MacBook Pro Target Display to iMac - Black Screen

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MacBook Pro Target Display to iMac - Black Screen

I have a MacBook Pro (13'', Early 2011) & iMac (21.5", Mid 2011) using a Thunderbolt Cable to Target Display. Everything was working find and I could Command F2 to Target Display as expected.

However, about a week about this stopped working. Now when I try to Target Display the iMac goes to a Black screen (like it's switching to Target Display) and the MacBook Pro does nothing. The iMac will be at the Black screen until I Command F2 again (or disconnect the Thunderbolt Cable), then the iMac goes back to the normal display.

I have tried another Thunderbolt cable with no luck. I have perform all software updates on both machines (now both running 10.7.3) and fixed Disk Permissions.

I have also found that restarting my MacBook Pro allows this to function as excepected (Command F2, Blue Flashing Screen, Target Display on the iMac). However, this is not an ideal situation since having to restart my computer is time consuming.

Any suggestions would be appriciated.

Posted on Apr 26, 2012 6:58 AM

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Answer 1

a brody

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Apr 27, 2012 5:28 AM in response to kjosra

Could this have anything to do with it? http://support.apple.com/kb/TS3775

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Answer 2

kjosra Author

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Apr 27, 2012 5:33 AM in response to a brody

Unfortunatly no. I am using a Thunderbolt to Thunderbolt cable (I've actually tried a few different ones). And it does work after a restart of the MacBook Pro.

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Answer 3

a brody

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Apr 27, 2012 5:39 AM in response to kjosra

Is the MacBook Pro plugged in the wall?

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Answer 4

kjosra Author

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Apr 27, 2012 6:00 AM in response to a brody

Yes - usually when I get into work I hook it up to power, connect the Thunderbolt cable and then try to Target Display.

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Answer 5

a brody

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Apr 27, 2012 6:08 AM in response to kjosra

Sounds like a flaky cable to me. If changing cables doesn't work, then something is wrong with your Thunderbolt port that needs looking into by Apple.

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Answer 6

kjosra Author

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Apr 27, 2012 12:19 PM in response to a brody

I honestly don't think it's a hardware issues since it does work after a Reboot of the MacBook Pro. Something must happen when the hard disks on my computer go to sleep. I put my laptop to sleep and close it at the end of the day and take it home. When I come back in the morning I wake up my laptop and try to Target Display, but I get the black screen on the iMac and no change on the MacBook.

A restart of the MacBook and Target Display works as expect (same cable as when it didn't work). I have tried multiple Thunderbolt cables.

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Answer 7

kjosra Author

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May 2, 2012 6:21 AM in response to kjosra

Hello all -

I've done some additional testing. I tried an completely different iMac (and Thunderbolt cable) this morning and saw the exact same behavior so it is definitly something specific to the MacBook Pro.

Again, a restart resolve the issue, so it appears to be related to after the computer goes into a hard sleep (cover closed), because I can leave for lunch (cover open) and the display will go to sleep and things will still work as expected.

Any thoughts/ideas woudl be appriciated.

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Answer 8

kjosra Author

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May 15, 2012 6:28 AM in response to kjosra

Found the resolution...

If you Target Display (get the Black screen on the iMac), then go into System Preferences >> Displays on the MacBook Pro and choose Detect Displays.

It takes a minute or two, but then the Target Display starts functioning again. Not sure what caused it to break in the first place (maybe an update), but that allows the Target Display to function without a reboot.

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Answer 9

Sep 5, 2013 6:31 AM in response to kjosra

If the detect displays option is not available, hold down the Option key while you are in the Display pane. The "Detect Displays" button will appear in the lower right.

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Answer 10

Airbees

Level 1

5 points

Nov 13, 2013 7:52 AM in response to kjosra

I have fix this problem on my MBP Retina Mid-2012 - iMac 27" Late-2009

1) install and start aplication gfxCardStatus 2.3 to MBP, download: http://gfx.io

2) on MBP menu bar switch to discreet card (icon i/d), dynamic switch not worked for me

3) touch Command+F2 on iMac

4) enjoy :-)

On display settings in MBP set display mode. (2 monitors/mirrored monitors)

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