captainlarrydart
Level 1 (4 points)
Desktops

Q: iMac screen dips to black while using Safari

When using Safari on my late 2014 iMac 27", the screen will often randomly dip to black.  Tapping the space bar will revive it, but it will sometimes immediately do the same thing again.  When it does exhibit this behavior, the Console message is:

 

8:50:52.295 AM WindowServer[185]: device_generate_lock_screen_screenshot: authw 0x0(0)[inf, inf, 0, 0] shield 0x7f9be085d600(2001), dev [2048,1152]


This is the second machine that this happens on, the first was a late 2009 27" iMac.  It does not happen on my laptop. The system is:


iMac (Retina 5K, 27-inch, Late 2014)

3.5 GHz Intel Core i5

32 GB 1600 MHz DDR3

AMD Radeon R9 M290X 2048 MB


Any help you can offer with this deeply frustrating problem is gratefully appreciated.

Posted on Apr 12, 2016 6:06 AM

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captainlarrydart

Q: iMac screen dips to black while using Safari

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  • Helpful answers

  • by alex_h1,Helpful

    alex_h1 alex_h1 Apr 13, 2016 3:01 PM in response to captainlarrydart
    Community Specialists
    Apr 13, 2016 3:01 PM in response to captainlarrydart

    Hello captainlarrydart,

    Thanks for using Apple Support Communities.

     

    I understand from your post that your Mac is seemingly going to sleep on its own, sometimes immediately after waking up.  To help troubleshoot this issue please follow through all of the steps outlined below.

     

    If your Mac goes to sleep unexpectedly

    Make sure that Energy Saver is set up the way you want: choose Apple menu > System Preferences, then click Energy Saver. Adjust one or more of the following controls to affect when your Mac goes to sleep. Some of these controls aren't available on your Mac model.

    • "Turn display off after" slider
    • "Display sleep" slider
    • "Computer sleep" slider
      If a slider is set to "Never," sleep is disabled for that feature.
    • Schedule button

    Make sure that you aren't putting your Mac to sleep accidentally:

    • Pressing the power button can put your Mac to sleep.
    • Moving your mouse pointer to a hot corner can put your Mac to sleep, depending on your Mission Control settings. Choose Apple menu > System Preferences, then click Mission Control. Click the Hot Corners button, then see if any of the corners are set to "Put Display to Sleep."
    • Using magnets near your Mac notebook can put your Mac to sleep.

    If the previous steps don't work

    These additional steps may help identify or resolve the issue: 

    • Reset the SMC.
    • Reset NVRAM.
    • Disconnect external devices other than your Apple keyboard, mouse, and display. If that resolves the issue, gradually reconnect your devices, testing each time, until you find the device that is interfering with sleep. Then check the documentation that came with the device, or contact the device manufacturer.
    • Start up in Safe Mode to see if the issue is related to non-Apple startup items, login items, or kernel extensions. 
    • Try to isolate the issue by using another user account. 

    If your Mac doesn‘t sleep or wake when expected

     

    Have a good one.