Sharp R-939(BK), Service Manual

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R939(W)
8 – 3
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS.
[5] Procedure E: SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the following table.
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
[6] Procedure F: THERMISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect the connector B from CPU unit. Measure the resistance of the thermistor with an ohmmeter. Connect the ohmmeter leads to Pin No's C1
and C3 of the thermistor harness.
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
[7] Procedure G: THERMAL CUT-OUT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a continuity test across the two terminals as described
in the below.
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG) TC1 indicates that the magnetron has overheated, this may be due to resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (GRILL) TC2 indicates that the oven cavity has overheated, this may be due to no load operation.
An open circuit thermal cut-out (CONV.) TC3 indicates that the convection fan winding has overheated, this may be due to resistricted ventilation or
locked cooling fan or locked convection fan motor.
CARRY OUT 4R CHECKS.
[8] Procedure H: MOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two terminals as described in the table below.
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
Table: Terminal Connection of Switch
Plunger Operation Common terminal to Normally open terminal Common terminal to Normally close terminal
Released Open circuit Short circuit
Depressed Short circuit Open circuit.
Room Temperature Resistance
20
°
C - 30
°
C Approximately 359.9 k
Ω
- 152 k
Ω
Table: Thermal Cut-out Test
Parts Name
Temperature of “ON” condition
(closed circuit).
Temperature of “OFF” condition
(open circuit).
Indication of ohmmeter (When room
temperature is approx. 20
°
C.)
Thermal cut-out TC1 125
°
C This is not resetable type. Above 125
°
C Closed circuit
Thermal cut-out TC2 170
°
C Cuts back in at 155
°
C. Above 170
°
C Closed circuit
Thermal cut-out TC3 170
°
C Cuts back in at 155
°
C. Above 170
°
C Closed circuit
Table: Resistance of Motor
Motors Resistance
Fan motor Approximately 398.9
Ω
Turntable motor Approximately 14.7 k
Ω
Convection fan motor Approximately 183.7 k
Ω
Dumper motor Approximately 14.7 k
Ω