Plugging in an external monitor and it doesn't work

Discussion in 'Mac Apps and Mac App Store' started by Forkjulle, Feb 18, 2013.

  1. Forkjulle
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    macrumors regular

    Aug 1, 2012
    I have a Macbook Pro (retina) and, using a HDMI cable, I plugged it into a Dell U2711. Mountain Lion suddenly changes the screen display on the Macbook, but nothing happens on the Dell. It's just a black screen that says nothing is connected to it.

    But clearly the Macbook sees it. When I unplug it, the screen display reverts to the original version.

    What am I doing wrong?

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