R-21FBSTM - Sharp Home Appliance Service Manual (repair manual). Page 14

R-21FBSTM/R-22FBSTM - 14

Remove the outer case and check voltage between Pin No 1and Pin No 3 of the 3 pin connector (A) on
the control unit with an A.C. voltmeter.
The meter should indicate rated voltage, if not check oven circuit.

RY1,RY3 and RY4 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

CONNECTED COMPONENTS

RY1

Approx.   12.0V D.C.

Oven lamp / Turntable motor

RY3

Approx.   12.0V D.C.

High voltage transformer

RY4

Approx.   12.0V D.C.

Fan motor

If the display fails to clear when the STOP key is depressed, first verify the lead wire harness is
marking good contact, verify that the stop switch operates properly; that is the contacts are
closed when the door is closed and open when the door is open. If the stop switch is good,
disconnect the lead wire harness that connects the switch unit to the control unit and make sure
the stop switch is closed (either close the door or short the stop switch connecter). Use the
switch unit matrix indicated on the switch unit circuit and place a jumper wire between the pins
that correspond to the STOP key making momentary contact. If the control unit responds by
clearing with a beep the switch unit is faulty and must be replaced. If the control unit does not
respond, it is a faulty and must be replaced. If a specific key does not respond, the above
method may be used (after clearing the control unit) to determine if the control unit or switch
unit is at fault.

(J1

1

)

(J10)

13

12

10

11

ENCODER

A

B

C

RSW1

6

7

8

+1MIN

SW4

(J13)

(J12)

(J15)

(J14)

(J17)

(J16)

STOP

SW3

9

2

5

4

3

1

Switch unit

14

AUTOMATIC

SW1

SW2

4.7KF

12KF