LG 3828W5S1802 Service Manual

MICROW AVE OVEN
SER VICE MANUAL
MODEL: MS-114YF/MS-114YB
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : 3828W5S1802
March, 2001
Website http://biz.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.
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
SCHEMATIC DIAGRAM OF P.C.B.
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8-1
PRINTED CIRCUIT BOARD
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8-2
P.C.B. PARTS LIST
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9-1
CONTENTS
1-1
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
MS-114YF/MS-114YB
120 Volts AC 60 Hz 1,550 Watts Single phase, 3 wire grounded 1,150 Watts full microwave power (IEC60705) 2,450 MHz 2M246, 2M248J 0 ~ 99 min. 99 sec. 530 (W) x 315 (H) x 394 (D) 348 (W) x 242 (H) x 373 (D) 15 kg (approx.) 17 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 (Reheat) --------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 & cooking guide Glass turntable Rotating ring
Back Side
SPECIFICATIONS
• 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.
• DO NOT touch any parts of the control panel circuit. A resulting static electric discharge may damage this P.C.B.
• 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
FEATURES
CONTROL PANEL
1. INDICATORS.
2. LOCAL MENU: This menu has been preprogrammed to
cook food automatically by one touch.
3. AUTO COOK: This feature provides you with the best cooking method by selecting menu.
4. LIGHT MENU: This menu has been preprogrammed to cook food automatically.
5. QUICK DEFROST: This feature provides you with the quick defrosting method for 0.5kg of beef.
6. HOLD WARM: You can keep the food warming by this key.
7. NUMBER: These used to set for time of day, cooking time &
power level, or defrost weight.
8. START: This feature allows oven to begin functioning.
9. AUTO REHEAT: This menu has been preprogrammed to
reheat food automatically by selecting menu.
10. AUTO DEFROST: This feature provides you with the best
defrosting method for frozen foods.
11. MICRO: This feature is used for manual cooking or 2 stage
cooking.
12. OPTION: You can select sound ON/OFF, demo ON/OFF
and scroll speed.
13. POWER: You can select the desired power level for
cooking.
14. CLOCK: It is used to set the time of day.
15. STOP/CLEAR: It used to stop oven and clear all entries
except time of day.
16. ADD 30 MINUTES.
4-1
OPERATING INSTRUCTIONS
OVEN CAVITY
DISPLAY WINDOW
DOOR SEAL
CONTROL PANEL
GLASS TURNTABLE
ROTATING RING
SAFETY INTERLOCK
SYSTEM
1
2
3 4
5 6
9 10
11 12
13
7
14
8
15 16
4-2
OPERATING SEQUENCE
The following is a description of component functions during oven operation.
1. SETTING THE CLOCK
ex.) To set 4:30, touch number key [4],[3], and [0].
NOTE: 1) Clock will operate as long as power is
applied to the oven.
2. CANCEL FUNCTION
Touch the pad whenever you need to cancel an entry or a function currently in use. The display will either return to the last item entered or to the clock.
3. QUICK START
4. ONE TOUCH COOKING
5. TIME COOKING
6. MULTI-STAGE COOKING
7. AUTO WEIGHT DEFROST COOKING
8. CHILD LOCK
This oven has a CHILD LOCK feature
TO SET CHILD LOCK
Touch the pad
Touch and hold
PARAR/BORRAR
pad
BLOQUEADO
appear on the display.
TO CANCEL CHILD LOCK
Touch the pad
Touch and hold
PARAR/BORRAR
pad
DESBLOQUEADO disappears.
9. OPTION
You can select ON/OFF of beeper, ON/OFF of demo and scroll speed.
To select sound ON/OFF
To select scroll speed.
To select demo ON/OFF.
PARAR/BORRAR
FRIJOLES
PARAR/BORRAR
+30 MÁS
PARAR/BORRAR
1ST STAGE
INICIO
PARAR/BORRAR
DESCONGELADO
AUTO.
NUMBER OF
WEIGHT
INICIO
PARAR/BORRAR
OPCIÓN
INICIO
PARAR/BORRAR
OPCIÓN OPCIÓN
NUMBER
INICIO
PARAR/BORRAR
OPCIÓN OPCIÓN OPCIÓN
INICIO
PARAR/BORRAR
MICRO
NUMBER
POTENCIA
NUMBER INICIO
PARAR/BORRAR
MICRO
NUMBER
POTENCIA
NUMBER
MICRO
NUMBER
INICIO
POTENCIA
NUMBER
2ND STAGE
PARAR/BORRAR
PARAR/BORRAR
PARAR/BORRAR RELOJ
NUMBER
SCHEMATIC DIAGRAM
4-3
RD
RD
BK
PRIMARY
SWITCH
WH
WH
WH
WH
YL
MAGNETRON
RD
H.V.
CAPACITOR
H.V. DIODE
FUSE
20A
AC 220V
50Hz
BL
L
N
MICOM
CONTROLLER
F.M.
TRANSFORMER
H.V.
** NOTE : DOOR IS OPENED.
BK : BLACK BL : BLUE YL : YELLOW RD : RED
WH : WHITE PK : PINK GN : GREEN BN : BROWN
T.T.M.
O.L.
CN1
PT1
1
2
3
4
5
6
7
8
BK
BK
GN
GN
PK
BN
SECONDARY
SWITCH
OVEN
LAMP
MONITOR
SWITCH
TURN
TABLE
MOTOR
FAN
MOTOR
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.
RY1
RY2
GN
WH
BK
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.
3.3 volts AC is generated from the filament winding of
the high voltage transformer. This 3.3 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
L
FUSE
H.V.
TRANS-
FORMER
RELAY 2
MICOM CONTROLLER
SECONDARY SWITCH
PRIMARY
SWITCH
MONITOR
SWITCH
N
L
N
FUSE
PRIMARY
SWITCH
RELAY 2
MICOM CONTROLLER
MONITOR
SWITCH
H.V.
TRANS-
FORMER
SECONDARY SWITCH
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.
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 2-inch (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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