How can I fix my Sharp R-408DW (s/n 181107) 1200 Watt microwave?

It was completely dead so I replaced the ceramic fuse. I plugged it in to my bench outlet and it ran for a few seconds and then it popped the breaker in my bench outlet. I tried it again and the same thing happened. The microwave hums (not sure if it's the right hum) and the fan turns but not for long. Not sure whether I'm having a problem with the power supply, microwave generator, or turntable motor. The unit was purchased 01-08-01. What goes bad in these units after only six years? Currently have the unit completely disassembled. Have a Fluke meter handy but don't have any spec numbers to test against. Thanks.