Pixelated fonts in Mavericks

Hi all

Suddenly after awaking my old Mac Mini (2014), many fonts were heavily pixelated, especially in the menus, the dialog boxes, the modal windows and in general the Finder stuff. I had made no change in my configuration: no soft install or removal, etc.

Within applications, some have no issues, some do and some have issues with certain stuff and not with others.

Images and photos are OK.

I shut down the Mac and restarted it since to no avail.

The monitor has a DisplayPort connection. I connected it with HDMI. It's the same, only bigger.

Everything has worked fine since it's in service.

Any clue about where it comes from and how to remedy it?

If it's corrupt font files should I replace the fonts in the Library? How to do it?

TIA for you advice folks.

Nick

My configuration is:

Mac OS 10.9.5

Mini 2014

AOC monitor