Sharp R-22AM Service Manual page 17

PROCEDURE
LETTER
I TEMPERATURE FUSE TEST
1. CARRY OUT 3D CHECKS.
2. A continuity check across the temperature fuse terminals should indicate a closed circuit unless the
temperature of the temperature fuse reaches specfied temperature as shown below.
Magnetron tem-
perature fuse TF1
Magnetron tem-
perature fuse TF2
Blower motor tem-
perature fuse TF3
Oven temperature
fuse TF4
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE temperature fuse INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE,
J MONITOR RESISTOR R1 TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the monitor resistor R1. Using an ohmmeter and set on a low range. Check
between the terminals of the monitor resistor R1.
If incorrect readings are obtained, replace the monitor resistor R1.
CARRY OUT 4R CHECKS.
K THERMISTOR TEST
1. CARRY OUT 3D CHECKS.
2. Follow the procedures below for each thermistor.
2-1. MAGNETRON THERMISTOR TEST
Disconnect the connector of the magnetron thermistor from the switch harness. Measure the
resistance of the magnetron thermistor with an ohmmeter. Connect the ohmmeter leads to the leads
of the thermistor.
Room Temp.
Resistance
If the meter does not indicate above resistance, replace the thermistor.
2-2. OVEN THERMISTOR (1) TEST
Disconnect the connector of the oven thermistor (1) from the switch harness. Measure the resistance
of the oven thermistor (1) with an ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.
Room Temp.
Resistance
If the meter does not indicate above resistance, replace the thermistor.
2-3. OVEN THERMISTOR (2) TEST
Disconnect the two connectors of the magnetron thermistor and oven thermistor (2) from the switch
harness. Measure the resistance of the oven thermistor (2) with an ohmmeter. Connect the ohmmeter
leads to the leads of the thermistor.
TEST PROCEDURES
Open Close
temperature temperature
Non resetable
150˚C
type
Non resetable
120˚C
type
Non resetable
120˚C
type
REPLACE temperature fuse.
The resistance of monitor resistor R1 should be read approx. 4.3Ω.
59˚F (15˚C)
Approx. 373 kΩ
59˚F (15˚C)
Approx. 373 kΩ
COMPONENT TEST
Display or
Condition Check point
Magnetron MG1 Failure:
EE1
Test magnetron MG1 and Blower fan motor.
Magnetron MG1, MG2 Failure: Test magnetron MG1,
EE3
MG2. Check blower fan motor and ventilation opening.
Magnetron MG2 Failure:
EE2
Test magnetron MG2 and Blower fan motor.
Oven shut Check blower fan motor and ventilation opening or
rocked rotating of blower fan motor.
off
Food has been burned in oven.
Oven shut
off Temperature of oven inside is very high.
68˚F (20˚C)
Approx. 292 kΩ
68˚F (20˚C)
Approx. 292 kΩ
15
R-22AM
R-23AM
R - 2 3 A T
77˚F (25˚C)
Approx. 231 kΩ
77˚F (25˚C)
Approx. 231 kΩ