Test Procedures - Sharp R-530BK Service Manual

TEST PROCEDURES
Procedure Letter Component Test
A
.
Magnetron Assembly Test
1. Disconnect the power supply cord, and then remove outercase cabinet.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
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 IQ.
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 (shorted) and must be replaced.
6. Reconnect all leads removed from components during testing.
7. Re-install the outercase cabinet.
8. Reconnect the power supply cord after installing the outer case cabinet.
9. Run the oven and check all functions.
MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembeled
condition (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: high voltage rectifier, high voltage capacitor and power trans-
former. This test will require a 16 oz. (453~~) measuring cup and an accurate mercury thermometer
or thermocouple type temperature tester. For accurate results, the following procedure must be fol-
lowed:
Fill the measuring cup with 16 oz. (453~~) 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 on HIGH selecting 62 seconds cook time. Allow
the water to heat.
Remove the cup from the oven and again measure the temperature, making sure to stir the ther-
mometer or thermocouple through the water until the maximum temperature is recorded.
Subtract the cold water temperature from the hot water temperature. The normal result should
be 38" to 78°F (21 O to 42.6OC) rise in temperature. If the water temperatures are accurately mea-
sured and are 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 cook 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 120 volts and the oven cavity
is clean.
B
.
Power Transformer
1. Disconnect the power supply cord, and then remove outer case cabinet.
2. Open the door and block it open.
3. Discharge the high voltage capacitor.
4. Disconnect the primary input terminals and measure the resistance of the transformer with an ohm-
meter. 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 IR and the resistance of the high voltage coil should be approx-
imately IOOQ; the resistance of the filament coil should be less than 1 Q.
5. Reconnect all leads removed from components during testing.
6. Re-install the outercase cabinet.
7. Reconnect the power supply cord after installing the outer case cabinet.
8. Run the oven and check all functions.
Note: High voltages are present at the high voltage terminal, so do not attempt to measure the fila-
ment and high voltage.
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