Sharp R-980J Service Manual page 19

PROCEDURE
LETTER
2-3 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.
d) Proper temperature measurement is not obtained.
N KEY UNIT 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 sensing 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 key pad is at fault.
G 4
G 3
G 2
G 1
O RELAY TEST
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 indicate
230 - 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,
RELAY SYMBOL
RY1
RY2(COOK)
RY3(HEATER)
RY4
RY5
RY6
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.
TEST PROCEDURES
COMPONENT TEST
G 5 G 6 G 7
control unit is defective.
OPERATIONAL VOLTAGE
APPROX. 21.0V D.C.
APPROX. 21.0V D.C.
APPROX. 20.0V D.C.
APPROX. 21.0V D.C.
APPROX. 21.0V D.C.
APPROX. 21.0V D.C.
17
G 8 G 9 G10
CONNECTED COMPONENTS
Oven lamp / Turntable motor
Power transformer
Heating element
Damper motor
Convection motor
Cooling fan motor
R-980J
G11 G12