Procedure L: Relay Test; Procedure M: Foil Pattern On The Printed Wiring Board Test - Sharp R-21LTF Service Manual

R21LTF
G 1 G 2
G 9
G10
G11
G12

[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 Pin Numbers. 3 and 7 of the connector (A) on the control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY2 and RY3 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
RY2
RY3
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: 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
G 3 G 4 G 5
17
SELECTA DOUBLE
7
POWER QUANTITY
18
SELECTA EXPRESS
8
TIME DEFROST
19 15 13
9 5
20 16 14
0 6
R-21LTF
G 9
G10
G11
G12
Approx. 12.0V D.C. Power transformer
Approx. 12.0V D.C. Oven lamp / Antenna motor / Cooling fan motor
CAUSE OR CORRECTION
G 6 G 7 G 8
START SET
STOP/
CHECK
CLEAR
11
3 1
SIGNAL
12
4 2
G 1 G 2 G 3
CONNECTED COMPONENTS
8 – 6
G 4 G 5 G 6 G 7
DOUBLE
7
START
QUANTITY
SELECTA EXPRESS STOP/
8
TIME CLEAR
DEFROST
9 5 3 1
0 6 4 2
R-21LVF
G 8
SET
CHECK
SIGNAL