Sharp R-520LK ユーザーズマニュアル

14

1.  Disconnect the power supply cord, and then remove outer case.
.  Open the door and block it open.
3.  Discharge high voltage capacitor.
4.  Disconnect  the  primary  input  terminals  and  measure  the  resistance  of  the  transformer  with  an

ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance
of the primary coil should be less than 1 ohm and the resistance of the high voltage coil should be
approximately 90 ohms; the resistance of the filament coil should be less than 1 ohm.

5.  Reconnect all leads removed from components during testing.
6.  Reinstall the outer case (cabinet).
7.  Reconnect the power supply cord after the outer case is installed.
8.  Run the oven and check all functions.

(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASURE THE FILAMENT AND HIGH VOLTAGE.)

4.  To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check

across the magnetron filament leads should indicate less than 1 ohm.

5.  To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads

and chassis ground. This test should indicate an infinite resistance. If there is little or no resistance
the magnetron is grounded and must be replaced.

6.  Reconnect all leads removed from components during testing.
7.  Reinstall the outer case (cabinet).
8.  Reconnect the power supply cord after the outer case is installed.
9.  Run the oven and check all functions.

The following test procedure should be carried out with the microwave oven in a fully assembled condi-
tion (outer case fitted).

HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD
BE OBSERVED.

Power output of the magnetron can be measured by performing a water temperature rise test. This
test should only be used if above tests do not indicate a faulty magnetron and there is no defect in the
following components or wiring: silicon rectifier, high voltage capacitor and power transformer. This test
will require a 16 ounce (453cc) measuring cup and an accurate mercury thermometer or thermocouple
type temperature tester. For accurate results, the following procedure must be followed carefully:

1.  Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature of the water

with  a  thermometer  or  thermocouple  temperature  tester.  Stir  the  thermometer  or  thermocouple
through the water until the temperature stabilizes. Record the temperature of the water.

.  Place the cup of water in the oven. Operate oven at POWER 10(HIGH) selecting more than 60

seconds cook time. Allow the water to heat for 60 seconds, measuring with a stop watch, second
hand of a watch or the digital read-out countdown.

3.  Remove  the  cup  from  the  oven  and  again  measure  the  temperature,  making  sure  to  stir  the

thermometer or thermocouple through the water until the maximum temperature is recorded.

4.  Subtract the cold water temperature from the hot water temperature. The normal result should be

33 to 6

O

F(18.6 to 34.5

O

C) rise in temperature. If the water temperatures are accurately measured

and tested for the required time period the test results will indicate if the magnetron tube has low
power output (low rise in water temperature) which would extend cooking time or high power output
(high rise in water temperature) which would reduce cooking time. Because cooking time can be
adjusted to compensate for power output, the magnetron tube assembly should be replaced only if
the water temperature rise test indicates a power output well beyond the normal limits. The test is
only accurate if the power supply line voltage is 10 volts and the oven cavity is clean.