Repairing Microwave Ovens
Microwave engineers are highly skilled and have test equipment. It is also very dangerous inside them, lethal heart stopping voltage, dangerous radiation that can blind you in 6 seconds, plus the Magnetron core is a toxic heavy metal. An average home microwave transformer has two secondary windings. The low-voltage winding provides around 3.2 volts, but the problem is the high voltage winding provides between 1,800 and 2,800 volts (average is about 2,200 volts). The low voltage output is used to light the filament in the microwave-generating vacuum tube (the Magnetron). The high voltage AC output from the transformer is changed to DC and doubled using a voltage doubling circuit (Diode and High Voltage Capacitor) to power the Magnetron. The microwave oven transformer and voltage doubler operate at lethal voltage and current levels which will easily jump an inch of you get close to it! The capacitor has to be discharged, which is dangerous in itself. Don't mess with them unless you know exactly what you are doing which most people here on Fixya don't have the knowledge or the abilities..
There are are only three parts to a microwave, the step up transformer, the HUGE capacitor, and a magnetron. Plus control boards to run them. The test equipment and knowledge diagnoses and provides the fix. The best idea is to take it in for repair. It is not the answer you want, but the best one. It is the same with televisions, we see people here change every board and still not have a working set. The same is likely to happen to you with home microwave oven repair.