H4-72-02-03
10
For internal use only
5.2
Checking the diode
1. Disconnect the high-voltage conducting wires from the magnetron.
2. Measure the resistance at the supply points. A good magnetron will have a heating filament resist-
ance of less than 1
Ω
.
3. Measure the resistance between each terminal and the magnetron shell. The resistance between
each terminal and the shell of a good magnetron will be infinite.
Note!
• It is not possible to recognise all of the magnetron faults on the basis of resistance readings.
• It is difficult to determine an internal jump (short circuit) between anode and cathode.
• When examining the magnetron look out for burns around the antenna and for flawed magnets and
also check the terminals.
• It may also be possible to determine some magnetron faults by means of an audio test (buzzing and
rattling when the microwave oven is in operation).
5.3
Checking the converter switch
5.3.1
Checking the converter for a short circuit
The converter switch will probably have short-circuited if the 8A safety fuse of the microwave oven
triggers.
1. Disconnect all the conducting wires from the converter.
2. Remove the converter.
3. Check the three components indicated on the drawing by
measuring the switch resistance. Defect components will
generally have a very low resistance (almost 0
Ω
).
Measuring point
Normal
Fault
Between the terminals
< 1
Ω
∞
Between terminal and shell
∞
Fewer watts
