Over the years manufacturers have used several different methods to rate the output wattage of microwave ovens. First, there was the traditional method. Then, in 1989-90 came the JIS (Japanese Industrial Standard). Using the JIS method, ovens rated at 700 watts using the traditional method became 750-watt ovens. In 1990-91 the industry changed to the international IEC-705 standard. This pushed the wattage ratings even higher. For example, models rated at 700 traditional watts were instantly turned into 800-watt ovens using the IEC-705 formula.
The following test will provide a suitably accurate measurement of the output power of any microwave oven. Variations or errors in performing this test will produce uncertain results. If the line voltage (from the electrical outlet) is low, the magnetron output will be correspondingly low.
In order to evaluate the independent operation of each individual magnetron, the systems must first be isolated. This is accomplished by disabling one side, then performing an output power test on the functioning side. Either side may be disabled first.
Before touching components or wiring:Make sure the
oven is unplugged.
There is high voltage present, with high-current capabilities, in the circuits of the high voltage section. It is extremely dangerous to work on or near these circuits with the oven energized. DO NOT TOUCH components or wiring while the oven is operating. Use very great caution at all times.
The procedure is as follows. Observing the above safety precautions, first disable one side by carefully disconnecting one or both of the leads from the primary side of the high voltage transformer. (See the illustration to the right). Set the oven to cook at full power and do an output wattage check as outlined above. Having established the functional status of the one side, unplug the oven, discharge the high-voltage capacitors, re-connect the transformer primary wires, and repeat the procedure for the other side.