Sharp R-21JCA-F service manual High Voltage Capacitor Test, Thermal CUT-OUT Test 125˚C Oven

R-21JCA-F

TEST PROCEDURES

PROCEDURE

LETTER

COMPONENT TEST

CHIGH VOLTAGE RECTIFIER TEST

1.Disconnect the power supply cord, and then remove outer case.

2.Open the door and block it open.

3.Discharge high voltage capacitor.

4.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.

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.

NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.

DHIGH VOLTAGE CAPACITOR TEST

1.Disconnect the power supply cord, and then remove outer case.

2.Open the door and block it open.

3.Discharge high voltage capacitor.

4.If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads and check for a short or open between the terminals using an ohmmeter.

Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate continuity for a short time and should indicate an open circuit once the capacitor is charged. If the above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either of the terminals and case. If it is shorted, replace the capacitor.

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.

ETHERMAL CUT-OUT TEST 125˚C (OVEN)

1.Disconnect the power supply cord, and then remove outer case.

2.Open the door and block it open.

3.Discharge high voltage capacitor.

4.A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the temperature of the thermal cut-out reaches approximately 257˚F(125˚C).

An open thermal cut-out indicates overheating of the oven, exchange the thermal cut-out and check inside of oven cavity and for improper setting of cooking time or operation of control unit. Check for restricted air flow through the vent holes of the oven cavity, especially the cooling fan and air guide.

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.

THERMAL CUT-OUT TEST 145˚C (MAGNETRON)

1.Disconnect the power supply cord, and then remove outer case.

2.Open the door and block it open.

3.Discharge high voltage capacitor.

4.A continuity check across the thermal cut-out terminals should indicate a closed circuit. If the temperature of the magnetron reaches approximately 293˚F(145˚C), the thermal cut-out opens. An open thermal cut- out indicates overheating of the magnetron. Check for restricted air flow to the magnetron, especially the cooling fan air guide.

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.

CAUTION: IF THE THERMAL CUT-OUT INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE, REPLACE THERMAL CUT-OUT.

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