My Mac Mini blinks black screen on my main monitor over and over until I unplug my HDTV from the HDMI out on the mini. Almost like it keeps losing the signal of the TV? I have tried everything from PRAM reset, to a different HDMI cable, to using the thunderbolt to HDMI adapter. I am lost and it is super frustrating. I have a 2014 mini, 60" Sony KDL60W630B/2 from HDMI, my main monitor is Dell monitor (black screens). Any ideas?