFI: Apple 
  v: MB31.88Z.008E.B02.0803051832 date: 03/05/08 
CPU:
  Topology: Dual Core model: Intel Core2 Duo T7500 bits: 64 type: MCP 
  L2 cache: 4096 KiB 
  Speed: 798 MHz min/max: 800/2200 MHz Core speeds (MHz): 1: 1110 2: 1128 
Graphics:
  Card-1: Intel Mobile GM965/GL960 Integrated Graphics driver: i915 
  v: kernel 
  Display: x11 server: N/A driver: intel unloaded: fbdev,modesetting,vesa 
  resolution: <xdpyinfo missing> 
  OpenGL: renderer: Mesa DRI Intel 965GM v: 2.1 Mesa 18.1.1

How long will it run just showing the bios display?
Or boot some random Live-CD, and see how long it lasts.

If both of those also blink off, its probable the ccfl backlight tubes.

I’ve had machines like that where the backlight (one or two tooth-pick thin delicate florescent light tubes). I’ve even replaced the backlights on an old sony, and got a couple more years of use out of it.


Not for the faint of heart.

Or you can wrangle up a cheap LED monitor and set your bios to only use that.

Not likely as he is having a

Do you still have a mac os installed, it would be the best to see how is performing there?!
If not, try as was mentioned

A hardware failure would requiere a service.

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