LG JVM1790WK, JVM1790SK, JVM1790CK, JVM1790BK Service Manual
삼 흥
정 판
Microwave Oven
Service Manual
JVM1790BK/CK/SK/WK
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.
CAUTION
SAFETY PRECAUTIONS
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.
• Proper operation of the microwave ovens requires that the magnetron be assembled to the
wave guide 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.
• Routine service safety procedures should be exercised at all times.
• Untrained personnel should not attempt service without a thorough review of the test
procedures and safety information contained in this manual.
FOREWORD
Read this Manual carefully. Failure to adhere to or observe the information in this Manual may result in exposing
yourself to the Microwave Energy normally contained within the oven cavity.
TABLE OF CONTENTS
(Page)
SAFETY PRECAUTIONS
SPECIFICATIONS
CAUTIONS
INSTALLATIONS
OPERATING INSTRUCTIONS
CONTROL PANEL
CONTROL PANEL INSTRUCTIONS
OVERALL CIRCUIT DIAGRAM
SCHEMATIC DIAGRAM
MATRIX CIRCUIT FOR TOUCH KEY BOARD
GENERAL INFORMATION FOR SERVICE
GENERAL PRECAUTIONS IN USE
TRIAL OPERATION
FEATURES AND SPECIFICATIONS FEATURES
SERVICE INFORMATION
PRECAUTIONS AND REPAIR SERVICE TIPS
MICROWAVE LEAKAGE TEST
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Inside front page
1-1
2-1
3-1
4-1
4-1
4-2
5-1
5-1
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5-2
6-1
6-1
6-1
6-1
7-1
7-1
7-2
POWER OUTPUT MEASUREMENT
DISASSEMBLY INSTRUCTIONS
INTERLOCK SYSTEM
INTERLOCK CONTINUITY TEST
TEST AND CHECKOUT PROCEDURES AND TROUBLE SHOOTING
A. TEST PROCEDURES
B. CHECKOUT PROCEDURES
C. TROUBLE SHOOTING
EXPLODED VIEW
PART REFERENCE LIST
SCHEMATIC DIAGRAM OF PCB
PRINTED CIRCUIT BOARD
PCB PARTS LIST
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7-3
7-4
7-12
7-14
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7-15
7-15
7-19
7-24
8-1
9-1
10-1
10-2
11-1
SPECIFICATIONS
Rated Power Consumption
Microwave Output
Frequency
Power Supply
Rated Current
Magnetron Cooling
Rectification
Door Sealing
Safety Devices
Magnetron
High Voltage Capacitor
High Voltage Diode
Cook top Lamp
Cavity Lamp
Timer
Tray
Overall Dimensions
Effective Capacity of Oven Cavity
Accessories
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1600W (Microwave oven only) 1650W (Convection only)
1000W (IEC60705)
Adjustable 100W through 1000W, 10 steps
2450 MHz ± 50 MHz
120 VAC, 60 Hz
13.5 Amp. (Microwave oven+Cook top lamp+Ventilation fan)
Forced Air Cooling
Rectification Voltage Double Half-Wave
Choke System
Magnetron Thermal Fuse:
Open at 150°C ± 6°C
Oven Cavity Thermostat:
Open at 145°C ± 6°C
Fuse(20A)
Primary Interlock Switch
Secondary Interlock Switch
Interlock Monitor
2M246-21CT
Capacitor: 0.95µF, 2.1 KV AC
Diode; 350mA, 9.0 KV
130 V, 50 W
130 V, 35 W
Digital, up to 95 mim. 00 sec. (in each cooking stage)
Tempered Safety Glass
2915/16"(W)x167/16"(H)x153/8"(D)
1.7 Cu.ft.
Owner’s Manual & Cooking Guide, Installation Manual,
Exhaust Adapter, Exhaust Damper, Mounting Kit and Two
Filters, Rotating Ring Assembly, Metal Racks.
1-1
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.
• 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.
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.
• 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.
• 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.
ANTENNA
Gasket
COOLING FIN
FILAMENT
TERMINALS
MAGNETRON
CHASSIS GROUND
MAGNETRON
THE OVEN IS TO BE SERVICED ONLY
BY PROPERLY QUALIFIED SERVICE
PERSONNEL.
2-1
INSTALLATIONS
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
PRECAUTIONS ON INSTALLATION
A. Plug the power supply cord into a 120V AC, 60Hz,
single-phase power source with a capacity of 15A
or 20A.
B. Avoid placing the unit in a location where there is
direct heat or splashing water.
C. Install the unit on the mounting plate firmly.
D. Place the unit as far away as possible from TV,
radio, 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.
CAUTION
This unit is equipped with a 3-prong plug for your
safety. If the wall outlet is a grounded 3-hole type,
the unit will be grounded automatically.
Plug with Ground
Prong
Properly Polarized
and Grounded
Outlet
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.
3-1
CONTROL PANEL
OPERATING INSTRUCTIONS
For Model: JVM1790BK
JVM1790CK
JVM1790SK
JVM1790WK
4-1
CONTROL PANEL INSTRUCTIONS
1. TIME COOK: Touch this pad when setting Microwave
cooking.
2. CONVECTION BAKE: Touch this pad when setting
Convection bake cooking.
3. CONVECTION ROAST: Touch this pad when setting
Convection roast cooking.
4. COMBINATION FAST BAKE: Touch this pad when setting
Combination cooking.
5. POPCORN: Touch this pad when popping
popcorn in your microwave oven. The oven’s sensor
will tell the oven how long to cook depending on the
amount of humidity it detects from the popcorn.
6. AUTO COOK: Touch this pad to cook chicken pieces, fish,
ground meat, potatoes, canned vegetables, fresh
vegetables, frozen vegetables. The oven’s
sensor will tell the oven how long to cook depending
on the amount of humidity coming from the food.
7. REHEAT: Touch this pad to reheat leftovers.
The oven’s sensor will tell the oven how long to
cook depending on the amount of humidity coming
from the food.
8. WARM: Touch this pad to warm.
10. TIMER: Touch this pad to set the timer.
11. CLOCK AM/FM: Touch this pad to enter the time of day.
12. OPTION: Touch this pad to change the oven’s default
settings.
13. POWER: Touch this pad to select a cooking power
level.
14. CLEAR/OFF: Touch this pad to stop the oven or
to clear all entries.
15. START/PAUSE: Touch this pad to start a function
or enter all entries. If you open the door after oven
begins to cook, touch START/PAUSE again.
16. TURNTABLE ON/OFF: Touch this pad to turn off
the turntable. OFF will appear in the display.
17. SURFACE LIGHT: Touch this pad to turn on the
cooktop/countertop light.
18. VENT FAN: Touch this pad to turn the fan
on/off.
9. DEFROST: Touch this pad to select food
type and defrost food by weight.
4-2
OVERALL CIRCUIT DIAGRAM
ERROR MODEDISPLAY
F1
F2
F3
F4
F5
THERMAL SENSOR OPEN
THERMAL SENSOR SHORT
KEYPANEL SHORTED FOR > 60 SECONDS
HUMIDITY SENSOR OPEN
HUMIDITY SENSOR SHORT
SCHEMATIC DIAGRAM
For Model: JVM1790BK
JVM1790CK
JVM1790SK
JVM1790WK
5-1
MATRIX CIRCUIT FOR TOUCH KEY BOARD
For Model: JVM1790BK / JVM1790CK
JVM1790SK / JVM1790WK
5-2
GENERAL INFORMATION FOR SERVICE
GENERAL PRECAUTIONS IN USE
A. Never operate the unit when it is empty.
Operating the oven with no load may shorten the
life of the magnetron. Whenever cooking dry foods
(dried fish, bread, etc.) or a small amount of food,
be sure to put a glass of water into the cooking
compartment. The glass turntable may become hot
after operating, be careful when touching it.
B. Aluminum foil should be avoided because it will
disrupt cooking and may cause arcing. However,
small pieces may be used to cover some parts of
food to slow the cooking. Any aluminum foil used
should never be closer than 2.5 cm to any side wall
of the oven.
TRIAL OPERATION
After installation, the following sequences and results
should be checked carefully.
A. Put a container filled with water (about 1 liter) into
the oven, and close the door tightly.
B. Set cooking time for 10 minutes by touching “1”
and then “0” three times. “1, 0, 0, 0” appears in
the display window.
C. Touch the START key.
Make sure the cavity light comes on. The unit will
begin cooking and the display window will show the
time counting down by seconds.
D. After about 5 minutes, make sure the primary
interlock switch, the secondary interlock switch and
the interlock monitor switch operate properly by
opening and closing the door several times. Touch
the START key each time the door is closed.
E. Continue operating the unit. Four long beep sound
signal is heard when the time is up. The unit will
shut off automatically.
F. Confirm the water is hot.
G. Finally, measure the output power according to
“POWER OUTPUT MEASUREMENT” on
page 7-3.
FEATURES AND SPECIFICATIONS
FEATURES
A. The safety systems incorporated in this model are:
(1) Primary interlock switch
(2) Secondary interlock switch
(3) Interlock monitor switch
(4) Choke system
(5) Magnetron thermostat
(6) Oven cavity thermostat
(Note: This thermostat located on the oven
cavity will open and stop the unit from operation
only if a high temperature is reached, such as,
a fire created by overcooking food.)
B. Any one of 10 power output levels ranging 100W to
1000W can be selected by the touch control and
electronic computer system.
STANDARD TEST LOAD
The standard test load is one liter (1000ml.) water with
starting temperature of 59°F ~ 75°F in a 1000ml
beaker.
(DO NOT USE ANY OTHER LOAD OR DISH AS
RESULTS WILL VARY FROM STANDARD.)
PERFORMANCE TEST FOR MICROWAVE
1. Use Glass Tray and the beaker WB64 x 0073.
2. Record initial water temperature.
3. Run at high power for 2:03.
4. Record end water temperature.
The minimum difference between the initial and
ending temperature should be: 38°F @ 120V
TO PREVENT ELECTRICAL SHOCK. USE EXTREME
CAUTION WHEN DIAGNOSING OVEN WITH OUTER
CASE REMOVED AND POWER “ON”. THE HIGH
VOLTAGE SECTION OF THE POWER SUPPLY
INCLUDING FILAMENT LEADS IS 4000 VOLTS
POTENTIAL WITH RESPECT TO GROUND.
6-1
SERVICE INFORMATION
PRECAUTIONS AND REPAIR SERVICE TIPS
PRELIMINARY
A. SINCE NEARLY 2,100 VOLTS EXISTS IN SOME
CIRCUITS OF THIS UNIT REPAIRS SHOULD BE
CARRIED OUT WITH GREAT CARE.
The filament leads of magnetron carry High
Voltage with respect to ground. Extreme caution
must be exercised. Never plug the unit into a
power source to determine which component is
defective in high voltage section.
B. TO AVOID POSSIBLE EXPOSURE TO
MICROWAVE ENERGY LEAKAGE, THE
FOLLOWING PRECAUTIONS MUST BE TAKEN
BEFORE SERVICING.
(1) Before the power is applied:
(a) Make sure the primary interlock switch, the
secondary interlock switch and the interlock
monitor switch operate properly by opening
and closing the door several by opening and
closing the door several times.
(b) Make sure the perforated screen and the
dielectric choke of the door are correctly and
firmly mounted.
(2) After power is applied:
(a) Make sure the interlock switch mechanism
is operating properly by opening and closing
the door.
(b) Check microwave energy leakage must
be below
the limit of 5 mW/cm2.
(All service adjustments should be made for
minimum microwave energy leakage
readings).
(3) Do not operate the unit until it is completely
repaired, if any of the following conditions exist.
The unit must not be operated.
(a) The door does not close firmly.
(b) The hinge is broken.
(c) The door seal is damaged.
(d) The door is bent or warped, or there is any
other visible damage on the unit that may
cause microwave energy leakage.
NOTE: Always keep the seal clean.
(e) Make sure that there are no defective parts
in the interlock mechanism.
(f) Make sure that there are no detective parts
in the microwave generating and transmission
assembly (especially waveguide).
(4) The following items should be checked after the
unit is repaired:
(a) The interlock monitor switch is connected
correctly and firmly.
(b) The magnetron gasket is properly positioned
and mounted.
(c) The waveguide and the oven cavity are intact.
(no microwave energy leakage)
(d) The door can be properly closed and the
safety switches work properly.
(e) The unit must stop when the door is opened or
the time is up.
The unit must not be operated with any of the above
components removed or by-passed.
7-1
MICROWAVE LEAKAGE TEST
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
manufacture 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.
• 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. ( 1 in/sec)
EQUIPMENT
•
TESTER (VOLTS-DC, AC, Ohmmeter)
• Microwave survey meter
- Holaday HI-1500
HI-1501
- Narda 8100
8200
• 600 cc non conductive material beaker (glass or
plastic), inside diameter: approx. 8.5 cm (31/2in.)
• Glass thermometer: 100°C or 212°F (1 deg scale)
• It should not exceed 4 mW/cm2.
7-2
MEASUREMENT WITH THE OUTER CASE
REMOVED
(1) 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. Special care should be
taken in measuring the following parts.
- Around the magnetron
- The waveguide
WARNING: AVOID CONTACTING ANY HIGH
VOLTAGE PARTS.
MEASUREMENT WITH A FULLY
ASSEMBLED OVEN
(1) After all components, including the outer
panels, are fully assembled, measure for
microwave energy leakage around the door
viewing window, the exhaust opening and air
inlet openings.
(2) Microwave energy leakage must not exceed the
values prescribed below.
NOTES:
Leakage with the outer panels removed - less
than 5 mW/cm2.
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/cm2.
NOTE WHEN MEASURING
(1) Do not exceed meter full scale deflection.
(2) The test probe must be removed no faster than
1 inch/sec (2.5cm/sec) along the shaded area,
otherwise a false reading may result.
(3) 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.
(4) 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.
RECORD KEEPING AND NOTIFICATION
AFTER MEASUREMENT
(1) 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.
(2) Should the microwave energy leakage not be
more than 2 mW/cm2after determining that all
parts are in good condition, functioning properly
and genuine replacement parts which are listed in
this manual have been used.
(3) At least once a year, have the electromagnetic
energy leakage monitor checked for calibration
by its manufacturer.
7-3
DISASSEMBLY INSTRUCTIONS
Figure 1
Control Panel
Screw
Power
Transformer
(CN2)
(CN1)
(Relay 2)
(CN6)
(Relay 11)
(CN5)
(CN3)
(CN8)
Circuit Board
Figure 2
FPC Connector(S1)
Control Bracket
Circuit Board
Figure 3
IMPORTANT NOTES:
UNIT MUST BE DISCONNECTED FROM ELECTRICAL OUTLET WHEN MAKING REPAIRS, REPLACEMENTS, ADJUSTMENTS AND CONTINUITY CHECKS. WAIT AT LEAST ONE MINUTE,
UNTIL THE HIGH VOLTAGE CAPACITOR IN THE
HIGH VOLTAGE POWER SUPPLY HAS FULLY
DISCHARGED.
THE CAPACITOR SHOULD BE DISCHARGED BY
USING INSULATED WIRE - I.E. TEST PROBE
CONNECTED TO 10K-OHM RESISTOR IN SERIES
TO GROUND.
WHEN RECONNECTING THE WIRE LEADS TO
ANY PART, MAKE SURE THE WIRING CONNECTIONS AND LEAD COLORS ARE CORRECTLY
MATCHED ACCORDING TO THE OVERALL CIRCUIT DIAGRAM. (ESPECIALLY SWITCHES AND
HIGH VOLTAGE CIRCUIT.)
A. REMOVING POWER AND CONTROL
CIRCUIT BOARD (Figures 1, 2 and 3)
(1) Disconnect power at the main fuse or circuit
breaken, or pull the plug. Remove the top grille by
removing the two screws that hold it in place.
(2) Remove a screw securing the control panel
assembly to the oven cavity.
(3) Remove the control panel with pushing it upward.
(4) Remove the six connectors (CN1, CN2, CN3, CN5,
CN6, CN8) and wire leads (Relay2, Relay11) from
the circuit board.
(5) Remove 7 screws securing the circuit board.
(6) Remove the FPC connector from the terminal
socket following “HOW TO REMOVE THE FPC
CONNECTOR” on the next page.
(7) Remove the knob.
(8) Remove the circuit board from the control bracket
carefully.
7-4
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