My Macmini late 2012: I shut down it in the normal way at midnight and next day morning it was completely dead. Can it be a faulty power switch, a faulty power supply or a faulty logic board? Would you reccomend to tear it down, take out the power supply module and test it. While it was working the power supply module side used to heat up a bit. In fact this unit (after upgrading to MacOS Catalina) started to experience 3 faults: 1) It would abruptly close the screen and ask for the PW (on the background things are still running), 2) It would abruptly shut down and needed to power on, 3) It would take a rather long time to bring the desktop after switching on the power (some 4-5 minutes or so...)

I have a late-2012 MacMini which came with 4GB RAM + 1 TB HDD. The RAM has been upgraded to 12GB. I upgraded the MacOSX to Catalina 10.15 but seems I am having some problems with it. I now want to replace the original 1 TH HDD with a 480GB SSD (and use it as system disk) and also add a second 1TB SSD as a storage disk. And finally re-install MacOSX High Sierra or the later OSX and get rid of Catalina. What would be your advice to place which SSD into which bay? Thank you!