Sharp Carousel R-990K, Service Manual

R990K(W)

8 – 5

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.

[14] Procedure N: KEY UNIT (MEMBRANE SWITCH) TEST

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

[15] Procedure O: RELAY TEST

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between Pin No 9 of the 5-pin connector (A) and the common terminal of the relay RY1 on the control unit
with an A.C. voltmeter. The meter should indicate230 - 240 volts, if not check oven circuit.

Shut-off, Cook and Heater 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 convection 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.

[16] Procedure P: PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE
PRINTED WIRING BOARD (PWB) IS OPEN

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.

RELAY SYMBOL

OPERATIONAL VOLTAGE

CONNECTED COMPONENTS

RY1

APPROX. 21.0V D.C.

Oven lamp / Turntable motor

RY2(COOK)

APPROX. 21.0V D.C.

Power transformer

RY3(HEATER)

APPROX. 20.0V D.C.

Heating element

RY4

APPROX. 21.0V D.C.

Damper motor

RY5

APPROX. 21.0V D.C.

Convection motor

RY6

APPROX. 21.0V D.C.

Cooling fan motor

STEPS

OCCURRENCE

CAUSE OR CORRECTION

1

The rated voltage is not applied between Pin No. 9 of the 5-pin connector (A) 
and the common terminal of the relay RY1.

Check supply voltage and oven power cord.

1

2

3

4

5

6

7

8

9

0

STOP

CLEAR

REHEAT

PIE

EASY

DEFROST

LESS

POWER

LEVEL

40°C

70°C

130°C

150°C

160°C

180°C

200°C

220°C

230°C

250°C

HIGH MIX

LOW MIX

CONVEC

GRILL

MEMORY

PREHEAT

CLOCK

HELP

REHEAT

SENSOR

MULTI
COOK

FROZEN

VEGETABLES

FRESH

VEGETABLES

DESSERTS

JACKET

POTATO

INSTANT COOK

START

MORE

CASSEROLES

G 1

G 2

G 3

G 4

G 5

G 6

G 7

G 8

G 9

G10

G11

G12