LG MH-658PMS Service Manual ▷ View online
5-15
(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 operation but little heat is produced in oven load.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1.Setting time does
not count down
when touching
START pad.
when touching
START pad.
2. Fan motor or
oven lamp
do not turn
on.
do not turn
on.
No continuity.
continuity.
No continuity.
Continuity.
Check the con-
nection between
connector and
P.C.B assembly.
nection between
connector and
P.C.B assembly.
Defective
secondary switch.
secondary switch.
Replace
secondary switch.
secondary switch.
Defective P.C.B
assembly.
assembly.
Replace P.C.B
assembly.
assembly.
Check continuity
of secondary
switch (with
door closed).
of secondary
switch (with
door closed).
Check fan motor.
Check oven lamp.
Abnormal.
Abnormal.
Normal.
Defective fan
motor.
motor.
Defective fan
motor.
motor.
Replace fan
motor.
motor.
Replace fan
motor.
motor.
Loose connection.
Connection then
tightly.
tightly.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Output is low.
Lower than 90% of
rating voltage.
rating voltage.
Normal.
Abnormal.
Abnormal.
Measure the
output power.
output power.
Disconnect the
wire leads from
relay 2 and check
on and off time
with multitester.
wire leads from
relay 2 and check
on and off time
with multitester.
Defective P.C.B
assembly.
assembly.
Replace P.C.B
assembly.
assembly.
Decrease in power
source voltage
with load.
source voltage
with load.
Suggest customer
contact local
electric power
utility co. or
qualified
electrician.
contact local
electric power
utility co. or
qualified
electrician.
Check the
power source
voltage.
power source
voltage.
Defective
magnetron.
magnetron.
Replace
magnetron.
magnetron.
NOTE: Simple test of power output-conducted by heating one liter water for one min. if available.
5-16
CONDITION
CHECK
RESULT
CAUSE
REMEDY
No microwave
oscillation.
oscillation.
No continuity.
Continuity.
Defective P.C.B
assembly
assembly
Replace P.C.B
assembly
assembly
Disconnect the
wire leads from
relay 2 and
check continuity
of relay2.
(Operate the
unit)
wire leads from
relay 2 and
check continuity
of relay2.
(Operate the
unit)
Abnormal
normal
Defective high
voltage
transformer.
voltage
transformer.
Replace high
voltage
transformer .
voltage
transformer .
Check H.V.
transformer.
transformer.
normal
normal
Abnormal
Defective high
voltage Diode.
voltage Diode.
Replace high
voltage Diode.
voltage Diode.
Check H.V.
diode.
diode.
Abnormal
Defective high
voltage capacitor.
voltage capacitor.
Replace high
voltage capacitor.
voltage capacitor.
Check H.V.
capacitor.
capacitor.
Abnormal
Defective
magnetron.
magnetron.
Replace
magnetron .
magnetron .
Check
Magnetron.
Magnetron.
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run
(Display operates properly)
5-17
(TROUBLE 7) Grill
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. Heater is not
operating.
Abnormal.
Normal.
Normal.
Heater.
Thermostat and
relay3.(Grill)
relay3.(Grill)
Abnormal.
Malfunction the
thermostat.
thermostat.
Malfunction the
heater.
heater.
Replace.
Wire connection.
No continuity.
Open or loosen.
Replace or
connect tightly.
connect tightly.
Replace.
1. Lower tempera-
ture the oven.
Abnormal.
Normal.
Heater.
Thermostat and
relay3.(Grill)
relay3.(Grill)
Abnormal.
Malfunction the
thermostat.
thermostat.
Malfunction the
heater.
heater.
Replace.
Replace.
(TROUBLE 6) Oven does not cook properly when programmed for the set power level
(Operates properly on HIGH)
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Output is full when
you set lower
power level.
power level.
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)
Defective P.C.B.
assembly.
assembly.
Replace P.C.B.
assembly.
assembly.
NOTE: * Make sure the wore leads correct position.
* When removing the wire leads from parts be sure to grasp the connector not the wires.
* When removing the magnetron, be sure to install the magnetron gasket in the correct position and in
* When removing the magnetron, be sure to install the magnetron gasket in the correct position and in
good condition.
MEASUREMENT WITH OUTER CASE
REMOVED
REMOVED
• When you replace the magnetron, measure for
microwave energy leakage before the outer case is
installed and after all necessary components are
replaced or adjusted.
installed and after all necessary components are
replaced or adjusted.
Special care should be taken in measuring the
following parts. (Circled area of below Fig.)
- Around the magnetron
- The waveguide
- The waveguide
MEASUREMENT WITH A FULLY
ASSEMBLED OVEN
ASSEMBLED OVEN
• After all components, including the outer case, are fully
assembled, measure for microwave energy leakage
around the door viewing window, the exhaust opening,
and air inlet openings.
around the door viewing window, the exhaust opening,
and air inlet openings.
• Microwave energy leakage must not exceed the values
prescribed below.
NOTE: Leakage with the outer case removedless than
5 mW/cm.sq. Leakage for a fully assembled
oven (Before the latch switch (primary) is
interrupted) with the door in a slightly opened
position-less than 2 mW/cm.sq.
oven (Before the latch switch (primary) is
interrupted) with the door in a slightly opened
position-less than 2 mW/cm.sq.
NOTES WHEN MEASURING
• Do not exceed meter full scale deflection.
• The test probe must be removed no faster than
• The test probe must be removed no faster than
1 inch/sec (2.5 cm/sec) along the shaded area,
otherwise a false reading may result.
otherwise a false reading may result.
• The test probe must be held with the grip portion of the
handle.
A false reading may result if the operator's hand is
between the handle and the probe.
• When testing near a corner of the door, keep the probe
perpendicular to the surface making sure the probe
horizontally along the oven surface, this may possibly
cause probe damage.
horizontally along the oven surface, this may possibly
cause probe damage.
RECORD KEEPING AND NOTIFICATION
AFTER MEASUREMENT
AFTER MEASUREMENT
• After adjustment and repair of any microwave energy
interruption or microwave energy blocking device,
record the measured values for future reference. Also
enter the information on the service invoice.
record the measured values for future reference. Also
enter the information on the service invoice.
• The microwave energy leakage should not be more
than 4 mW/cm.sq. after determining that all parts are in
good condition, functioning properly and genuine
replacement parts which are listed in this manual have
been used.
good condition, functioning properly and genuine
replacement parts which are listed in this manual have
been used.
• At least once a year, have the electromagnetic energy
leakage monitor checked for calibration by its
manufacturer.
manufacturer.
WARNING : AVOID CONTACTING ANY
HIGH VOLTAGE PARTS
5-2
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