Microwave oven noises

Lately my 20 year old microwave oven has taken to making some frightening noises: humming, buzzing, grinding, etc.

These noises seem to be emanatng from the plate turning mechanism.

Are these noises predictive of danger?

Getting a new one would be no problem, but I don’t to pitch this microwave oven if it still works and is safe.

I doubt it’s coming from the turntable. The microwave’s magnatron (in particular its vacuum cavity) inevitably leaks and gets less efficient over the years, and 20 years is getting towards double the expected lifespan. The noise is probably due to the leakage of air into the vacuum. Be happy with what you’ve got out of it and go buy a newer more efficient one.

Yes, it could be the bearings on the turntable below. That would be the grinding noise. The buzzing could indicate a problem developing in the secondary electronic circuit. That would be the transformer, magnetron and condenser. Microwaves are well protected for safety concerns, but it’s always better to be proactive. You have certainly gotten the best out of this appliance. I suggest you treat yourself to a new one. They are all lighter, smaller, and more efficient for the same sized cavity oven. And the price should be much cheaper than 20 years ago. The new one may not last 20 years though.