iMac thunderbolt target display mode stopped working

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iMac thunderbolt target display mode stopped working

Hi all,

I have connected my 2012 MacBook Air to my later 2012 iMac via Thunderbolt cable. I am then using target display mode to use my iMac as an external screen for the Air.

This has worked without problem until now. Now, when I press CMD + F2 on my iMac, the screen on the iMac goes black (the Macbook Air screen is not shown on the iMac). However it appears as far as the Air is concerned, the iMac screen is functioning correctly (i.e the 'Displays' preference panel implies everything is working).

I have rebooted/reset SMC/reset PRAM on both the iMac and the Air, but with no luck.

Any suggestions?

Many thanks

Peter

iMac (27-inch, Late 2012), OS X Mountain Lion (10.8.4)

Posted on Jun 20, 2013 1:12 PM

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Answer 1

Jun 21, 2013 4:15 AM in response to petbo2

I have exactly the same problem with my Nov 2011 MBA and my 2 month old 27" imac over thunderbolt, it has never worked. Like you the MBA sees the imac properties and if you arrange the screens so they are not mirroring the mouse moves off to the other screen but the imac screen stays black.

I use Target disk mode now which works well if you want everything on the imac screen.

Marc

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Answer 2

Aug 2, 2013 1:07 PM in response to petbo2

Unplugging the digital audio cable from the back of the iMac solved it for me.

Do you guys happen to use the optical audio out too?

-- Richard

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Answer 3

QBizzy

Level 1

4 points

Dec 2, 2013 2:50 AM in response to richard_vd

Yes, That worked for me.

I was not able to get my new iMac to connect to my rMBP.

I unplugged the digital (optical) audio cable and viola - it worked. Thanks!

QB

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Answer 4

cameronw

Level 1

26 points

May 12, 2014 10:51 AM in response to QBizzy

Hi guys -

I have a similar problem. Macbook pro hooked to iMac via miniDisplay cable - it was working fine for weeks (the macbook Pro's desktop was displayed on the iMac.

Now however, when I plug in the display cable to both macs, the iMac screen goes black for a bit, and then reverts back to its original state.

Tried resetting the SMC and the PRAM on both boxes...

Any help out there?

thanks people

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Answer 5

QBizzy

Level 1

4 points

May 12, 2014 11:03 AM in response to cameronw

I found that target display mode for me, doesn't work if I have an optical/audio out plug inserted. I listen to music while I work. And I found that when I have the optical cable plugged, TDM never worked. Works fine after I unplug it.

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Answer 6

cameronw

Level 1

26 points

May 12, 2014 11:08 AM in response to QBizzy

thanks - yes, I read your post above before posting mine. I should have said I don't have any other cables, audio or otherwise, plugged into either macintosh....

So that trick doesn't work for me. This seems like a Hardware bug of some sort....

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Answer 7

mdahman

Level 1

13 points

May 29, 2015 7:58 PM in response to cameronw

I have a 27" Late 2009 iMac running 10.9.5 (13F1077) and have been using target display mode for years. At some point in the last month it has stopped working. The iMac screen goes black and then the iMac screen comes back on. In the console there is an error message: com.apple.launchd[1]: (com.apple.dpd[53]) Exited with code: 75

If I hit CMD-F2 the screen will stay black (another dpd exited error message will be logged) and the connect computer will think it is connected to another display.

I have reset the SMC, doesn't help.

I have no optical cables plugged into the imac.

I have no idea how to troubleshoot this further.

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