I've got a 2014 Mac mini running OSX 10.11.6 connected to 2 screens; one via the native HDMI and one via a Thunderbolt to HDMI convertor.

It has been running fine for about 2 years. I turned it off around the 19/12/18 and turn it on 7/1/19.

The screen powered via the Thunderbolt to HDMI convertor works fine, and if I swap the screens around I can verify this. But for some reason, the screen plugged into the HDMI port doesn't work. I've done some multi-variable testing to test the various components and can only conclude the HDMI output on the Mac mini isn't working.

I've tried restarting the machine several times and I've tried relaunching Finder several times. But the second display connected to the HDMI port just wont work. It just shows up a black screen with a generic error "check signal". If i go the System Preferences > Display the second display isn't listed.

  • 1
    You've pretty much narrowed it down to a faulty HDMI port. There can be any number of reasons for this from a physically broken port to a failed/damaged component on the logic board. It's probably time to take it in for service. – Allan Jan 7 '19 at 22:59
  • @Allan i noticed that the mac mini 2014 has 2x thunderbolt ports, can i use both of those to power displays and not use the HDMI at all or dose 1x of the video outputs have to be via HDMI ? (Side issue is that if this dose work in principal the Belkin thunderbolt to HDMI connectors i have wont fit side by side in the mac mini as the thunderbolt ports are very close together) – sam Jan 7 '19 at 23:30
  • You should be able to use both TB ports. – Allan Jan 7 '19 at 23:34
  • @allan is there any way to do a system report from OSX that could tell me if it is a hardware issue ? – sam Jan 13 '19 at 13:00
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    You could try AHT - Apple Hardware Test. Hold D while booting from a powered off state with the AC adapter attached. Also try booting in Safe Mode to see if it's a software issue. However, hardware issues are usually easy to diagnose - it either works or it doesn't – Allan Jan 13 '19 at 13:29

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