Sharp R-55TS Service Manual page 21

PROCEDURE
LETTER
N RELAY 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. Disconnect the leads to the primary of the power transformer.
5. Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
6. After that procedure, re-connect the power supply cord.
7. Remove the outer case and check voltage between Pin Nos. 5 and 7 of the 7 pin connector (A) on
the control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
Shut off, Cook and Heater Relay 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
cooking operation, or bake cooking operation.
DC. voltage indicated ............. Defective relay.
DC. voltage not indicated ........ Check diode which is connected to the relay coil. If diode is good, control
RELAY SYMBOL
SELECT RELAY
8. Disconnect the power supply cord, and then remove outer case.
9. Open the door and block it open.
10.Discharge high voltage capacitor.
11.Reconnect all leads removed from components during testing.
12.Re-install the outer case (cabinet).
13.Reconnect the power supply cord after the outer case is installed.
14.Run the oven and check all functions.
O EXPRESS DEFROST TEST
WARNING : The oven should be fully assembled before following procedure.
(1) Place one cup of water in the center of the turntable tray in the oven cavity.
(2) Close the door, touch the " Express Defrost " pad once and touch the "START" pad.
(3) The oven is in Express Defrost cooking condition.
(4) The oven will operate as follows
WEIGHT
0.5lb
(5) If improper operation is indicated, the control unit is probably defective and should be checked.
P FOIL PATTERN ON THE PRINTED WIRING BOARD TEST
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
the PWB, this foil pattern acts as a fuse.
1. Foil pattern check and repairs.
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
TEST PROCEDURES
unit is defective.
OPERATIONAL VOLTAGE
RY1 Approx. 24.2V D.C.
RY2 Approx. 23.4V D.C.
RY3 Approx. 23.4V D.C.
RY4 Approx. 23.4V D.C.
RY5 Approx. 24.2V D.C.
Approx. 23.4V D.C.
1ST STAGE
LEVEL TIME
70% 1min. 2sec.
COMPONENT TEST
Oven lamp/ Turntable motor
Power transformer/ Upper heater/ Lower heater
Upper heater
Lower heater
Fan motor
Power transformer/ Upper heater/ Lower heater
2ND STAGE 3RD STAGE
LEVEL TIME LEVEL
0% 1min. 2sec. 50%
19
CONNECTED COMPONENTS
4TH STAGE
TIME LEVEL
32sec. 30%
R-55TS
TIME
50sec.