Um did you clean control panel with chemicals eg spray an wipe As chemicals can cause touch membrane to seperate so it doesnt make contact electrically any more The touch membrane can just fail over time as well or the connection into the circuit board can come loose

Normally most microwaves have a internal fuse on the circuit board thats sits on top of the fan This normally blows for a reason The most common 1 I remember is the lightbulb blows taking out fuse A loud bang is not a good thing it is normally a component destroying itself With a electricial short

When i used to fix these i would now pull top cover backwards enabling all acces for testing except for turntable motor

James E