Read Sharp R-4G75M (serv.man3) Service Manual online
14
R-4G75(W)M
R-4G75(B)M
R-4G75(B)M
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT TEST
2-1 In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
b) When touching the pads, no pads produce a signal.
2-2 In connection with indicators
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.
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.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
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.
2-3 Other possible problems 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 obtainned.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtainned.
O
RELAY TEST
1. CARRY OUT 3D CHECKS
2. Disconnect the leads from the primary of the power transformer. Make sure that the leads remain
2. Disconnect the leads from the primary of the power transformer. Make sure that the leads remain
isolated from other oven components and chassis. (Use insulation tape if necessary.)
3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on the control unit with an A.C.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 3 and 5 of the 3 pin connector (A) on the control unit with an A.C.
voltmeter. The meter should indicat 240 volts, if not check oven circuit.
6. RY1, RY2 AND RY3 TEST
These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the
These 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,
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. 25.0V.D.C.
Oven lamp / Turntable motor / Cooling fan motor
RY2
Approx. 25.0V.D.C.
Power transformer
RY3
Approx. 25.0V.D.C.
Grill heater
CARRY OUT 4R CHECKS
N
KEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon is making
good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are
closed 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 connecter). Use
the Key unit matrix indicated on 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
good contact, verify that the door sensing switch (stop switch) operates properly; that is the contacts are
closed 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 connecter). Use
the Key unit matrix indicated on 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, itis a faulty and
must be replaced. If a spe-
cific pad does not re-
spond, the above method
may be used (after clear-
ing the control unit) to
determine if the control
unit or key pad is at fault.
must be replaced. If a spe-
cific pad does not re-
spond, the above method
may be used (after clear-
ing the control unit) to
determine if the control
unit or key pad is at fault.
KEY UNIT
G-8
G-7
G-6
G-5
G-4
G-3
G-2
G-1
G-9
G-10
G-11
G-12
10
SEC.
1
MIN.
10
MIN.
STOP
CLEAR
DUAL
COOK
GRILL
AUTO
MINUTE
START
AUTO
DEFROST
AUTO
COOK
MORE
LESS
g • oz
Kg • Lb
AUTO
START
Kg / Lb
POWER
LEVEL
TIMER
/HOLD
/HOLD
INSTANT
COOK
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