R-269SLM (serv.man8). Test Procedures - Sharp Home Appliance Service Manual (repair manual). Page 4

R269WM

8 – 4

a) At a certain digit, all or some segments do not light up.

b) At a certain digit, brightness is low.

c) Only one indicator does not light up. 

d) The corresponding segments of all digits do not light up; or they continue to light up.

e) Wrong figure appears.

f) A certain group of indicators do not light up.

g) The figure of all digits flicker.

3) Other possible troubles caused by defective control unit.

a) Buzzer does not sound or continues to sound.

b) Clock does not operate properly.

c) Cooking is not possible.

1. CARRY OUT 3D CHECKS.

2. Isolate the key unit with the control panel frame to be tested.

3. Using an ohmmeter and referring to the key unit matrix indicated on the control unit circuit, check the circuit between the pins of the key unit that

correspond to the STOP/CLEAR key. When the pad is pressed, the ohmmeter should indicate short circuit. When the pad is released, the ohmme-
ter should indicate open circuit. If incorrect readings are obtained, the key unit is faulty and must be replaced. About the other pads, the above
method may be used.

4. CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between the normal open terminal of the relay RY1 and the normal open terminal of the relay RY2 on the
control unit with an A.C. voltmeter. The meter should indicate 230 - 240 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.

CARRY OUT 4R CHECKS.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

Approx. 12.9V D.C.

Oven lamp / Turntable motor / Cooling fan motor

RY2

Approx. 12.3V D.C.

High voltage transformer

Pin 10

Pin 1

G1

G2

G3

G4

G5

G6

G7

G8

G9

G10

10 sec.

1 min.

10 min

AUTO

COOK

MEAT

JOINT

ROAST BEEF

LAMB

ROAST

PORK

ROAST

POULTRY

TIME

WEIGHT

STOP

CLEAR

START

AUTO MINUTE

WEIGHT

POWER

LEVEL

TIME

KITCHEN TIMER

CLOCK SET

CHICKEN

QUATERS

WHOLE

POULTRY

Key unit (Membrane Switch) front view

Key unit ribbon cable