I have a mac mini 2018 model that runs mojave with an external monitor connected via hdmi output of mac mini. After login with my credentials and when the progress bar is loading my monitor turns off for about 2 seconds and then it turns on again.

Do you have any ideas about what could be happened?

  • 1
    A few questions: (1) After the 2 secs is up, does the display work fine? (2) Are you using an Apple branded HDMI cable or another one? (3) What is the model of external display you're using? (4) Does the screen resolution change (i.e. is it different after the 2 sec break to what it was before)? (5) What, if anything, have you already tried to resolve this issue?
    – Monomeeth
    Aug 29, 2019 at 9:09
  • Can you please detail it better about the "after login.. the progress bar" part? Is your system using FileVault?
    – Prado
    Aug 29, 2019 at 11:24
  • Do you notice changes in the screen resolution before and after the powering off of the screen? Could you reproduce the behavior with other screens?
    – trolologuy
    Aug 29, 2019 at 18:37
  • @Monomeeth I 'm using the bundled hdmi cable that comes with my monitor Lenovo Thinkvision LEN S22e-19. After the 2 second the display works fine! I cannot see with eyes any change in screen resolution after the break but I cannot guarantee that it does not change.
    – user28058
    Aug 30, 2019 at 4:37
  • @Prado Yew I'm using Filevault.
    – user28058
    Aug 30, 2019 at 4:41

1 Answer 1


This is standard behaviour with the built-in HDMI port of the Mini 2018 - the governing circuitry has a 'security interlock' controlled by the T2 chip, and it gets toggled when the machine moves from the PREBOOT OS (which is where your main login window actually lives) over to the standard install.

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