3 Replies Latest reply: Oct 11, 2013 1:22 PM by kabaker
kabaker Level 1 (0 points)

Second display is a 24 inch Cinema LED display. I have tried restarting & zapping PRAM, but the flashing continues. After about 5 minutes it appears stable again but I don't know why. This has happened before, many months ago, and similarly stabilized until now. Thanks.

MacBook Pro, Mac OS X (10.7.5)
  • sterling r Community Specialists

    Hello kabaker,


    Here is an article about troubleshooting external displays with your Macbook Pro named Apple computers: Troubleshooting issues with video on internal or external displays found here http://support.apple.com/kb/ht1573.



    Check connections

    When using an external display be sure to check the following:

    1. If you're using an Apple notebook, confirm the AC power cable or adapter is securely connected to the computer and the cable providing power to the display is also secure. It is always good to have your notebook connected to AC power when an external display is in use.
    2. Confirm display adapters are fully seated in their respective connections and that they are supported models and for the computer and display. Refer to these articles to assist you with adapter compatibility and further configuration information:
    3. Remove all display cable extenders, KVM switches, or other like devices and retest to determine if the issue is resolved.
    4. If more than one video adapter is in use—or "daisy-chained"—troubleshoot by using only one adapter.
      • Example: A mini DisplayPort to DVI adapter connected to a DVI to HDMI adapter is an unsupported configuration because there is a series of adapters in use.
    5. If available, try using a different display and or adapter (or use a different connector by using DVI instead of VGA, for instance).

    Reset the system
    You can reset the Mac's parameter RAM and SMC.Reset the resolutionStart by resetting the Mac's parameter RAM. If the display does not come up, was previously set to an unsupported resolution, and still results in no video:

    1. Start up in Safe Mode.
    2. From the Apple () menu, choose System Preferences.
    3. Choose Displays from the View menu to open the preferences pane.
    4. Select any resolution and refresh rate that your display supports.
    5. Restart your computer.


    I know you said you have reset the PRAM so you can skip that part if you come to it.


    All the very best,


  • kabaker Level 1 (0 points)

    Thanks, but none of this stuff makes any difference. No adapters are involved because the Cinema display has its own power, video connector and USB cable assembly. I brought the display, still under AppleCare coverage, into an Apple store where they left it running for a day and a half connected to one of their MBPs. The display didn't blink for them.


    Could it be heat-related, in my MBP's video circuitry?


    Another long-shot: Does the hard drive have a temperature-related automatic recalibration? In my older older MacBook Pro, I was getting some extraneous buzzing in the audio section when I was converting music from vinyl records to digital format. I tracked it down to audible vibrations from the hard drive recalibration. Wondering whether today's version of temperature-related drive recalibration could be behind it.




  • kabaker Level 1 (0 points)

    I seem to have fixed the problem, running several days now for long periods of time with no bliinking of the Cinema Display.


    Here's what I did:


    Carefully cleaned the contacts in the video output port of the MPB, and the connector to the Cinema Display.


    Went back to using the MPB power cord, and not the power connection from the Cinema Display. When I went back to the power connector from the display, the blinking returned.


    I have some thoughts about why I was successful, but since I'm not an electronics engineer, I'll spare you.