I have a over the stove microwave it started out that everything would work but wouldn't heat anything up. how you get a buzz & the fuse blows. so far the transformer, HV capacitor, diode & mag tube was replaced & still have the same out come.

TMac, August 2009

Hi TMac,

It sounds like you've already replaced everything that could cause fuse blowing!

Is it possible that one of the replacement parts was faulty?

I guess you've had a good look at the wires and any other parts of that circuit that haven't been replaced?

I think you'll have to diagnose the problem by trial and error, by UNPLUGGING the microwave, disconnecting parts of the high-voltage circuit, then replugging and testing to see whether the overload remains. This is potentially very dangerous, since the voltages and currents are pretty much exactly in the right range to cause instant death if you do something careless!

I refer you to Sam Goldwasser's FAQ on microwave repair at http://www.repairfaq.org/sam/micfaq.htm for the details.

Be extremely careful when working in the high-voltage areas of a microwave. Don't use a normal multimeter to measure the voltages - they can't handle it and will lose their smoke. Don't touch anything (even through a normal thickness of insulation) with the microwave running. Good luck with staying alive!

Kris Heidenstrom - kris at heidenstrom dot gen dot nz, August 2009