LG MG-5355D Service Manual ▷ View online
5-14
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. Fuse blows.
Continuity.
No continuity.
Continuity.
Shorted contact
the primary switch.
the primary switch.
Replace primary
and monitor
switch.
and monitor
switch.
No continuity.
Normal.
Defective high
voltage capacitor.
voltage capacitor.
Replace high volt-
age capacitor.
age capacitor.
Fuse blows again
Defective high vo-
ltage transformer.
ltage transformer.
Defective high vo-
ltage transformer.
ltage transformer.
Malfunciton of the
monitor switch.
monitor switch.
Replace primary,
and monitor
switch.
and monitor
switch.
Check continuity
of monitor
switch (with
door closed).
of monitor
switch (with
door closed).
Check continuity
of primary
switch (with
door opened).
of primary
switch (with
door opened).
Disconnect one side of the wire
lead connected from transformer
to the high voltage capacitor and
operate the unit.
lead connected from transformer
to the high voltage capacitor and
operate the unit.
Replace fuse
2. Fuse does not
blow.
No continuity.
Continuity.
No continuity.
Defective power
supply cord.
supply cord.
Replace power
supply cord.
supply cord.
Defective mag-
netron thermostat.
netron thermostat.
Replace magen-
tron thermostat.
tron thermostat.
Check continuity
of magnetron
thermostat.
of magnetron
thermostat.
Check continuity
of power supply
cord.
of power supply
cord.
(TROUBLE 2) Oven does not operate at all ; Display window does not display any figures
and no input is accepted.
NOTE :
•
All these switches must be replaced at the same time. Refer to page 5-6, 5-7.
5-15
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. Setting time
does not count-
down when
touching START
pad.
down when
touching START
pad.
2. Fan motor or
oven lamp do
not turn on.
not turn on.
No continuity.
Continuity.
Certainly
Defective PCB
assembly.
assembly.
Loose connection.
Replace PCB
assembly.
assembly.
Connect them
tightly.
tightly.
No certainly.
Abnormal
Check fan motor.
Defective fan motor.
Replace fan motor.
Abnormal
Check oven lamp.
Defective oven lamp.
Replace oven lamp.
Defective sec-
ondary switch.
ondary switch.
Replace sec-
ondary switch.
ondary switch.
Check continuity
of secondary
switch (with
door closed).
of secondary
switch (with
door closed).
Check the con-
nection between
3 pin connector
and PCB
assembly.
nection between
3 pin connector
and PCB
assembly.
Normal
Defective PCB
assembly.
assembly.
Replace PCB
assembly.
assembly.
(TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired
program times are set and START pad is touched.
(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.
NOTE : Simple test of power output-conducted by heating one liter water for one min. if available.
Minimum 8.5°C temperature rise is normal condition.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Output is low
Lower than 90% of
rating voltage.
rating voltage.
Normal
Abnormal
Defective PCB
assembly.
assembly.
Replace PCB
assembly.
assembly.
Normal
Abnormal
Measure the out-
put power.
put power.
Defective mag-
netron.
netron.
Replace mag-
netron.
netron.
Decrease in power
source voltage
with load.
source voltage
with load.
Suggest customer
contact local elec-
tric power utility
co. or qualified
electrician.
contact local elec-
tric power utility
co. or qualified
electrician.
Check the
power source
voltage.
power source
voltage.
Disconnect the
wire leads from
relay 2 and
check on and off
time with multi-
tester.
wire leads from
relay 2 and
check on and off
time with multi-
tester.
5-16
CONDITION
CHECK
RESULT
CAUSE
REMEDY
No continuity.
Check monitor
fuse
fuse
No microwave
oscilation.
oscilation.
Continuity.
Abnormal resis-
tance or burn-out.
tance or burn-out.
Defective A.C.
relay or defective
montitor resistor.
relay or defective
montitor resistor.
Replace faulty
component.
(AC relay and/or
monitor resistor)
component.
(AC relay and/or
monitor resistor)
Normal.
Defective primary
switch or defective
monitor fuse.
switch or defective
monitor fuse.
Replace primary
switch and
monitor fuse.
switch and
monitor fuse.
Check monitor
resistor.
resistor.
No continuity.
Defective PCB
assembly.
assembly.
Replace PCB
assimbly.
assimbly.
Continuity.
Disconnect the
wire leads from
relay 2 and check
continuity of relay
2. (Operate the
unit)
wire leads from
relay 2 and check
continuity of relay
2. (Operate the
unit)
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.
(Display operates properly)
Abnormal
Defective high
voltage fuse.
voltage fuse.
Replace high
voltage fuse.
voltage fuse.
Normal
Check high
voltage fuse.
voltage fuse.
Abnormal
Defective high
voltage trans-
former.
voltage trans-
former.
Replace high
voltage trans-
former.
voltage trans-
former.
Normal
Check high volt-
age transformer.
age transformer.
Abnormal
Defective high
voltage capacitor.
voltage capacitor.
Replace high
voltage capacitor.
voltage capacitor.
Normal
Check high volt-
age capacitor.
age capacitor.
Abnormal
Defective high
voltage diode.
voltage diode.
Replace high
voltage diode.
voltage diode.
Normal
Check high
voltage diode.
voltage diode.
Abnormal
Defective
magnetron.
magnetron.
Replace
magnetron.
magnetron.
Check
magnetron.
magnetron.
5-17
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Abnormal.
Disconnect the
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)
Output is full when
you set lower
power level.
you set lower
power level.
2. Lower tempera
ture in the oven.
1. Heater is not
operating.
Defective PCB
assembly
assembly
Replace PCB
assembly
assembly
(TROUBLE 6) Oven does not cook properly when programmed for the set power level
(Operates properly on HIGH)
CONDITION
CHECK
RESULT
CAUSE
REMEDY
(TROUBLE 7) Grill
Abnormal.
Malfunction the
heater.
heater.
Replace.
Normal.
Heater.
Abnormal.
Malfunction the
thermostat.
thermostat.
Replace.
Normal.
Thermostat
(Grill).
(Grill).
No continuity.
Open or loosen.
Replace or
Connct tightly.
Connct tightly.
Wire connec-
tion.
tion.
Abnormal.
Malfunction the
heater.
heater.
Replace.
Normal.
Heater.
Abnormal.
Malfunction the
thermostat.
thermostat.
Replace.
Thermostat
(Grill).
(Grill).
NOTE :
•
Make sure the wire leads correct position.
•
When removing the wire leads from the parts, be sure to grasp the connector
not the wires.
not the wires.
•
When removing the magnetron, be sure to install the magnetron gasket in the
correct position and in good condition.
correct position and in good condition.
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