R-734 (serv.man4). Complete - Sharp Home Appliance Service Manual (repair manual). Page 18

R-734 - 18

Remove the outer case and check voltage between Pin No. 1 and 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, 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 or grill
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. 24.0V D.C.

Oven lamp / Turntable motor / Cooling fan motor

RY2

Approx. 18.0V D.C.

Heating element

RY3

Approx. 18.0V D.C.

High voltage transformer

If the display fails to clear when the STOP key is
depressed, first verify the lead wire harness is mak-
ing good contact, verify that the stop switch operates
properly; that  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 display unit and make
sure the stop switch is closed (either close the door
or short the stop switch connector). Use the Switch
unit matrix indicated on the switch unit circuit and
place a jumper wire between the pins that corre-
spond to the STOP key making momentary contact.
If the display unit responds by clearing with a beep
the switch unit is faulty and must be replaced. If the
display 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 dis-
play unit) to determine if the display unit or switch unit
is at fault.

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. If the foil pattern is open, follow the troubleshooting guide given
below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated AC voltage is not present at

Check supply voltage and oven power cord.

POWER terminal of CPU connector (CN-A).

2

The rated AC voltage is present at primary

Low voltage transformer or secondary circuit defective.

side of low voltage transformer.

Check and repair.

3

Only pattern at "a" is broken.

*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)

4

Pattern at "a" and "b" are broken.

*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)

1

2

3

4

SW2

5

6

SW3

SW4

SW5

SW6

SW7

SW1