Sharp R-953(SL)M Service Manual page 16

TEST PROCEDURES
PROCEDURE
LETTER
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 indiicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
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.
Parts Name
Thermal cut-out 125˚C
Thermal cut-out 170˚C (GRILL)
Thermal cut-out 170˚C (CONV.)
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG) indicates that the magnetron has overheated, this may be due to
resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (GRILL) indicates that the oven cavity has overheated, this may be due
to no load operation.
An open circuit thermal cut-out (CONV.) indicates that the convection fan motor winding has over
heated, this may be due to resisted ventilation or locked cooling fan or locked convection fan motor.
CARRY OUT 4R CHECKS.
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.
I NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as described in the following table.
Room Temperature
20˚C - 30˚C
Temperature of
"ON" condition
(closed circuit).
This is not resetable
Below 155˚C.
Below 155˚C.
Table: Resistance of Motor
Motors
Fan motor
Turntable motor
Convection fan motor
Damper motor
R-953/963M - 14
COMPONENT TEST
Resistance
Approximately 359.9 kΩ - 152 kΩ
Table: Thermal Cut-out Test
Temperature of
"OFF"condition
(open circuit).
Above 125˚C
Above 170˚C
Above 170˚C
Resistance
Approximately
Approximately
Approximately
Approximately
Indication of ohmmeter
(When room temperature
is approx. 20˚C.)
Closed circuit
Closed circuit
Closed circuit
293 Ω
15 kΩ
288 Ω
11 kΩ