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Thread: backlight won't come on, on lemu1

  1. #1
    Join Date
    Jul 2006
    Beans
    15

    backlight won't come on, on lemu1

    Suddenly on my Lemur UltraThin lemu1, the backlight is not turning
    on, so when I boot I get a black screen. I can just barely
    make out that the login box is displaying on the screen,
    but it is essentially invisible without the backlight.
    If I plug in an external screen or log on remotely,
    the machine seems normal.

    I am running Ubuntu 11.10 (oneiric ocelot) and have updated the
    System76 drivers.
    Using the function keys to change the brightness has no effect
    on the laptop screen.

    What can I do? Thanks.

  2. #2
    Join Date
    Aug 2006
    Location
    Monterey, CA
    Beans
    367
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: backlight won't come on, on lemu1

    Assuming it's not a hardware issue try this

    Code:
    cat /proc/acpi/video/VGA/LCD/brightness
    Where VGA, and LCD is the directroy for your monitor.

    The vaules returned should look something like this:

    Code:
    levels:  12 25 37 50 62 75 87 100
    current: 100
    Then you just want to change the vaule to whatever you want, ie.

    Code:
    echo 75 > /proc/acpi/video/VGA/LCD/brightness
    Did that work?

  3. #3
    Join Date
    Jul 2006
    Beans
    15

    Re: backlight won't come on, on lemu1

    Thanks to Lee_Machine for the suggestion, but I don't have a
    /proc/acpi/video directory. Should I?

    However I seemed to have solved the problem. Although rebooting
    did not help, I tried shutting down, removing the battery, and
    rebooting on AC power only. This time the backlight came on as normal
    (a relief, I was afraid it was a hardware problem). Then I popped
    back in the battery, and now it seems normal (I can boot with
    battery in).

    I have no clue how it got messed up, but it seems to be fine now.

  4. #4
    Join Date
    Apr 2005
    Location
    USA
    Beans
    Hidden!
    Distro
    Ubuntu Development Release

    Re: backlight won't come on, on lemu1

    I have HP pavilion dv6000 laptops. Sometimes (not frequently) the screen is black when I turn on the computer.

    I immediately turn off the computer, remove the battery and AC connection. After that I keep pressing the ON (power) button for 60 seconds.
    Next, just plug in the battery and the AC back.
    And voila! the laptop works.

    I've learned this trick on many websites when searching for "black screen"

    If

    Here are some samples:

    http://forums.computers.toshiba-euro...threadID=55606

    http://getsatisfaction.com/hp/topics...reen_6mths_old

    http://getsatisfaction.com/hp/topics...reen_6mths_old


    A video uploader asking for help on the same issue. See the the comment by "LassiPKTunn" on the video:

    https://www.youtube.com/watch?v=g3hF8k6W4YU
    Last edited by ubuntu27; December 18th, 2011 at 05:56 AM.

  5. #5
    Join Date
    Aug 2006
    Location
    Monterey, CA
    Beans
    367
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: backlight won't come on, on lemu1

    Sorry about that. I haven't been using Ubuntu for quite sometime and just recently starting using xubuntu as my main since I don't feel like rebuilding Arch right now

    Anywho, it appears things are different in Ubuntu...no surprise there. I found how it's done now via command line, well one way.

    Code:
    sudo chown "username" /sys/class/backlight/acpi_video0/brightness
    Code:
    sudo chmod 777 /sys/class/backlight/acpi_video0/brightness
    This allows you to change the video settings. To make sure the numbers are the same as mind do this:

    Code:
    cat /sys/class/backlight/acpi_video0/brightness
    At max mine is set to 7 by default; which you can change that to. So to change the brightness up and down do:

    Code:
    sudo echo  7 > /sys/class/backlight/acpi_video0/brightness
    Where 7 is the highest you can go unless you change the max_brightness file.

    Did this work for you?
    Last edited by Lee_Machine; December 18th, 2011 at 08:21 PM.

  6. #6
    Join Date
    Oct 2007
    Location
    Aurora, CO
    Beans
    2,543
    Distro
    Ubuntu

    Re: backlight won't come on, on lemu1

    Quote Originally Posted by dnarnold View Post
    Thanks to Lee_Machine for the suggestion, but I don't have a
    /proc/acpi/video directory. Should I?

    However I seemed to have solved the problem. Although rebooting
    did not help, I tried shutting down, removing the battery, and
    rebooting on AC power only. This time the backlight came on as normal
    (a relief, I was afraid it was a hardware problem). Then I popped
    back in the battery, and now it seems normal (I can boot with
    battery in).

    I have no clue how it got messed up, but it seems to be fine now.
    I'd keep a close eye on this. The backlight shouldn't have any issues on a LemU1 on 11.10, so my guess is that this is some sort of hardware problem. If this happens again, and you can't get it to work, go ahead and send us an email and we will get it taken care of.
    Ian Santopietro - System76 Technical Support.
    Open a Support Ticket!
    Ask a Sales Question!

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