LG MS-190A Service Manual ▷ View online
5-14
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. Fuse blows.
Continuity.
No continuity.
Continuity.
Shorted contact at
the primary switch.
the primary switch.
Replace fuse,
primary, monitor
and secondary
switches.
primary, monitor
and secondary
switches.
No continuity.
Normal.
Defective high
voltage capacitor.
voltage capacitor.
Replace high
voltage capacitor.
voltage capacitor.
Fuse blows again
Defective high volt-
age transformer.
age transformer.
Replace high volt-
age transformer.
age transformer.
Malfunction of the
monitor switch.
monitor switch.
Replace fuse,
primary, monitor
and secondary
switches.
primary, monitor
and secondary
switches.
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.
side of the wire
lead connected
from transformer
to the high
voltage
capacitor and
operate the unit.
Replace fuse
1. Oven does not
operate.
No continuity.
No continuity.
Adjust or replace.
Malfunction of the
primary switch.
primary switch.
Malfunction of the
secondary switch.
secondary switch.
Adjust or replace.
Check the
continuity of the
primary switch
with door
closed.
continuity of the
primary switch
with door
closed.
Check the
continuity of the
secondary
switch with
secondary
switch pushed.
continuity of the
secondary
switch with
secondary
switch pushed.
(TROUBLE 1) Oven lamp does not turn on when the timer knob is pushed with door closed.
(TROUBLE 2) Oven does not start even though the timer is set.
NOTE : All these switches must be replaced at the same time.
This fuse is a special type of fuse which is kept as spare part by the importer.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
5-15
(TROUBLE 3) Output power is low.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Output is low
Lower than 207V.
Normal
Less than 8.5
°
C.
Measure the
magnetron and
H.V.T, H.V.C
output(See test
procedure).
magnetron and
H.V.T, H.V.C
output(See test
procedure).
Faulty H.V.T,
H.V.C magnetron.
H.V.C magnetron.
Replace.
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
oscillating.
power source
voltage
oscillating.
No continuity.
No continuity.
replace.
Malfunction of the
timer switch.
timer switch.
Faulty thermostat.
replace.
Check the
continuity of the
timer switch
contacts.
continuity of the
timer switch
contacts.
Check the
continuity of the
thermostat.
continuity of the
thermostat.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
5-16
CONDITION
CHECK
RESULT
CAUSE
REMEDY
No microwave
oscillation.
oscillation.
No continuity.
Continuity.
Malfunction of the
power control
switch.
power control
switch.
Replace the power
control switch.
control switch.
Check the
power control
switch(cooking
state).
power control
switch(cooking
state).
Abnormal
Open the
secondary winding
of the high voltage
transformer of
faulty insulation of
filament winding.
secondary winding
of the high voltage
transformer of
faulty insulation of
filament winding.
Replace .
Check H.V.
transformer.
transformer.
Abnormal
Shorted H.V. diode
Replace .
Check H.V.
diode.
diode.
Abnormal
Faulty capacitor.
Replace .
Check H.V.
capacitor.
capacitor.
Abnormal
Faulty magnetron.
Replace .
Magnetron
(TROUBLE 4) Oven does not cook at all even though turntable rotates.
NECESSARY TOOLS
Tools normally used for TV servicing are sufficient.
Standard tools are listed below.
Standard tools are listed below.
• Diagonal pliers
• Long nose pliers
• Phillips screwdriver
• Flat blade screwdriver
• Wrench (size 5mm)
• Nutdriver (size 5mm)
• Adjustable wrench
• Soldering iron
• Solder
• Vinyl insulation tape
• Polishing cloth
• Long nose pliers
• Phillips screwdriver
• Flat blade screwdriver
• Wrench (size 5mm)
• Nutdriver (size 5mm)
• Adjustable wrench
• Soldering iron
• Solder
• Vinyl insulation tape
• Polishing cloth
CAUTIONS
• Be sure to check microwave leakage prior to
servicing the oven if the oven is operative prior to
servicing.
servicing.
• The service personnel should inform the
manufacturer, importer, or assembler of any
certified oven unit found to have a microwave
emission level in excess of 5 mW/cm
certified oven unit found to have a microwave
emission level in excess of 5 mW/cm
2
and should
repair any unit found to have excessive emission levels
at no cost to the owner and should ascertain the cause
of the excessive leakage. The service personnel
should instruct the owner not to use the unit until the
oven has been brought into compliance.
at no cost to the owner and should ascertain the cause
of the excessive leakage. The service personnel
should instruct the owner not to use the unit until the
oven has been brought into compliance.
• If the oven operates with the door open, the service
personnel should:
- Tell the user not to operate the oven.
- Contact the manufacturer.
- Contact the manufacturer.
• The service personnel should check all surface and
vent openings for microwave leakage.
• Check for microwave leakage after every servicing. The
power density of the microwave radiation leakage
emitted by the microwave oven should not exceed
5 mW/cm
emitted by the microwave oven should not exceed
5 mW/cm
2
. Always start measuring of an unknown field
to assure safety for operating personnel from radiation
leakage.
leakage.
NECESSARY MEASURING INSTRUMENTS
• TESTER(VOLTS-DC, AC., Ohmmeter)
• Microwave survey meter
• Microwave survey meter
- Holaday HI-1500
HI-1501
- Narda 8100
8200
• Inch scale
• 600 cc non conductive material beaker (glass or
• 600 cc non conductive material beaker (glass or
plastic), inside diameter: approx. 8.5 cm(3
1
/2
in.)
• Cylindrical and made of borosilicate glass vessel.
max. thickness: 3 mm
outside diameter: approx. 190mm
height: approx. 90mm
outside diameter: approx. 190mm
height: approx. 90mm
• Glass thermometer: 100°C or 212°F (1 deg scale)
MEASURING MICROWAVE ENERGY
LEAKAGE
LEAKAGE
• Pour 275±15cc of 20±5°C(68±9°F) water in a beaker
which is graduated to 600 cc, and place the beaker
on the center of the turntable.
on the center of the turntable.
• Set the energy leakage monitor to 2,450 MHz and
use it following the manufacturer's recommended
test procedure to assure correct result.
test procedure to assure correct result.
• When measuring the leakage, always use the 2-inch
(5cm) spacer supplied with the probe.
• Operate the oven at its maximum output.
• Measure the microwave radiation using and
• Measure the microwave radiation using and
electromagnetic radiation monitor by holding the
probe perpendicular to the surface being measured
probe perpendicular to the surface being measured
Move probe along shaded area
Probe scanning speed
Less than 2.5 cm/sec
( 1in/sec)
Less than 2.5 cm/sec
( 1in/sec)
5-1
SERVICE INFORMATION
TOOLS AND MEASURING INSTRUMENTS
MICROWAVE LEAKAGE TEST
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