My laptop screen brightness just keeps on increasing and decreasing in a loop.

Is there some setting that I have messed up? I am sure the machine should be okay, because it is pretty new still.

I am using Windows XP, and the machine is a DELL Latitude E6400.


I don't know for this specific laptop, but some laptops have a light sensor that can be used to automatically adjust brightness.

The loop effect can comes from a bad configuration of the electrical network frequency which induce a resonance frequency.

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  • Hmmm, I keep my light sensor switched off in my Latitude; however, the brightness arbitrarily changes sometimes. Keeping the light sensor switched on makes the brightness change in accordance with ambient lighting. – Shumon Saha Jan 1 '12 at 16:51

Some DELL laptops actually have this as a hardware issue (could it be called a 'fault' as it's not really faulty - its just that we are trying to fit non-standard parts).

Some combinations of screen and inverter board won't ever allow full brightness. The only way I have found, is to go through different screens until a compatible model is found, but its very few will work - I have about 30 screens in stock, and still couldn't find one compatible last time.

It can't be fixed by using the BIOS, or any other software either, no mater what is tried no software can alter the wrong power being sent to the inverter.

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Thats called adaptive brightness feature on your laptop. It keeps changing the effects according to how much brightness is absorbed by the screen at that point. If you want to test it, take a torch and show light on your laptop screen and the brightness of your laptop increases automatically.

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