LG MS-0742SG Manual de usuario
P/NO : 3828W5S4049 April, 2004
Printed in Korea
MIC OWAVE OVEN
SERVICE MANUAL
MODEL: MS-0742SG
CAUTION
BEFO E SE VICING THE UNIT, EAD THE
SAFETY P ECAUTIONS IN THIS MANUAL.
website http://bi .lgservice.com
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
FEATU ES
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4-1
CONT OL PANEL
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4-1
OPE ATING SEQUENCE
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4-2
SCHEMATIC DIAG AM
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4-3
CI CUIT DESC IPTION
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4-4
SERVICE INFORMATION
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5-1
TOOLS AND MEASU ING INST UMENTS
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5-1
MIC OWAVE LEAKAGE TEST
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5-1
MEASU EMENT OF MIC OWAVE POWE OUTPUT
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5-3
DISASSEMBLY AND ADJUSTMENT
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5-3
INTE LOCK CONTINUITY TEST
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5-7
COMPONENT TEST P OCEDU E
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5-8
T OUBLE SHOOTING
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5-11
EXPLODED VIEW
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6-1
REPLACEMENT PARTS LIST
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7-1
SCHEMATIC DIAGRAM OF P.C.B.
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8-1
P INTED CI CUIT BOA D
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8-2
P.C.B. PARTS LIST
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9-1
CONTENTS
This microwave oven is designed for household use only.
It is not recommended for commercial purposes.
ITEM
MODEL
Power equirement
Power Output
Microwave Frequency
Magnetron
Timer
Outside Dimensions
Cavity Dimensions
Net Weight
Shipping weight
Control Complement
Nameplate Location
Accessories
DESCRIPTION
MS-0742SG
120 Volts AC 60 Hz
1,000 Watts (8.5A)
Single phase, 3 wire grounded
700 Watts full microwave power (IEC60705)
2,450 MHz
2M213-240GP
0 ~ 99 min. 99 sec.
455 (W) x 284 (H) x 320 (D)
327 (W) x 202 (H) x 286 (D)
11.2 kg (approx.)
12.2 kg (approx.)
Touch Control System
Clock : 1:00 - 12:59
Microwave Power for Variable Cooking
Power level
HIGH ------------------------------------------ Full power throughout the cooking time
9 (Saute)--------- approx. 90% of Full power, 8 ( eheat)------------- approx. 80%
7 (Med.-High)--------------------- approx. 70%, 6 (Medium)------------ approx. 60%
5 (Med.-Low) --------------------- approx. 50%, 4 (Defrost)------------- approx. 40%
3 (Low)----------------------------- approx. 30%, 2 (Simmer) ------------ approx. 20%
1 (Warm)--------------------------- approx. 10%
Owner's manual
Glass turntable
Back Side
1-1
SPECIFICATIONS
• DO NOT operate on a 2-wire extension cord during
repair and use.
• NEVER TOUCH any o en components or wiring during
operation.
• BEFORE TOUCHING any parts of the o en, always
remo e the power plug from the outlet.
• For about 30 seconds after the o en stops, an electric
charge remains in the high oltage capacitor. When
replacing or checking, you must discharge the high
oltage capacitor by shorting across the two terminals
with an insulated screwdri er.
•
Remo e your watches whene er working close to or
replacing the Magnetron.
• DO NOT touch any parts of the control panel circuit. A
resulting static electric discharge may damage this
P.C.B.
• NEVER operate the o en with no load.
• NEVER injure the door seal and front plate of the o en
ca ity.
• NEVER put iron tools on the magnetron.
• NEVER put anything into the latch hole and the
interlock switches area.
• Proper operation of the microwa e o en requires that
the magnetron be assembled to the wa eguide and
ca ity. Ne er 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 microwa e o en is
high- oltage and high-current equipment.
Though it is free from danger in ordinary use,
extreme care should be taken during repair.
THE OVEN S TO BE SERV CED ONLY
BY PROPERLY QUAL F ED SERV CE
PERSONNEL.
M CROWAVE RAD AT ON
Personnel should not be exposed to the
microwa e energy which may radiate from the
magnetron or other microwa e generating
de ice if it is improperly used or connection.
All input and output microwa e connections,
wa eguide, flange, and gasket must be secure
ne er operate the de ice without a microwa e
energy absorbing load attached.
Ne er look into an open wa eguide or antenna
while the de ice is energized.
Gasket
ANTENNA
COOLING FIN
MAGNETRON
CHASSIS GROUND
FILAMENT
TERMINALS
MAGNETRON
INSTALLATIONS
3-1
NSTALL NG
1. Empty the microwa e o en and clean inside it with
a soft, damp cloth. Check for damage such as
misaligned door, damage around the door or dents
inside the ca ity or on the exterior.
2. Put the o en on a counter, table, or shelf that is
strong enough to hold the o en and the food and
utensils you put in it. (The control panel side of the
o en is the hea y side. Use care when handling.)
3. Do not block the ent and the air intake openings.
Blocking ent or air intake openings can cause
damage to the o en and poor cooking results.
Make sure the microwa e o en legs are in place to
ensure proper air flow.
4. The o en 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 o en next to a con entional
surface unit or abo e a con entional wall o en.
5. Use microwa e o en in an ambient temperature
less than 104°F(40°C).
6. Place the microwa e o en on a sturdy and flat
surface at least 10 cm(4 inches) from the wall.
7. Place the microwa e o en as far away as possible
from TV, RADIO, COMPUTER, etc., to pre ent
interference.
GROUND NG NSTRUCT ONS
For personal safety, this appliance must be fully
grounded at all times.
In the e ent 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 BEG N, READ THE FOLLOW NG NSTRUCT ONS COMPLETELY AND CAREFULLY.
10cm
WARN NG
Improper use of the grounding plug can result in a
risk of electric shock.
Do not, under any circumstances, cut or remo e
the third ground prong from the power cord plug.
PREFERRED METHOD
INSURE PROPER GROUND
EXISTS BEFORE USE
FEATURES
CONTROL PANEL
1. INDICATORS
2. ONE TOUCH CONTROL: Used to cook the foods
listed by one touch.
3. CLOCK: Used to set the time of day.
4. AUTO DEFROST: Used to select the desired auto
weight defrost programmed with weight pad.
5. TIME: Used to cook food for a desired time.
6. NUMBER: Used to set for time of day, cooking time,
power level or defrost weight.
7. POWER: Used to select the desired power level for
cooking.
8. STOP/CLEAR: Used to stop oven and clear all
entries except time of day.
. START: One tap allows oven to begin functioning.
10. QUICK START
4-1
OPERATING INSTRUCTIONS
Oven ront Plate
Window Door Screen
Door Seal
Display Window
Control Panel
Safety Door Lock System
Turntable
Roller Rest
3
5
7
10
2
4
6
8
9
1
OPERATING SEQUENCE
The following is a description of component functions
during oven operation.
1. SETTING THE CLOCK
ex.) To set 4:30, touch number ke [4],[3], and [0].
NOTE: 1) This is a 12 hour clock.
2) Clock will operate as long as power is
applied to the oven.
2. CANCEL FUNCTION
Touch the pad whenever ou need to
cancel an entr or a function currentl in use.
The displa will either return to the last item entered
or to the clock.
3. Ez On
4. ONE TOUCH COOKING
NOTE: Heat onl 1 package at a time
5. TIME COOKING
6. MULTI-STAGE COOKING
7. AUTO DEFROST COOKING
8. CHILD LOCK
This oven has a CHILD LOCK feature
TO SET CHILD LOCK
• Touch the pad
• Touch and hold 0 pad L appear on
the displa .
TO CANCEL CHILD LOCK
• Touch the pad
• touch and hold 0 pad L disappear.
STOP/CLEAR CLOCK NUMBER
STOP/CLEAR POPCORN
STOP/CLEAR Ez On
STOP/CLEAR
1ST STAGE
1ST STAGE
CLOCK
STOP/CLEAR AUTO
DEFROST NUMBER OF
WEIGHT START
STOP/CLEAR TIME NUMBER POWER
NUMBER START
STOP/CLEAR TIME NUMBER POWER
NUMBER
2ND STAGE
TIME NUMBER POWER
NUMBER START
0
0
4-2
SCHEMATIC DIAGRAM
4-3
IMPORTANT SAFETY NOTE: THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES
IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION, FIRE, ELECTRICAL SHOCK, AND
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 BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND
SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.
CIRCUIT DESCRIPTION
GENERAL DETAILS
• The low voltage transformer supplies the necessary
voltage to the micom controller when power cord is
plugged in.
• When the door is closed, the primary switch is ON, the
secondary switch is ON, and the monitor switch opens
(contact COM and NO .
WHEN SELECTING COOKING POWER
LEVEL AND TIME
• The micom controller memorizes the function you set.
• The time you set appears in the display window.
• Each indicator light turns on to indicate that the stage
has been set.
WHEN TOUCHING THE START PAD
• The coil of the relay is energized by the micom
controller.
• Power input is supplied to the high voltage transformer
through the fuse to the primary switch and relay 2.
• 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 OVEN IS SET AT ANY LEVEL
EXCEPT MAXIMUM.
• The micom controller controls the ON-OFF time of
relay 2 by the applied signal to vary the average output
power of microwave oven as POWER LEVEL.
(refer to page 1-1
• One complete cycle of relay 2 is 22 seconds.
WHEN THE DOOR IS OPENED DURING
COOKING
• Both the primary switch and relay 2 cut off the primary
winding voltage of the high voltage transformer.
• ON-OFF of relay 2 is coupled electrically with opening
and closing of the secondary switch.
• When the door is opened, the secondary switch is
opened and when the door is closed, the secondary
switch is closed.
• The cooking time stops counting down.
• Relay stops functioning.
• As the door is opened, if the contact of primary switch
and relay2 and/or secondary 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.
4-4
FUSE
H.V.
TRANS-
FORMER
RELAY 2
MICOM CONTROLLER
SECONDARY
SWITCH
MONITOR
SWITCH
N
PRIMARY
SWITCH
L
FUSE
H.V.
TRANS-
FORMER
RELAY 2
MICOM CONTROLLER
SECONDARY
SWITCH
MONITOR
SWITCH
N
PRIMARY
SWITCH
L
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