LG MA-6400xx Service Manual
MICROW AVE OVEN
SER VICE MANUAL
MODEL: MA-6400W2
MA-6400B2
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
website: http://www.lgservice.com
e-mail: http://www.lgeservice.com/techsup.html
This device is to be serviced only by properly qualified service personnel.
Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be
taken to avoid possible exposure to excessive microwave energy.
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
A) Do not operate or allow the oven to be operated with the door open.
B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other
microwave source, and make repairs as necessary; (1) interlock operation, (2) proper door closing, (3)
seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and
latches, (5) evidence of dropping or abuse.
C) Before turning on microwave power for any service test or inspection within the microwave generating
compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,
integrity, and connections.
D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation
and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual
before the oven is released to the owner.
E) A microwave leakage check to verify compliance with the Federal Performance Standard should be
performed on each oven prior to release to the owner.
SAFETY PRECAUTIONS
(Page)
SAFETY PRECAUTIONS
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Inside front cover
SPECIFICATIONS
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1-1
CAUTIONS
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2-1
INSTALLATIONS
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3-1
OPERATING INSTRUCTIONS
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4-1
FEATURES
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4-1
CONTROL PANEL
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4-1
OPERATING SEQUENCE
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4-2
SCHEMATIC DIAGRAM
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4-3
CIRCUIT DESCRIPTION
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4-4
SERVICE INFORMATION
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5-1
TOOLS AND MEASURING INSTRUMENTS
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5-1
MICROWAVE LEAKAGE TEST
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5-1
MEASUREMENT OF MICROWAVE POWER OUTPUT
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5-3
DISASSEMBLY AND ADJUSTMENT
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5-3
INTERLOCK CONTINUITY TEST
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5-7
COMPONENT TEST PROCEDURE
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5-8
TROUBLE SHOOTING
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5-11
EXPLODED VIEW
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6-1
REPLACEMENT PARTS LIST
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7-1
CONTENTS
1-1
SPECIFICATIONS
This microwave oven is designed for household use only.
It is not recommended for commercial purposes.
ITEM
MODEL
Power Requirement
Power Output
Microwave Frequency
Magnetron
Timer
Outside Dimensions
Cavity Dimensions
Net Weight
Shipping weight
Control Complement
Nameplate Location
Accessories
DESCRIPTION
MA-6400W2/MA-6400B2
120 Volts AC 60 Hz
910 Watts (8.5A)
Single phase, 3 wire grounded
600 Watts full microwave power (IEC60705)
2,450 MHz
2M213-09B
0 ~ 30 min.
19” (W) x 11” (H) x 12 7/8” (D)
11 7/8
” (W) x 7
5
/8
” (H) x 12
1
/2
” (D)
24.7 lbs (approx.)
26.9 lbs (approx.)
Mechanical Rotary System
Full Power Cooking
Owner's manual & cooking guide
Glass turntable
Rotating Ring
Back Side
• DO NOT operate on a 2-wire extension cord during
repair and use.
• NEVER TOUCH any oven components or wiring during
operation.
• BEFORE TOUCHING any parts of the oven, always
remove the power plug from the outlet.
• For about 30 seconds after the oven stops, an electric
charge remains in the high voltage capacitor. When
replacing or checking, you must discharge the high
voltage capacitor by shorting across the two terminals
with an insulated screwdriver.
•
Remove your watches whenever working close to or
replacing the Magnetron.
• NEVER operate the oven with no load.
• NEVER injure the door seal and front plate of the oven
cavity.
• NEVER put iron tools on the magnetron.
• NEVER put anything into the latch hole and the
interlock switches area.
• Proper operation of the microwave oven requires that
the magnetron be assembled to the waveguide and
cavity. Never operate the magnetron unless it is
properly installed.
• Be sure that the magnetron gasket is properly
installed around the dome of the tube whenever
installing the magnetron.
2-1
CAUTIONS
Unlike other appliances, the microwave oven is
high-voltage and high-current equipment.
Though it is free from danger in ordinary use,
extreme care should be taken during repair.
THE OVEN IS TO BE SERVICED ONLY
BY PROPERLY QUALIFIED SERVICE
PERSONNEL.
MICROWAVE RADIATION
Personnel should not be exposed to the
microwave energy which may radiate from the
magnetron or other microwave generating
device if it is improperly used or connection.
All input and output microwave connections,
waveguide, flange, and gasket must be secure
never operate the device without a microwave
energy absorbing load attached.
Never look into an open waveguide or antenna
while the device is energized.
Gasket
ANTENNA
COOLING FIN
MAGNETRON
CHASSIS GROUND
FILAMENT
TERMINALS
MAGNETRON
INSTALLATIONS
3-1
INSTALLING
1. Empty the microwave oven and clean inside it with
a soft, damp cloth. Check for damage such as
misaligned door, damage around the door or dents
inside the cavity or on the exterior.
2. Put the oven on a counter, table, or shelf that is
strong enough to hold the oven and the food and
utensils you put in it. (The control panel side of the
oven is the heavy side. Use care when handling.)
3. Do not block the vent and the air intake openings.
Blocking vent or air intake openings can cause
damage to the oven and poor cooking results.
Make sure the microwave oven legs are in place to
ensure proper air flow.
4. The oven should not be installed in any area where
heat and steam are generated, because they may
damage the electronic or mechanical parts of the
unit.
Do not install the oven next to a conventional
surface unit or above a conventional wall oven.
5. Use microwave oven in an ambient temperature
less than 104°F(40°C).
6. Place the microwave oven on a sturdy and flat
surface at least 10 cm(4 inches) from the wall.
7. Place the microwave oven as far away as possible
from TV, RADIO, COMPUTER, etc., to prevent
interference.
GROUNDING INSTRUCTIONS
For personal safety, this appliance must be fully
grounded at all times.
In the event of an electrical short circuit, grounding
reduces the risk of electrical shock.
The plug must be plugged into an outlet that is
properly installed and grounded.
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
WARNING
Improper use of the grounding plug can result in a
risk of electric shock.
Do not, under any circumstances, cut or remove
the third ground prong from the power cord plug.
PREFERRED METHOD
ENSURE PROPER GROUND
EXISTS BEFORE USE
10cm
4-1
OPERATING INSTRUCTIONS
FEATURES
Oven Front Plate
Window Door Screen
Door Seal
Power Knob
Door Open Button
Safety Door Lock System
Turntable
Rotating Ring
Timer Knob
min
DEFROST
COOK
The microwave oven is designed to be simple and
easy to operate. Please follow these instructions
carefully.
1. Place the food in a suitable cooking utensil. Open
the microwave oven door and place the utensil in
the center of the oven on the glass tray.
2. Close the oven door.
3. Turn the TIMER KNOB clockwise to set the
cooking time.
4. When the TIMER reaches OFF, the signal sounds
and the oven will automatically shut off.
5. Open the door and remove the food from the
oven.
6. To stop cooking before the timer reaches OFF,
either open the door or simply turn the timer to
OFF.
NOTE :
1. The oven starts as soon as the KNOB is turned.
We recommend turning the KNOB past the time
you want and then turn back to the desired setting.
2. The door can be opened during the cooking
process by pushing the Door Open Button. The
timer will stop and the microwave activity will
cease. When the door is closed, cooking will
resume until the full cooking time has elapsed.
After cooking is finished, the Timer will be at OFF.
After unpacking this appliance, examine the new
oven for evidence of shipping damage. This is most
important since a damaged oven may allow the
escape of microwave energy. Make sure you remove
all packing from the microwave cavity.
Check the oven operation when unpacking the unit
and any time the oven is not working properly.
1. Plug the power cord into an earthed electrical
socket.
2. Place the glass tray inside the oven cavity.
3. Place a cup of water (at room temperature) inside
the oven, on the glass tray.
4. Close the door securely.
5. Set the Timer for 3 to 4 minutes (note : microwave
activity starts).
6. When the cooking time has elapsed, the signal will
sound (note: all microwave activity stops).
7. If the oven is operating normally, the water will be
hot.
OPERATION CHECK
OPERATING PROCEDURE
SCHEMATIC DIAGRAM
4-2
** NOTE : DOOR IS OPENED.
BK : BLACK N BL : BLUE BN : BROWN
RD : RED WH : WHITE GN: GREEN
L
L
N
GN
BN
BL
BL
BL
WH
WH
OVEN
THERMOSTAT
SECONDARY
SWITCH
WH
MONITOR
SWITCH
OVEN
LAMP
FAN
MOTOR
TURN
TABLE
MOTOR
TIMER
MOTOR
BK BK
BK
BK
4
3
RDRD
RD
RD
RD
WH
T.MF.M T.T.MO.L
H.V DIODE
MAGNETRON
CHOKE FILTER(optional)
1
2
FUSE
15A
PRIMARY
SWITCH
TIMER
SWITCH
H.V
TRANSFORMER
H.V
CAPACITOR
N
AC 120V
60Hz
IMPORTANT SAFETY NOTE: THE COMPONENTS IN SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES
IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION, FIRE, NELECTRICAL SHOCK, AND OTHER
HAZARDS. WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER'S SPECIFIED PARTS
BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAGRAM.
NOTICE: SINCE THIS IS A BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND
SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.
CIRCUIT DESCRIPTION
GENERAL DETAILS
• When the door is closed, the primary switch is ON, the
secondary switch is ON, and the monitor switch opens
(contact COM and NO).
• The latches are secured by the latch board, the oven
light turns on while the oven is operation.
WHEN THE TIMER KNOB IS ROTATED
• When the timer knob is rotated, the contacts of timer
switch close.
• The contact of the secondary switch close the circuit.
• Power input is supplied to the high voltage transformer
through the fuse to the primary timer and secondary
switches.
• Turntable rotates
• The fan motor rotates and cools the magnetron by
blowing the air (coming from the intake on the
baseplate).
• The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.
• Cooking time starts counting down.
• 3.2 volts AC is generated from the filament winding of
the high voltage transformer. This 3.2 volts is applied to
the magnetron to heat the magnetron filament through
two noise-preventing choke coils.
• A high voltage of approximately 2100 volts AC is
generated in the secondary of the high voltage
transformer which is increased by the action of the high
voltage diode and charging of the high voltage
capacitor.
• The negative 4,000 Volts DC is applied to the filament
of the magnetron.
WHEN THE DOOR IS OPENED DURING
COOKING
• Both the primary and timer switches are cut off primary
winding voltage of the high voltage transformer.
• When the door is opened, the secondary switch is
opened and when the door is closed, the secondary
switch is closed.
• The timer, turntable and fan motor stop.
• As the door is opened, if the contact of primary switch
fail to open, the fuse opens due to the large current
surge caused by the monitor switch activation, which in
turn stops magnetron oscillation.
4-3
FUSE
P/S
P/S : Primary Switch
T/S : Timer Switch
S/S : Secondary Switch
T/S S/S
H.V.
TRANS-
FORMER
FUSE
P/S
T/S S/S
M/S
P/S : Primary Switch
T/S : Timer Switch
M/S : Monitor Switch
S/S : Secondary Switch
H.V.
TRANS-
FORMER
CAUTIONS
• Be sure to check microwave leakage prior to
servicing the oven if the oven is operative prior to
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/cm2and 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.
• If the oven operates with the door open, the service
personnel should:
- Tell the user not to operate the oven.
- Contact the manufacturer and CDRH
(Center for Devices and Radiological Health)
immediately.
NOTE: Address on CDRH
Office of Compliance(HFZ-312)
Center for Devices and Radiological
Healthe 1390, Piccard Drive,
Rockville. MD 20850
• 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
4 mW/cm2. Always start measuring of an unknown field
to assure safety for operating personnel from radiation
leakage.
MEASURING MICROWAVE ENERGY
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.
• Set the energy leakage monitor to 2,450 MHz and
use it following the manufacturer's recommended
test procedure to assure correct result.
• When measuring the leakage, always use the 2inch (5cm) spacer supplied with the probe.
• Operate the oven at its maximum output.
• Measure the microwave radiation using and
electromagnetic radiation monitor by holding the
probe perpendicular to the surface being measured
Move probe along shaded area
Probe scanning speed
Less than 2.5 cm/sec
( 1in/sec)
5-1
SERVICE INFORMATION
TOOLS AND MEASURING INSTRUMENTS
MICROWAVE LEAKAGE TEST
NECESSARY TOOLS
Tools normally used for TV servicing are sufficient.
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
NECESSARY MEASURING INSTRUMENTS
• TESTER (VOLTS-DC, AC, Ohmmeter)
• Microwave survey meter
- Holaday HI-1500
HI-1501
- Narda 8100
8200
• Inch scale
• 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
• Glass thermometer: 100°C or 212°F (1 deg scale)
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