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I have a Cryo laptop with Windows 7 installed, bought in December 2011. Sometimes the screen seems to persistently dim and/or brighten up, even as I am doing things. In fact the brightness is varying even as I type this.

The battery is always fully charged and connected to the mains. I have checked many times the battery/power-saving settings always leaving the settings the same way; full brightness and never dimming when on the mains. Yet when the screen starts playing up I can end up with the screen dimming and brightening almost continuously.

I once went to the "adjust screen brightness" window when the screen had dimmed. I found the brightness slider on 100% (as I expected) but, as I dragged it to the left, to dim the screen, it first brightened and then started dimming, i.e. the screen setting said 100% brightness but it was only at, maybe 80%.

I have checked with Cryo and they just say check the power settings. I know what these are and how to work them and always set them to never dim/full brightness, yet still my laptop starts this dimming every so often.

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4 Answers

up vote 5 down vote accepted

It could be a hardware issue... a failing/bad screen inverter. This is a small, narrow printed circuit board mounted to the bottom of the LCD panel which inverts the DC power provided to the laptop to AC power which the Cold Cathode Fluorescent bulb requires. This of course, would depend on whether or not your laptop had an LED lit or CCFL lit screen. You only provided the make of the laptop, and not the model, so there isn't any way to determine which type of illumination is used here. But... there is a great chance that your laptop has a CCFL bulb and not LED... which would point to the inverter as being a possibility.

Now. If you have an inverter, it could be the inverter, or the power connection to the inverter, or the power connection to the bulb, or even the bulb itself (As in the case of an HP DV2000 I had to repair once, where the issue was a burnt connection at the bulb itself).

So... what do you do? First, determine if it is hardware or software. Download ANY LiveCD Operating system. You could download a Linux LiveCD (Ubuntu, Linux Mint... even Parted Magic would work), burn a disc of the OS, and boot to the disc. Once in that OS, wait and see what the deal is. Does your screen start dimming the same way it did with your install of Windows 7? You know... Unpredictably? If the issue is a hardware based problem, it will happen regardless of what OS you are using... which is the point of this diagnostic step. This would prove it wasn't a power settings issue.

If it is a hardware issue... then it gets to be a bit more dicey. Since the laptop is less than a year old, if you bought it new, it is still under warranty, and should now be sent back to the manufacturer for repair. So... you would call Cryo tech support again, tell them the new diagnostic step you just followed (booting to a LiveCD Operating System and seeing the problem repeat), inform them you strongly believe it is a hardware problem, and arrange to have it shipped back.

If it is NOT a hardware issue, meaning that the backlight works just fine and without issue no matter how long you use your LiveCD Operating System, then reinstall Windows 7 fresh, and make sure your power settings are as you want them.

It is important to note, that there is a non-screen related possibility here. Power. If your power adapter port is damaged at all (where the power cord plugs into the laptop), where any slight movement momentarily interrupts power, this would also cause the screen to dim when it went from the mains to the battery.... and then to go back to being bright again once power was restored to the mains. This could also be caused by a failing power adapter. You'd need a multi-meter to test your power adapter to see if it is putting out a constant supply of power. You can see how much wiggle room you have when you plug the power adapter into the laptop... to also see if this affects whether or not you have a constant supply of power.

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Thank you so much for this. At last something I can work on. Cryo are helpful and I have a 3 year full warranty so it is something to mention to them for their input. Trying a new OS could be difficult however since this is intermittent - how many days do I stop using the pc and what do I do with the new OS meanwhile? And, even if I go a week with no problems, I still can't be sure that it just didn't occur in that time as I can go several days (I can't say I have counted) without it arising while using Windows. Still, something to try. Thanks again. –  Rowland Mar 26 '12 at 14:02
    
The beauty of using a LiveCD based OS like Linux Mint or Parted Magic, is that you don't have to install it, or make any actual changes to your existing system to use it. You just download the ISO of it, make the CD or DVD from the ISO, and then boot to the disc. From there, it will just work without installing anything to your hard drive. Perfectly temporary. The benefit to trying Linux Mint, is that it will most likely detect and use your Wireless, so you can get online and use the computer while you wait to see if the light dims. –  Bon Gart Mar 26 '12 at 14:14
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Pay attention to what programs your using while this is happening.

I've had this problem with a brand new HP notebook with Windows 7. The computer was brand new, I looked at all the settings, everything set to 100%.

However I noticed something strange: This dimming and brightening would only occur while using Internet Explorer to surf the web. Switching to Google Chrome has fixed the problem.

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Sometimes the screen seems to persistently dim and/or brighten up, even as I am doing things. In fact the brightness is varying even as I type this.

Only sometimes? You should determine the exact circumstances.

Does it happen all the time no matter what is being displayed on the screen? For example, what if you minimize everything and leave it showing the desktop for a while; does it keep doing it or not (or does it do it for a moment then level out and stop)?

What if you watch a video? How about if you switch browser tabs from light pages to dark pages?

If it only happens when the image on screen changes from a bright image to a dark one and vice versa, then it is the power-saving features of the video-adapter.

If it happens no matter what, then it could be a hardware problem (though from what you have described, it sounds like the former).

The battery is always fully charged and connected to the mains. I have checked many times the battery/power-saving settings always leaving the settings the same way; full brightness and never dimming when on the mains. Yet when the screen starts playing up I can end up with the screen dimming and brightening almost continuously.

So it only happens when on battery? Is it a rapid changing both up and down (i.e., flickering), or a smooth transition?

A flicker sounds like a hardware issue while a smooth transition is indeed the power-savings feature at work.

I once went to the "adjust screen brightness" window when the screen had dimmed. I found the brightness slider on 100% (as I expected) but, as I dragged it to the left, to dim the screen, it first brightened and then started dimming, i.e. the screen setting said 100% brightness but it was only at, maybe 80%.

I have checked with Cryo and they just say check the power settings. I know what these are and how to work them and always set them to never dim/full brightness, yet still my laptop starts this dimming every so often.

The power-saving feature in question is not Windows’ power-saving feature, but rather, part of the video-adapter’s drivers.

You did not mention the model of laptop, but a little research shows that some of Cryo’s systems use Intel video-adapters which are notorious for this behavior. You can disable the function in the Intel Media Control Panel, but you will need to repeat it unless you disable the Intel-specific settings.

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I have a netbook that no matter what I've tried to change, will always dim while not plugged in. This lead to an incredible amount of blinking between dim and bright, which led to my discovery of a broken power jack.

Replaced the power jack and it's right as rain.

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