backlight on laptopscreen will not turn on

[Yarnil]

Hi everyone,

Im using an Acer laptop and the backlight will not turn on using Kubuntu 11 and 12.04. It works on 10.04. If I put an external (CRT) monitor on it, it works.

By using the command: <quote>sudo setpci -s 00:02 F4.B=0</quote> I will be able to turn on the screen (Thank google for that) but how can I make the latop have a screen without the use of an external screen first?

Thx, Yarnil

[Teunis]

I'm not able to give the ready recipe but it's likely along the lines of putting this as a script in an autostart file.
Go to the System Settings and select start up and add a 'program' meaning this script.

[oshunluvr]

This could be an ACPi issue. First, be sure your power setting in the system menu are correct - meaning your monitor is set correctly.

The above backlight command can be put in /etc/rc.local.

Try amending acpi_osi=Linux acpi_backlight=vendor to the GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" in /etc/default/grub, in other words and the acpi... bit behind quiet splash inside the quotes.

Then run "sudo update-grub" in a terminal and reboot.

[Yarnil]

Hi,

Teunis, can you tell how to do that? It needs sudo and I cant type the password if I cant see what the system asks of me. Or is it save to put it in the script too, and how?

Oshunluvr, I tried to amend that line into the grub file, and at first the screen's backlight stayed on longer, but went out after a few seconds. Any other ideas that might work?

Thanks for your time.

[bra|10n]

Hi,

Teunis, can you tell how to do that? It needs sudo and I cant type the password if I cant see what the system asks of me. Or is it save to put it in the script too, and how?

See this link...

Oshunluvr, I tried to amend that line into the grub file, and at first the screen's backlight stayed on longer, but went out after a few seconds. Any other ideas that might work?

Thanks for your time.

You did remember to run,

sudo update-grub

in a terminal?

[Yarnil]

@Bra|10n: thanks for the link. I will try this tonight after work.

And I did run sudo update-grub, but knowing my skills, I will havescrewed up something

[oshunluvr]

You didn't say whether adding setpci -s 00:02 F4.B=0 to /etc/rc.local worked or not. Also, the exact model of your laptop and video card would help.

[Yarnil]

Oshunluvr, I tried it, but it didnt work. Its an Acer Aspire 7715 with 4Gb of ram.

Bra|10n, I tried the link but it didnt do the trick.

Anyone has another idea? I will try the instructions in the link later again (Dont havem uch time now) but any help is welcome. Thanks in advance.

[Yarnil]

Ok given the link another try and figured out that I forgot to get the part quite splash out of the start script (Shift, E, remove quite splash, add ACPI_OSI=linux, F10) and it worked. Thanks all, I now have a functional laptop again, that doesnt need an external monitor.

[Yarnil]

And another update. (Sorry for the high newbie-ness I am displaying. )

It works when I restart, but if the screen goes black for a reason, the backlight stays off. Restart or an external monitor and running the line sudo setpci -s 00:02 F4.B=0 is the only thing I can do then.