Well, I got a fuse, put it in, and the panel came alive with the clock and controls working.
I put a glass of water in it, and turned it on. The wires that come out of the capacitor in the power supply bundle caught on fire. The fuse did not engage, or the wire size was too small, and it didn't reach 20 amps.
Upon looking at the power supply bundle, I noticed that several wires had been cobbled together with wing nuts and electrician's tape, definitely not a factory fresh application. The transformer had been either moved, or replaced, and the holes in the frame were not into the original base of the transformer, hence I think it is not the original transformer. The wires are combinations of two wires of different colors.
SIL says that "It just quit working one day." From what I see, it was worked on, things were altered, and things were altered badly. I shall try to get an honest answer, but you know how that goes.
The control panel controls the microwave and oven. We may have to just take off the microwave, and leave the control panel, and just settle for using the oven, and put a different microwave in the available space, using the keypad on the new MW.
I need to find a capable electronics guy in our small burg who can come and find out just what's wrong. Good luck. I have put it on craigslist, and the local repair services want $100 to show up. I may bite the bullet, and do that if I can't find anyone for less.
Will keep you posted.