senorbill2000

Q: External display flickers and snowy with El Capitan

I have an intermittent problem on a new LG Display.

LG 27" Display 27MP58 connected to Macbook Air 11' with El Capitan (10.11.4) flickers and the picture goes snowy. This happens about 10% of the time.

So in order to determine if it was the connection, the display or the computer I connected the display to a Macbook Air with Yosemite and it was very stable. This convinced me El Capitan was the culprit.

Since I am reluctant to downgrade the OS to Yosemite, Is there another fix with El Capitan for the flicker.

Thanks

Posted on May 15, 2016 7:05 PM

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Q: External display flickers and snowy with El Capitan

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  • by norm123,

    norm123 norm123 May 17, 2016 6:27 AM in response to senorbill2000
    Community Specialists
    May 17, 2016 6:27 AM in response to senorbill2000

    Hello senorbill2000,

    I understand that you are having an issue with an external display connected to your MacBook Air. You have considered reinstalling OS X Yosemite,  but would like to explore some additional troubleshooting options before going that route. I can help you out with that. 

    Anytime that you have issues with the display, I would always start with ensuring the connection between the two. Start with reseating the cable's and also checking that your Mac is up to date with it's software. Another thing to try is to reset the SMC and NVRAM. Take a look at the articles below and it will go into more details on what to do when you are having issues with your external monitor. 

    Get help with video issues on external displays connected to your Mac
    https://support.apple.com/en-us/HT201177


    Take care

  • by JimmyCMPIT,

    JimmyCMPIT JimmyCMPIT May 17, 2016 6:34 AM in response to senorbill2000
    Level 5 (7,491 points)
    Mac OS X
    May 17, 2016 6:34 AM in response to senorbill2000

    did you use the same cable or a different one?

    99 times out of 100 I fix this anomaly on the macs I support with a new cable or if none is available switching the ends of the cable, or using a different input.

    since the problem is intermittent it's often impossible to reproduce steps to make it occur but it does not appear to be related to any specific OS over another.

  • by senorbill2000,

    senorbill2000 senorbill2000 May 18, 2016 5:42 PM in response to JimmyCMPIT
    Level 1 (8 points)
    Mac OS X
    May 18, 2016 5:42 PM in response to JimmyCMPIT

    Thank you very much for the advice, but I seem to have an unusual problem. The cable works fine with another computer, so I am assuming my connections are ok..

    What is happening is the screen goes snowy for 10 to 20 seconds a few times every hour with El Capitan.

     

    I have done two different things which cure the problem and may be clues as to the cause.

     

    The first was using the display on another computer with Yosemite OS. That worked fine for over a day with no problem.

     

    The second thing was to change the resolution from 'Best for LG IPS FULLHD' to Scaled 720p.

    With 720p resolution the screen has stayed stable for a couple of days now. I just switched back to 'Best for LG IPS FULLHD' to write this reply and it has gone snowy three times already. So the resolution setting seems to affect it also.

    Another clue is the external display goes snowy but the MacBook is stable, but maybe that is obvious.

     

    I had reset the SMC, but I will try that again and NVRAM.


    Thanks again.

  • by JimmyCMPIT,Helpful

    JimmyCMPIT JimmyCMPIT May 19, 2016 11:30 AM in response to senorbill2000
    Level 5 (7,491 points)
    Mac OS X
    May 19, 2016 11:30 AM in response to senorbill2000

    it could be the video is loosing synchronization in that mode.

    long shot but from the display of the 2nd monitor open

    >System Preferences>Displays

    Hold down OPTION and click Scaled and you should see additional video resolution options. try a different resolution on the 2nd monitor.

  • by senorbill2000,

    senorbill2000 senorbill2000 May 19, 2016 6:11 AM in response to JimmyCMPIT
    Level 1 (8 points)
    Mac OS X
    May 19, 2016 6:11 AM in response to JimmyCMPIT

    I believe you are right because it does work with 720p. The other resolutions 1080, 1600X900 give the flicker and snow. Do you think this is the only solution until El Capitan gets upgraded to eliminate this bug, if that is what it is.

  • by JimmyCMPIT,Helpful

    JimmyCMPIT JimmyCMPIT May 19, 2016 2:16 PM in response to senorbill2000
    Level 5 (7,491 points)
    Mac OS X
    May 19, 2016 2:16 PM in response to senorbill2000

    I may have an opportunity to test later this week so I'm going to see if i can reproduce it on a Samsung LCD, but i think the 2011 MBA has integrated video, I have a 2012 Pro with internal video. Integrated GPU are generally inferior HW wise vs same age dedicated GPU, but if it didn't happen before it 10.11.5 with same cables, LCD and adapter could be driver related if it's not the adapter itself.

  • by senorbill2000,

    senorbill2000 senorbill2000 May 22, 2016 6:02 AM in response to JimmyCMPIT
    Level 1 (8 points)
    Mac OS X
    May 22, 2016 6:02 AM in response to JimmyCMPIT

    Another clue ... I have upgraded to 10.11.5 and the display works with the resolution setting 1080i as well as 720p. Both of these settings have a warning that they are not recommended and suggest 1080p (which unfortunately gives the flicker and snow periodically for 10 to 20 seconds).

     

    Right now it is more a curiosity to understand what is happening because I can use the display with these alternate resolutions.