Specifications

Ver SG 9/200 25 Sharp Electronics Corporation
Another failure that can not be easily detected is the weak magnetron. After years of
operation the amount of electrons that the cathode can release is reduced. The charge that
is carried in the cloud of electrons is diminished and the amount of energy transferred to
the resonate cavities is also reduced. This failure can not be avoided and is in proportion
to the amount of time the oven is used. To detect a weak magnetron a running wattage
test must be taken.
During the 1990 product year the microwave industry standardized the rating
specifications for output power. The ovens prior to 1990 used the 2-liter water load
rating standard . Ovens during 1990 used both the 2-liter method and the new IEC-705
test procedure. When you troubleshoot an oven and suspect the magnetron has low
output make sure you check the method used to initially rate the oven. If you use the 2-
liter method on an oven which was initially rated by the IEC-705 method the output will
be drastically lower. This of course would cause you to replace the magnetron and
incorrectly diagnose the trouble.
Due to the complex formula and the precision required to successfully check the output,
we recommend you use the following guidelines for testing a suspected weak magnetron.
Power output of the magnetron can be determined by performing a water temperature rise
test. This test should only be used if the circuits check good in all the prior ohmmeter
tests. This test requires a 16-ounce cup and an accurate mercury thermometer. For
accurate results, the following procedure must be followed carefully:
1. Fill the measuring cup with 16 ounces of tap water and measure the temperature of
the water with the thermometer. Stir the thermometer through the water until the
temperature stabilizes. Record the temperature of the water.
2. Place the cup of water in the oven, selecting more than 60 seconds of cooking time.
Allow the water to heat for 60 seconds, measuring the time with a stopwatch, second
hand, or digital read out countdown.
3. Remove the cup from the oven and again measure the temperature, making sure to
stir the thermometer through the water until maximum temperature is reached.
4. Subtract the cold water temperature from the hot water temperature. The normal
result should be:
15-28 degrees Fahrenheit if testing a 600 watt oven
18-33 degrees Fahrenheit if testing a 700 watt oven
21-39 degrees Fahrenheit if testing a 850 watt oven
22-43 degrees Fahrenheit if testing a 900 watt oven
27.7-51.5 degrees Fahrenheit if testing a 950 watt oven
34.7-64.6 degrees Fahrenheit if testing a 1000 watt oven
32.6-64.6 degrees Fahrenheit if testing a 1100 watt oven