Procedure L: Relay Test; Procedure M: Defrost Test; Procedure N: Foil Pattern On The Printed Wiring Board Test - Sharp R-426LS Service Manual

[13] Procedure L: 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 the cabinet side terminal of the relay RY1 and the lower side terminal of the relay RY2 on the
control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY1 and RY2 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.
DC. voltage indicated ................. Defective relay.
DC. voltage not indicated ........... Check diode which is connected to the relay coil. If diode is good, control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE
RY1
RY2
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.

[14] Procedure M: DEFROST TEST

WARNING: The oven should be fully assembled before following procedure.
1. Open the door.
2. Place one cup of water in the center of the turntable tray in the oven cavity.
3. Close the door, touch the "DEFROST" pad once.
4. Press "2", then press "5".
5. Touch the "START " pad.
6. The oven is in Defrost cooking condition.
7. The oven will operate as follows.
MENU 1ST STAGE
Steaks/Chops LEVEL
0.5lb 60%
8. If improper operation is indicated, the control unit is probably defective and should be checked.

[15] Procedure N: 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.
4) Follow the troubleshooting guide given below for repair.
STEPS OCCURRENCE
1 Only pattern at "a" is broken.
2 Pattern at "a" and "b" are broken. *Insert the coil RCILF2003YAZZ between "c" and "d".
5) Make a visual inspection of the varistor. Check for burned damage and examine the transformer with a tester for the presence of layer short-circuit
(check the primary coil resistance which is approximately 563Ω±10%). If any abnormal condition is detected, replace the control unit.
Approx. 12.0V D.C. Oven lamp / Turntable motor / Cooling fan motor
Approx. 12.0V D.C. Power transformer
2ND STAGE
TIME LEVEL TIME
20sec. 40% 20sec.
CAUSE OR CORRECTION
*Insert jumper wire J1 and solder.
CONNECTED COMPONENTS
3RD STAGE
LEVEL TIME
30% 45sec.
8 – 6
R426LS