Sharp Carousel R-930AK Manuale di servizio - Pagina 16

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R-930AK

R-930AW

PROCEDURE

LETTER

MAGNETRON ASSEMBLY TEST

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

BE OBSERVED.

DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS

OR WIRING.

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.

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.

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.

2. Place the cup of water in the oven. Operate oven at POWER HI(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 22

to 43˚F(12.2 to 23.8˚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 120 volts and the oven cavity is clean.

POWER TRANSFORMER TEST

DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS

OR WIRING.

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 84.4 ohms;

the resistance of the filament coil should be less than 1 ohm.

(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO

MEASURE THE FILAMENT AND HIGH VOLTAGE.)

HIGH VOLTAGE RECTIFIER TEST

DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS

OR WIRING.

Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance across

the terminals and observe, reverse the leads to the rectifier terminals and observe meter reading. If a

short is indicated in both directions, or if an infinite resistance is read in both directions, the rectifier is

probably defective and should be replaced.

HIGH VOLTAGE CAPACITOR TEST

DISCHARGE THE HIGH VOLTAGE CAPACITOR BEFORE TOUCHING ANY OVEN COMPONENTS

OR WIRING.

TEST PROCEDURES

COMPONENT TEST