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I booted a few minutes ago and everything was fine, update manager notified me about new updates so I decided to install them, and then poof, dim/dark screen is back in action.

I did update grub, I did tried to remve fglrx but terminal said I don't even have it installed and the "classical" fix I used is the

sudo setpci -s 00:02.0 F4.B=01

It does work, but only till I reboot, I had same problem but I added this code before exit 0 from /etc/rc.local [gksudo gedit /etc/rc.local] now it's still here but it doesn't work. I also tried nomode set before booting, it resulted in a crash.

Any ideas how to fix it? And I would also want to know if I can get completely the rid of this thing? It always came back when the computer was idle or when I tried to run things in full screen mode.

Other info: I run it on an Acer Aspire 5732Z with Intel GMA 4500M (graphics accelerator) if this helps.

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3 Answers 3

Just press buttons Fn+Left Arrow or Right Arrow while booting starts and that's it!

If its for acer laptop.

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oddly enough that worked for me! –  Nocturno Oct 9 '13 at 15:31

I was also having problems with suspend / resume in addition to the boot problem with a dimmed screen. The following 2 lines updated in /etc/default/grub fixed both of my issues.

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Be sure to replace vendor with your_machine_vendor and run sudo update-grub

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I have the same problem whenever I unplug an external monitor;

  • The first time I unplug, the screen is dimmed (at the same time as the screen/work areas are being reorganised, i.e. windows repositioned)
  • Then I re-plug the external monitor and unplug again, and the screen is getting full lighting back (is "un-dimmed").

Now lately, I have also realised that the screen is suddenly dimming even without using an external monitor. The dash, the shortcut line on the left hand of Unity have stronger lighting, as well as some pop-up windows. Whenever the screen is locked or the computer is in sleep mode, the display is showing full light strength for a moment as it returns to operating (after entering my password), then is dimmed immediately. It seems like the inactivity timer is never reset or something like that. Re-connecting power supply doesn't change screen lighting, and when re-connecting external monitor, the screen is dimmed there as well.

This is a Lenovo T500 laptop, Ubuntu 14.04 with Unity.

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