iMac not working as external display

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Level 1

60 points

iMac not working as external display

I have a Macbook Pro and a late 2013 27" iMac, both with Mini Display ports and both running OS X Yosemite 10.10.3. I've connected both of them using a brand new Apple-brand Thunderbolt cable, as per Apple's instructions. You're supposed to be able to press Command F2 on the iMac to put it into Target Display Mode. But when I press Command F2 nothing happens. At all. Every function key works. Both computers work. All keys work. F2 works as a function key (brightness). But the Target Display Mode isn't working. Any ideas what I can try to fix this?

Posted on May 6, 2015 11:58 AM

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Answer 1

rkaufmann87

Level 10

140,532 points

May 6, 2015 12:38 PM in response to Adwiz

Unless the MBP also has a Thunderbolt port (note this is the same size as a mini display port) TDM will not work. Have you verified your MBP has Thunderbolt??

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Answer 2

Adwiz Author

Level 1

60 points

May 6, 2015 12:48 PM in response to rkaufmann87

Yes, I wouldn't be able to plug the cable into both devices if it didn't :-)

I also checked the MBP Thunderbolt port and both on the iMac with an external projector to make sure they are both working. I wonder if the cable could be the problem but that would be unusual for a brand new cable. Still, I suppose it's possible. Unfortunately, I don't have any devices that have the female Display port so I can't check the cable to make sure it's okay. I was wondering first if there might be a known issue.

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Answer 3

rkaufmann87

Level 10

140,532 points

May 6, 2015 12:54 PM in response to Adwiz

As I mentioned a Mini Display port is identical in size to a Thunderbolt cable, that I why I asked you to verify that your MBP has a Thunderbolt connection. Exactly which MBP do you have?? Please cite the year and model.

You may have 90 days of free AppleCare support, I'd suggest you contact them. I don't know what country you are in so I'd suggest using Contact Apple for support and service - Apple Support to find the correct phone number for your area.

Also use Apple's TDM FAQ, you can Google for that.

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Answer 4

Adwiz Author

Level 1

60 points

May 6, 2015 9:20 PM in response to rkaufmann87

My MacBook Pro is a late 2011 model and the 27" iMac is a late 2013 model. The MBP just has a Mini DisplayPort rather than a Thunderbolt port. I think I discovered the problem. Further investigation revealed that I can't always use a Thunderbolt cable because even though it looks the same as a Mini DisplayPort cable and fits and even though the Mini DisplayPort has a Thunderbolt icon next to it, the cable won't support the same functionality on devices as old as 2011. So I've ordered a Mini DisplayPort to Mini DisplayPort cable. Apple doesn't make them. I had to get a third-party cable. But from what I've read it should work fine with my devices.

I appreciate your help trying to find the issue.

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Answer 5

rkaufmann87

Level 10

140,532 points

May 6, 2015 9:41 PM in response to Adwiz

Good luck.

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