I don't really feel up to "walking you through a testing regimen", but maybe in the Zen sense I can show you the path, and you can walk the path yourself. In addition to the fuse, there are other switch-like elements, all in series, which may fail. Sometimes there is a thermostat, or thermal fuse, to make sure the oven cavity doesn't get too hot. Always there are interlock switches, to make sure the door is closed before energizing the microwave generating circuits. Often times there will be printed circuit diagram, printed on paper, pasted to one of the inside surfaces of the metal cover. This can be helpful. There are also resources like this one:http://www.repairfaq.org/sam/micfaq.htm Keep in mind while working that you do not want to touching the insides of your microwave while there is the possibility of these circuits becoming energized. This suggests that you should do your poking around, disconnecting, reconnecting, etc, while the oven is UNPLUGGED. The repair FAQ linked above has some other safety tips, e.g. for discharging the HV capacitor, etc. In fact it might be prudent to read that guide first.