Sierra/External monitor via DisplayPort/"No signal" after sleep

Discussion in 'macOS Sierra (10.12)' started by krapidler, Oct 29, 2016.

  1. krapidler macrumors newbie

    Dec 9, 2009
    Since installing MacOS Sierra, I've had major issues with my external monitor (ACER G227HU), which is connected via MiniDisplayPort-to-DisplayPort cable (no dongle) to my early 2011 13" MacBook Pro (which is itself in clamshell mode).

    Basically every time after going to sleep, the monitor wakes up together with the computer, meaning that the little light next to the monitor's power key turns blue, but then there is never any image, and after a few seconds the monitor just displays "NO SIGNAL".

    Sometimes I can get the monitor to work again by unplugging and replugging the cable, sometimes only after opening the MBP (which is a pain because it sits vertically in a stand 1 meter away), and sometimes I actually need to restart the computer.

    Something else I've noticed is that DURING sleep, the monitor sometimes goes from being completely black (no backlight) to black backlight, displaying "NO SIGNAL" for a few seconds until it goes back to sleep.

    What I've tried so far:
    • install 10.12.1
    • use another (newly bought) MiniDisplayPort to DisplayPort cable
    • adjust "energy" times in system preferences so there is no conflict between screensaver, display off and computer off
    • reset NVRAM
    • reset SMC
    • used an HDMI cable instead - this seems to work, but then the Acer monitor won't work in the monitor's default resolution (2560*1440) because HDMI doesn't seem to be able to go that high
    Would anyone know what this could be/how to fix it? Happy to upload logs, just let me know what you need exactly and how to find them ;-)

  2. Julien macrumors G4


    Jun 30, 2007
    I have what may be the same issue on a Mac mini. Here is my post:

    Have a Late 2012 mini with a ViewSonic VP2770 DisplayPort hooked to the Thunderbolt/Display port and works great until…… I have Screen Saver set to come on in 2 minutes and Display Sleep in 1 hour. I also have a spare Asus 1080 HDMI monitor and this is when the problem begins.

    …..When I hook up the Asus 1080 to HDMI all is fine and I have them setup as Extended. When the Screen Saver starts all is fine. However in about 15 to 20 minutes my ViewSonic (TB/DP) seems to go to sleep (ahead of time and Screen Saver running on HDMI). I can’t wake it up. It seems more like the Thunderbolt /Display port has gone dead. I have to restart my mini to get the Thunderbolt/Display port to power on my ViewSonic.
  3. deesto macrumors newbie

    Mar 3, 2013
    I've had something similar happen on my late-model 2013 MacBook Pro 15': I updated OS X on Friday with the latest updates available -- I was already on 10.12.1; Friday's updates included Xcode, iTunes, and office apps. I left it running over the weekend after the updates, but didn't log in, which I just did now. Everything seemed fine on log in, and I rebooted, which is when my external monitor completely stopped working. I tried powering the display on/off, pulling the HDMI cord, moving to different HDMI ports, and nothing worked. I rebooted the MacBook Pro again, and instead of rebooting, it shut down. I turned it on again, and when it booted, the display was there as if nothing had happened. Seems flaky and a bit worrisome that it will happen again.
  4. SteveWilhelm macrumors newbie


    May 8, 2017
    I am having a similar issue with my Mac Mini 2012 2.3 GH Intel Core i7 running MacOS Sierra with a Dell U2717D connected to the mini DP to DP port. I also have a Dell P1215Q connected via the HDMI cable.

    When I leave for long periods of time, I turn off both monitors, but leave the Mac Mini running.

    When I return, the P1215Q responds immediately, but the U271D displays 'Scanning for signal' on the DP port.
  5. bernie-uk macrumors newbie

    Jan 10, 2012
    I've noticed a similar issue with my Mac Mini (Late 2012) running macOS Sierra 10.12.5
    Nearly every time the machine sleeps, the monitor (Asus PB287Q) connected to the Displayport does not come back.
    The HDMI output is fine, and sometimes corrects itself with a reboot. The DP on the monitor works fine for other machines.

    I tried an SMC Reset and that did not help.

    One possible fix that has been working the last few days is to turn OFF "Put had disks to sleep when possible" in the Energy Saver panel in System Preferences. Hopefully it is just a software issue and will be fixed in the future.
  6. kozmic macrumors newbie

    Nov 8, 2016
    Well I can confirm that this issue still exists in High Sierra as well... closed lid / clamshell mode, in vertical stand, with external monitor connected via HDMI port works fine 100% of the time.

    If monitor is connected via thunderbolt/mini displayport, and macbook pro (early 2015) goes into sleep (or I try to reboot), the external monitor initially appears to receive signal and the monitor itself wakes, but then never receives display signal from macbook pro. At which point, I must remove the macbook pro from the the dock, and open the lid (sometimes having to force shutdown/restart, by holding the power button down).

    There is definitely a bug related to thunderbolt / mini displayport waking from sleep.

    Interestingly, upon waking the macbook pro, my external ATTO 10Gbs NIC box connects and works just fine connected to another thunderbolt port. So the bug must be related to the thunderbolt port as a display port...

    Very annoying!

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