Lg Lmvm1945sb, Lmvm1945sbq, Lmvm1945t, Lmvm1945sw Service Manual

MICROWAVE OVEN

SERVICE MANUAL

MODEL: LMVM1945SW

BEFORE SERVICING THE UNIT, READ THE

SAFETY PRECAUTIONS IN THIS MANUAL.

LMVM1945SB LMVM1945SBQ LMVM1945T

CAUTION

Website: http://us.lgservice.com

CAUTION

SAFETY PRECAUTIONS

PRECAUTIONS TO BE OBSER VED 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 ......................................................................................................... Inside front page

SPECIFICATIONS.......................................................................................................................................... 1-1

CAUTIONS..................................................................................................................................................... 2-1

INSTALLATION.............................................................................................................................................. 3-1

OPERATING INSTRUCTIONS....................................................................................................................... 4-1

CONTROL PANEL ................................................................................................................................. 4-1

CONTROL PANEL INSTRUCTIONS ..................................................................................................... 4-2

OVERALL CIRCUIT DIAGRAM...................................................................................................................... 5-1

SCHEMATIC DIAGRAM......................................................................................................................... 5-1

MATRIX CIRCUIT FOR TOUCH KEY BOARD...................................................................................... 5-2

GENERAL INFORMATION FOR SERVICE................................................................................................... 6-1

GENERAL PRECAUTIONS IN USE ...................................................................................................... 6-1

TRIAL OPERATION ............................................................................................................................... 6-1

FEATURES AND SPECIFICATIONS FEATURES................................................................................. 6-1

SERVICE INFORMATION ............................................................................................................................. 7-1

PRECAUTIONS AND REPAIR SERVICE TIPS..................................................................................... 7-1

MICROWAVE LEAKAGE TEST............................................................................................................. 7-2

POWER OUTPUT MEASUREMENT ..................................................................................................... 7-3

DISASSEMBLY INSTRUCTIONS .......................................................................................................... 7-4

INTERLOCK SYSTEM .......................................................................................................................... 7-11

INTERLOCK CONTINUITY TEST.......................................................................................................... 7-13

TEST AND CHECKOUT PROCEDURES AND TROUBLESHOOTING................................................. 7-14

A. TEST PROCEDURES................................................................................................................ 7-14

B. CHECKOUT PROCEDURES..................................................................................................... 7-16

C. TROUBLESHOOTING............................................................................................................... 7-20

EXPLODED VIEW.......................................................................................................................................... 8-1

REPLACEMENT PARTS LIST............................................................................................................... 8-9

SCHEMATIC DIAGRAM OF P.C.B.

.......................................................................................................... 8-17

PRINTED CIRCUIT BOARD

..................................................................................................................... 8-18

P.C.B. PARTS LIST

................................................................................................................................. 8-19

1-1

Rated Power Consumption..................................................1,400W maximum (Microwave oven+Cook top lamps+Ventilation fan)

Microwave Output.................................................................1170W (IEC 60705)

Adjustable 117W through 1170W, 10 steps

Frequency.............................................................................2,450 MHz 50 MHz

Power Supply........................................................................120 VAC, 60 Hz

Rated Current.......................................................................12 Amp. (Microwave oven+Cook top lamps+Ventilation fan)

Magnetron Cooling...............................................................Forced Air Cooling

Rectification...........................................................................Rectification Voltage Double Half-Wave

Door Sealing.........................................................................Choke System

Safety Devices......................................................................Thermostat:

Open at 110°C 5°C Close at 0°C 5°C

Fuse(20A)

Primary Interlock Switch

Secondary Interlock Switch

Interlock Monitor Switch

Inverter .................................................................................120 V

Magnetron.............................................................................2M261

Cook top Lamp.....................................................................125 V, 20 W 2EA(Halogen)

Cavity Lamp..........................................................................125 V, 20 W (Halogen)

Timer.....................................................................................Digital, up to 99 mim. 99 sec. (in each cooking stage)

Tray .......................................................................................Tempered Safety Glass

Overall Dimensions..............................................................29

/16”(W)x167/16”(H)x155/8”(D)

Oven Cavity Size .................................................................23

/2”(W)x103/16”(H)x141/2”(D)

Effective Capacity of Oven Cavity.......................................1.9 Cu.ft.

Accessories...........................................................................Owner’s Manual & Cooking Guide, Installation Manual,

Exhaust Adapter, Exhaust Damper, Mounting Kit and Two Filters, Rotating Ring Assembly, Metal Rack, Glass Tray, Defrosting Net.

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

3-1

INSTALLATION

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.

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.

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

CONTROL PANEL

4-1

OPERATING INSTRUCTIONS

17 19 21 25 26

18 20 22

23 24

2 3 4 8 10 11 13

6 9 12 14 16

15 1

CONTROL PANEL INSTRUCTIONS

4-2

1. DISPLAY: The Display includes a clock and

indicators to tell you time of day, cooking time settings and cooking functions selected.

2. POPCORN: Touch this pad when popping popcorn

in your microwave oven.

3. POTATO: Touch this pad to cook potatoes.

4. RICE: Touch this pad to cook rice.

5. VEGETABLE: Touch this pad to cook vegetables.

6. FROZEN ENTREE: Touch this pad to cook frozen

entree.

7. REHEAT: Touch this pad to reheat casserole,

dinner plate soup/sauce and pizza.

8. CHICKEN CHOICES: Touch this pad to cook

chicken wings, chicken nuggets, spicy chicken and mexican chicken.

9. HOMEMADE BAKERY: Touch this pad to cook

roll/muffin, pancake, and french toast.

10. LARGE DISH MENUS: Touch this pad to cook

lasagna, whole chicken, and casserole.

11. SOFTEN: Touch this pad to soften ice cream,

cream cheese, butter, or frozen juice.

12. MELT: Touch this pad to melt chocolate, cheese,

butter, or marshmallows.

13. AUTO DEFROST: Touch this pad to select food

type and defrost food by weight.

14. Q DEFROST: This pad provides you with the

RAPID defrosting method for 1.0 pound ground beef.

15. HOLD WARM: Touch this pad to keep hot, cooked

foods warm in your microwave oven for up to 99 minutes 99 seconds.

16. CUSTOM SET: Touch this pad to change the

oven’s default settings for clock set, sound, display speed and defrost weight.

17. TIMER: Touch this pad to set the kitchen timer.

18. LIGHT TIMER: Touch this pad to set the light

timer.

19. COOK TIME: Touch this pad followed by Number pads to set a cooking time.

20. POWER LEVEL: Touch this pad to select a cooking power level.

21. MORE: Touch this pad to add ten seconds of cooking time each time you press it.

22. LESS: Touch this pad to subtract ten seconds of cooking time each time you press it.

23. NUMBER: Touch number pads to enter cooking time, power level, quantities, or weights.

24. Ez-ON: Touch this pad to set and start quickly at 100% power level.

25. STOP/CLEAR: Touch this pad to stop the oven or to clear all entries.

26. START: Touch this pad to start a function. If you open the door after oven begins to cook, START again.

27. LIGHT HI-LOW-OFF: Touch this button to turn on the cooktop/countertop light.

28. VENT 5 LEVELS: Touch this button to turn the fan on or off.

5-1

SCHEMATIC DIAGRAM

OVERALL CIRCUIT DIAGRAM

5-2

MATRIX CIRCUIT FOR TOUCH KEY BOARD

6-1

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. Two short and a 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) 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 0W to

1170W can be selected by the touch control and electronic computer system.

C. Cooking time can be displayed on the digital

readout.

D. Three different cooking stages (Include Defrost)

can be changes from one cooking stage to another. This is made possible with the memory function of the microprocessor.

GENERAL INFORMATION FOR SERVICE

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 bebelow

the limit of 5 mW/cm

(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

PRECAUTIONS AND REPAIR SERVICE TIPS

SERVICE INFORMATION

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

- 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 Health 1390 Piccard Drive Rockville, Maryland 20850

•

The service personnel should check all surface and

vent openings for microwave emission testing.

•

Check for microwave energy leakage after every

servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 1mW/cm.sq. And always start measuring of an unknown field to assure safety for operating personnel from radiation leakage. NOTE: The standard is 5mW/cm.sq. while in the customer’s home. 1mW/cm.sq. stated here is manufacturer’s own voluntary standard for units in customer’s home.

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 (3

/2 in.)

• Glass thermometer: 100°C or 212°F (1 deg scale)

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 oven.

• 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)

7-2

MICROWAVE LEAKAGE TEST

7-3

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/cm

Leakage for a fully assembled oven (“Before the latch switch (primary) is interrupted”) with the door in a slightly opened position - less than 1 mW/cm

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 1 mW/cm

after 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.

(1) Microwave power output measurement is made

with the microwave oven supplied at its rated voltage and operated at its maximum microwave power setting with a load of (1000±5) g of potable water.

(2) The water is contained in a cylindrical borosilicate

glass vessel having a maximum material thickness of 1/8” (3 mm) and an outside diameter of approximately

7.6” (190mm).

(3) The oven and the empty vessel are at ambient

Temperature(T0) prior to the start of the test.

(4) The initial temperature (T1) of the water is

(10±1)°C (50°F) It is measured immediately before the water is added to the vessel. After addition of the water to the vessel, the load is immediately placed on the center of the turntable which is in the lowest position and the microwave power switched on.

(5) The time t for the temperature of the water to rise

by a value T of (10±1)°K is measured, where t is the time in seconds and T is the temperature rise. The initial and final water temperatures are selected so that the maximum difference between the final water temperature and the ambient temperature is 5°K.

(6) The microwave power output P in watts is calculated

from the following formula :

4,187 Mw(T2 –T1)+0.55Mc(T2 –T0)

is measured while the microwave generator is operating at full power. Magnetron filament heat-up time is not included. (about 5 sec)

(7) The water is stirred to equalize temperature

throughout the vessel, prior to measuring the final water temperature.

(8) Stirring devices and measuring instruments are

selected in order to minimize addition or removal of heat.

WATER LOAD

GLASS TRAY

P =

POWER OUTPUT MEASUREMENT

Where

P is the microwave power output, in watts: Mw is the mass of the water, in grams: Mc is the mass of the container, in grams: T0 is the ambient temperature, in °C: T1 is the initial temperature of the water, in °C: T2 is the final temperature of the water, in °C: t

is the heating time in seconds, excluding the magnetron filament heat- up time.

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