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OS X - Operating System General OS operation information and support

iMac Black Screen


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maurimar

 
Member Since: Nov 05, 2011
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I upgraded my iMac 20" today to Lion. Everything worked well. Then this evening the display went black. I rebooted and no difference. I can hear the computer work but the display remains black. I reset the PRAM: no difference.
Help please.
Mauri
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chscag

 
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Do you have another monitor or TV you can hook up to your iMac to see if it works from the external display? Let us know.
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maurimar

 
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I got it to work after resetting the PRAM. I believe it is an issue that Lion has with the Mozilla settings, as I learned from other forums.

now the screen is back on but there is noticeable flicker when the CPU is working. I doubt this is a hardware problem as it happened right after installing Lion and after the black screen. Any thoughts?

Thanks.

Mauri

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Originally Posted by chscag View Post
Do you have another monitor or TV you can hook up to your iMac to see if it works from the external display? Let us know.
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chscag

 
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Quote:
I got it to work after resetting the PRAM. I believe it is an issue that Lion has with the Mozilla settings, as I learned from other forums.
What Mozilla settings are you referring to? Are you using Firefox as your browser per chance? You can always switch back to Safari to see if the same flicker occurs. Flicker is usually caused by an improper refresh rate for your monitor. Go into your display settings in System Preferences and make sure they're set to reflect the native resolution of your iMac display.
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maurimar

 
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I claimed victory too early.... the iMac has gone black again. Same problem: I start it up, I can hear it's working, but the screen is black.
Could it be a hardware problem? But the coincidence that this happened right after installing Lion makes me suspicious.
Help please.
Mauri



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Originally Posted by chscag View Post
What Mozilla settings are you referring to? Are you using Firefox as your browser per chance? You can always switch back to Safari to see if the same flicker occurs. Flicker is usually caused by an improper refresh rate for your monitor. Go into your display settings in System Preferences and make sure they're set to reflect the native resolution of your iMac display.
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chscag

 
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Go back to my original reply to you and hook an external monitor or TV to the iMac. That's the only way we're going to find out if the problem is hardware related with your iMac or if it's something else. Let us know and we can go from there.
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Imagesinspace

 
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Connecting a second monitor worked for me. It allowed me to shut down the Mac using the shutdown command under the apple menu. When I restarted the iMac the monitor came back to life.
This doesn't solve the problem of a perpetually sleeping screen but gets you out of it so you can keep working.
BTW my monitor stayed black even after a forced restart (holding down the start button until it restarts). The Mac must be remembering the settings for a sleeping screen and start up with this in place.
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fazed

 
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Hello,

I have the same problem, but it isn't a Lion problem cause I've always been with snow leopard in my Imac 27". Yesterday everything worked fine in my computer, and this morning when i turned it on, the screen stays black. I know the computer is running because i can hear it, and if i press the play button in the keyboard i can get itunes to play. I tried connecting an external monitor and it works, but because its not the principal one i can't get the preferences window to open or any window to open.

I also tried disconnecting the computers for a while, or booting it up holding cmd+opt+p+r, but nothing worked.

Anyone has any idea of whats is the problem or the solution?


Didz
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chscag

 
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If an external monitor works OK, it has to be something related to the iMac display that's not working properly. First, make sure that the display is not sleeping all the time by resetting the System Management Controller.

Do this: Remove the external monitor. Shut the iMac down completely, remove the AC cord from the outlet. Let the machine stay off for at least 10 minutes. Plug it back in and turn it on. Let us know.
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