Sharp R-933 Service Manual page 21

Microwave oven with grill and convection
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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
JOG AND SWITCH UNIT TEST
If the display fails to clear when the STOP button
(tact switch SW13) is depressed, first verify the wire
harness is marking 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 wire
harness that connects the Jog and Switch unit to the
control unit and make sure the door sensing switch
is closed (either close the door or short the door
sensing switch connecter). Use the Jog and Switch
unit matrix indicated on the control panel schematic
and place a jumper wire between the pins that
correspond to the STOP button (tact switch SW13)
marking momentary contact. If the control unit re-
sponds by clearing with a beep the Jog and 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 button does not respond, the above
method may be used (after clearing the control unit)
to determine if the control unit or Jog and Switch unit
is at fault.
CARRY OUT 4R CHECKS.
O
RELAY TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between Pin Nos. 1 and 3 of the 4 pin connector (E) on the
control unit with an A.C. voltmeter.
The meter should indicate 230 volts, if not check oven circuit.
Relay Test
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation, grill
operation, convection operation or dual 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
RY3
RY4
RY5
RY6
RY7
RY8
CARRY OUT 4R CHECKS.
TEST PROCEDURES
COMPONENT TEST
control unit is defective.
OPERATIONAL VOLTAGE
Approx. 18.0V D.C.
Approx. 18.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
Approx. 24.0V D.C.
19
J-13
J-12
J-11
J-10
J - 9
J - 8
J - 7
J - 4
J - 3
SW1
SW2
AUTO
COOK
J - 6
SW5
SW6
EXPRESS
COOK
J - 5
SW9
SW10
WATT
J - 2
SW11
SW12
J - 1
CN - J
CONNECTED COMPONENTS
Oven lamp / Turntable motor
High voltage transformer
Grill (Top) heating element
Convection heating element
Touch control transformer
Fan motor
Convection motor
Damper motor
A
B
RSW1 ROTARY ENCODER
C
1
VR1 POTENTIOMETERS
2
3
SW3
SW4
SW7
SW8
AUTO
EXPRESS
REHEAT
DEFROST
SW13
STOP

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