Second display not recognised by iMac

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Second display not recognised by iMac

My 2011 27" iMac running 10.9.2 is refusing to recognise my projector when connected to either Thunderbolt port via a Mini Displayport to female HDMI adapter and HDMI cable.

My friend's 2010 Macbook Pro (also running 10.9.2) has no such problem when the projector is connected to its Mini Displayport using the same adapter and cable.

Clicking Detect Displays on the iMac does absolutely nothing. I've tried the adapter (firmly seated) in both Thunderbolt ports. I've also tried plugging it in before and after booting and/or restarting both the iMac and the projector. I've also reset PRAM/NVRAM and repaired permissions.

Could the adapter be somehow fully compatible with the MBP yet incompatible with the iMac?

Any advice much appreciated,

Sandy

😮

iMac (27-inch Mid 2011), OS X Mavericks (10.9.2)

Posted on Apr 11, 2014 8:12 AM

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Answer 1

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badubi Author

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Apr 12, 2014 8:28 AM in response to badubi

Still no joy but some more evidence:

1 - System Information on the iMac says "No device connected" for both Thunderbolt ports regardless of whether the adapter is plugged in.

2 - Using another friend's Marshall HDMI monitor instead of the projector results in the same behaviour so the HDMI output device would appear to be irrelevant.

Below are the adapter's specs. Is there anything that would suggest incompatibility with TB?

1. The mini DisplayPort to HDMI Adapter lets you connect a high definition monitor, projector, or LCD that uses a HDMI connector or cable to a MacBook, MacBook Pro, or MacBook Air with a mini DisplayPort

2. Mini DisplayPort 1.1a input and HDMI 1.3b output.

3. HDMI highest video resolution 1080p.

4. HDMI225 MHz / 2.25 Gbps per channel (6.75Gbps all channel) bandwidth.

5. HDMI 12 bit per channel (36 bit all channel) deep color.

6. Powered by Mini DisplayPort source

7. Connectors: Mini DisplayPort Male to HDMI Female

Sandy

😐

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Answer 2

badubi Author

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Apr 16, 2014 4:23 AM in response to badubi

The new "Thunderbolt-compatible" HDMI adapter arrived today and... no joy. Detect Devices still does nothing.

So I appear unable to use a second display with my iMac via Thunderbolt and HDMI. And, since the iMac has no alternative means of connecting a second display, I would appear unable to use a second display at all.

Can anyone offer any advice at all?

Sandy

😟

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Answer 3

badubi Author

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Apr 16, 2014 9:45 AM in response to badubi

SMC reset, problem solved.

http://support.apple.com/kb/ht3964

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Answer 4

badubi Author

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Apr 16, 2014 10:29 AM in response to badubi

Sadly, I spoke (and marked this thread as solved) too soon. It worked once after my first SMC reset but has now stopped working, even after further SMC resets!

I have reported to Apple and hope it is fixed in 10.9.3.

Sandy

😢

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Answer 5

badubi Author

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May 23, 2014 4:44 PM in response to badubi

I have now updated to 10.9.3 and nothing has changed - the MBP sees the projector fine and the iMac won't recognise it despite restarts, SMC reset etc.

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