CATV Monitor won't display.
I am trying to get a friend's old Mac Mini to display the desktop or anything else on a CATV monitor. It is running High Sierra which is as high as the OS can go on this mini. Firstly it's a 2010 Mac Mini that has been attached to a Lacie CATV Monitor for years and has worked well for her. She uses it for writing only. She has been having problems with the text being very fuzzy on startup. I have change the resolution a number of times and seem to have found a sweet spot where if is left for a few minutes the fuzziness goes away. Today it was beyond fuzzy. There were duplicates of anything showing on the screen so I tried adjusting the resolution on the monitor again to 'default for display' instead of 'scaled' where it has been for years. Usually when changing the resolution the screen goes momentarily black but then comes back with the new resolution. This time the screen stayed black and I have no way to access the display settings in the system preferences. I was able to start the computer in safe mode and select guest instead of the admin to see the desktop and adjust the monitor settings back to what worked before but when I start the computer in the admin option, the screen just goes back to black. I realize that changing the screen res as a guest won't affect the settings under the admin access. Is there anyway to get the desktop to show using the admin access than anybody knows of? Thank you.