VGA monitor not detected on iMac (Mountain Lion) but works on MBA (Lion)

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VGA monitor not detected on iMac (Mountain Lion) but works on MBA (Lion)

Hi!

I have a Macbook Air running 10.7.5 and a new iMac (27") running 10.8.3. I have an old VGA monitor that I'm wanting to use as a second display. I purchased a mini-display to VGA adaptor, and it works perfectly with the MBA. However, with the iMac, the display is not detected (I tried restarting the computer, restarting while holding opt+cmd+P+R), and of course selecting "detect displays" from the display preferences pane.

Doe anyone know: Is it a hardware issue with the iMac? Is it a software issue with 10.8.3? Those are the only two differences, as I believe that on each it's a Thunderbolt port.

I'm a bit stumped here. I've been searching for over an hour on boards and can't seem to find anyone with exactly the same problem.

-Jessi

iMac, OS X Mountain Lion (10.8.3)

Posted on Apr 5, 2013 6:02 AM

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Answer 1

Apr 5, 2013 6:08 AM in response to Jessi K

Do you have other, or access to other, devices that can be used to test the Tbolt port on the iMac? I have no problems detecting a VGA monitor or Samsung HD TV on the min-display port on a MacBook Pro running 10.8.3. Have not tried with my iMac but may just do so this weekend to find out how that detects a monitor.

Did you try in System Preferences > Displays changing whether you are mirroring on and off to see what that does?

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Answer 2

Jessi K Author

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Apr 5, 2013 6:14 AM in response to Ralph Landry1

Unfortunately I don't have any other Thunderbolt devices (unless I move the iMac into the living room and try plugging it into the TV using the mini-display to HDMI adaptor, which I may try later tonight).

I tried turning mirroring on and off; I tried setting the display resolution lower (with and without mirroring) and trying "detect displays" again. No dice. Unplugging and plugging back in the monitor; switching it on and off. Tried both TB ports. Every possible thing I could think of.

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Answer 3

Apr 5, 2013 6:26 AM in response to Jessi K

The iMac 27 is a big unit to be moving around but it looks like you need to test those ports. According to the Thunderbolt FAQ you should be able to use two external displays and interface with VGA.

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