I just threw out a 1977 Magic Chef with a huge interior and electronic controls that worked wonderfully until I heated some hamburgers I didn't realize were wrapped in foil. The small fire melted the inner ceiling piece and the shaft for the stirrer, and I tried for a few years to find parts to at least fix the stirrer (the inner ceiling piece was ugly but usable). Failing that, I finally gave up and made the wife happy.
It was MUCH better than any of the other microwave ovens we've had since, in that it did fractional heating (10-90%) by turning the magnetron in tenths of a second, i.e. 40% heat was on 0.4 seconds, off 0.6 seconds. This tended to heat things MUCH more nicely. The ones we've had since tend to do garbage stuff, e.g. 40 seconds at 50% heat means it heats for 20 seconds and runs the timer with heat off for 20 seconds. If I wanted to heat stuff that way I could do that myself with a bang-bang on-off controller and my kitchen clock.