Sharp R-90GCH Service Manual page 23

PROCEDURE
LETTER
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurment is not obtained.
When testing is completed, CARRY OUT 4R CHECKS.
W TACT SWITCH TEST
1. CARRY OUT 3D CHECKS.
2. By using an ohmmeter, check the tact switch operation.
3. When the tact switch is not depressed, an ohmmeter should indicate an open circuit. When the
tact switch is depressed, an ohmmeter should indicate a short circuit. If improper operation is
indicated, the tact switch is probably defective and should be checked.
X RELAY TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads to the primary of the high voltage transformer.
3. Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
4. After that procedure, re-connect the power supply cord.
5. Remove the outer case and check voltage between Pin Nos. 1 and 9 of the 5 pin connector (CN-
D) on the control unit with an A.C. voltmeter. The meter should indicate the rated voltage, if not
check oven circuit.
Shut-off, Cook and Heater Relays Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, grill,
dual1, dual2, preheating, or convection cooking condition.
DC. voltage indicated ............... Defective relay.
DC. voltage not indicated ......... Check diode which is connected to the relay coil. If diode is
RELAY SYMBOL
RY1
RY2 (COOK)
RY3
RY4
RY5
RY6
6. CARRY OUT 4R CHECKS.
Y SOLID-STATE RELAY TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads from the solid-state relay.
3. Measure the resistance between the terminals as described in the following table, with an
ohmmeter.
4. If the meter does not indicate above resistance, replace the solid-state relay.
5. CARRY OUT 4R CHECKS.
Z PROCEDURES TO BE TAKEN WHEN THE FUSE 1 ON THE PRINTED WIRING BOARD
(PWB) IS OPEN AND TOUCH CONTROL TRANSFORMER TEST.
To protect the electronic circuits, this model is provided with a fuse added to the primary on the PWB.
1. Fuse 1 check and repairs and touch control transformer test.
TEST PROCEDURES
COMPONENT TEST
good, control unit is defective.
OPERATIONAL VOLTAGE
Approx. 18V D.C.
Approx. 18V D.C.
Approx. 24V D.C.
Approx. 24V D.C.
Approx. 24V D.C.
Approx. 24V D.C.
Terminals
Between 1 and 2
Between 3 and 4
21
CONNECTED COMPONENTS
Oven lamp / Turntable motor
High voltage transformer
Convection motor
Damper motor
Fan motor
Convection motor
Resistance
Approx. 50MΩ
Approx. 1.3MΩ
R-90GCH
1 2
3 4
Solid-state relay