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I use a laptop. When I take the power cable out to run on batteries, the screen darkens, as it is no longer so bright, to save on battery power.

When I put the power cable back in, the screen brightens back to it's original brightness.

However, I have since replaced the power cable, and the screen remains darkened.

How do I regain the original brightness?


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migrated from Apr 15 '10 at 5:51

This question came from our site for system and network administrators.

What operating system are you running? What laptop model is it? – Wesley Apr 15 '10 at 5:53
up vote 0 down vote accepted

Depending on your operating system, you will need to go into the control panel that controls power options. For example, in Windows it's called fittingly enough "Power Options". From there, look for an option to edit the brightness of your laptop screen. Without knowing more about what OS you're running, I can't be more specific than that.

There's also another method for changing the brightness of your screen. Somewhere on your laptop keyboard will be two keys with icons that probably look like a sun or computer screen with a plus/minus or up/down arrow next to it. Those keys are the brightness toggle. It will probably also be in a different color from most of the other keys. Once you've found that key you need to find a "Function Key". It will probably be printed in the same color as the brightness icon is in. It will say something like "Fn", "Funct" or something similar. When you find the function key, press and hold it while tapping the brightness keys.

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Brilliant. The keyboard brightness keys did it.

My cat has been lying on the warm laptop keyboard.

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Super! Glad it worked out. You can upvote a question and also mark it as the answer so others know what worked. =) – Wesley Apr 15 '10 at 16:33
How do I mark it as the answer? There are no controls that I can see. – Steve Apr 15 '10 at 20:59
if you go to your user profile to the accounts tab, you can associate your Super User account with your Server Fault account. That will give you access to accept an answer on this question. – Stephen Jennings Jun 12 '10 at 6:18

How long have you used the battery? If the battery has been used for 1~2 years, then the voltage of the battery will be much lower.

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