Peter Hucker wrote:
On Fri, 19 Jan 2007 20:26:35 -0000, Jon Elson wrote:



Peter Hucker wrote:


Is it really true that turning on a microwave with nothing in it will break it?

Even more worrying - will it catch fire or explode?

Don't they have a safety cutout? Can't it sense the Klystron overheating,


That would be a Magnetron tube, and yes, I thenk they all have a
thermostat on
the tube. This is also to prevent a fire if the cooling fan seizes up.
But, in the
case of no food to absorb the microwave energy, the reflected power can
build up
higher than normal voltages in the tube and cause permanent damage
before the
entire anode overheats.


So it'll just break? That's good to know. I don't want to lose a house or a parrot while out at work.

Well, if it has the safety thermostat on the anode, then it will
just shut down, probably forever. I have no idea whether the
safety thermostat is mandated by law or required by testing
agencies like UL, and whether the really cheap ones from China
have them. Without the safety stat, I don't know what would happen.


That's a point, it must happen a lot. If they caught fire or exploded, we'd see it on the news.

Well, I think there have been some fires from them, but probably
not a lot.


I once went for an interview at a company that makes magnetrons. As far as I know there is a thing that absorbs all returning microwaves. Wouldn't this just have a temperature sensor in it that would shut off the oven?
Not in an oven. Maybe in a radar transmitter, they have an
expensive part called a circulator that splits waves going in
different directions, and shunts returning waves to a terminating
resistor. Nothing like that in a microwave oven, believe me.

Jon