Testing a home microwave Magnetron.

I've made the two common tests on a home microwave magnetron. The second test is o.k. (on maximum Ω scale both terminals show no resistance at all when measured between the ground). The first test (measuring both terminals among them at minimum Ω scale) shows a result of 3.6Ω instead of the "less-than 1Ω" that you indicated in a past thread to someone else. Does that mean that there is something wrong with the magnetron?

Unlikely.

By "no resistance" I assume you mean no reading rather than zero (short circuit). There should be no conduction at all between the anode and filament (cathode) but there should be a low resistance from one filament connection to the other. 3.6 Ohms isn't unreasonable if you are measuring it out of circuit. When installed, it will have a few turns of copper wire in the transformer connected across the filament so it will measure < 1 Ohm.

Brian.

By "no resistance" I meant that the reading in the digital multimeter was "1" (open). My real concern is that originally the measurement for the first test was 0.76 Ohms but there was an accident and the magnetron received a bump, after that it measures 3.6 Ohms, perhaps the filament was damaged by the bump. I'm afraid if I connect it to work it is going to make some sort of short circuit or explosion that might damage the HV transformer.

They are very robust, a knock wouldn't change the filament resistance. More likely, because the resistance is very low anyway, the probe contact or even the meter cable resistance was also playing a part in the measurement.

There is actually very little inside a Magnetron, a shaped cavity, a heating filament and a strong magnet so the chances of something breaking are slim. They are simple devices, the heater is also the negative electrode and it emits electrons. The cavity is the positive electrode that attracts the electrons toward it. The magnet skews the electron flow so it passes over the entrance to the cavity and sets up an oscillation. It's the same principle as blowing over the neck of a bottle making a tone except with electrons instead of wind. The size of the cavity decides the frequency just like the size of the bottle would.

You should be able to measure resistance across the heating filament, it is only a wire, much like the filament in an incandescent light bulb. You should not be able to measure resistance to the cavity (anode) becuase there is a vacuum gap between it and the filament.

Brian.

I will assemble the oven and connect it to see what happens. I'll let you know! Thks.

A microwave we had stopped working, on investigating it was that one of the Faston filament connectors was burnt up, replaced it and it went on for another 10 years.
Frank