908      iPhone_iPad_Mac_apple

Top Half of Screen Dark

This has been happening for some time. I thought it was the inverter, but maybe not. When I first start up my iMac and I see the grey screen, for a split second the whole screen is evenly bright, but then the top half dims. I noticed this starting a while back when my screen would dim after inactivity and the top half would flicker and make a buzzing sound, but that issue went away. Now the top half is more dim than the lower half all the time, even as I adjust brightness - the top half dims along with the bottom half, but is always more dim than the bottom half. If I adjust brightness down from full I hear a very faint buzzing sound.

Is this a hardware issue?

This is a 2008 iMac 20"

Safe Boot, (holding Shift key down at bootup), is the top still dark?

Shine a flashlight at an angle & move it around at different angles to see if if you can see a dim Desktop on the dark part.

The subject title to my thread is misleading. The top half of my screen is not dark. It is more dim than the lower half. Upon startup when the grey screen appears, for a split second everything is evenly bright, then the top half dims slightly. I can still see the screen just fine. As I adjust the brightness, the top half parallels the brightness of the bottom half, just more dim than the bottom half. Does this make sense? This has to be a setting issue since I see even brightness for a short time in the grey screen at startup. Any ideas?

Is the brightness equal in Safe Mode?

No. The brightness is still unequal in safe mode. Any ideas?

Perform an Apple Hardware Test.  It might not find anything but it would still be woth running.

Intel-based Macs: Using Apple Hardware Test

I can't get AHT to work. I'm using the lastest version of Lion. I recently reinstalled Lion from a USB drive I created before reinstalling. I tried holding down D, Option-D, and D using the USB drive. No dice.

I read on that link that for Lion the AHT is online, though how that works I have no idea. I am on 10.6.

Do you still have a clone of your 10.5 or 10.6 OS, because if you did you could boot into your clone and use the relevant DVD to test your hardware when booted into that same hardware environment.

I have this EXACT problem. The only way I've found to cope is to sleep/wake the display repeatedly until the top half stays at its original brightness. I would like to find a less insane solution.

It sounds like the backlight is failing.

Is there a way to fix this without disassembling the entire display?

Doubtful , it may require a new LCD panel. 

Pity. Thanks for the information!

It's pass a lot of time, but I found this post and I have the exactly problem. Did someone figured out with this?

Thanks

Mine was doing the same exact thing. There are 4 white plugs under the LCD on the right side. One of the plugs in the top corner on the right was partially unplugged. Pushed it back together, put the display to sleep, woke it back up and the screen Was fine again.

最後更新：2017-09-02 03:06:09

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