GE MV1526B User Manual

MICROWAVE OVEN

SERVICE MANUAL

MODEL: MV1526W

CAUTION

BEFORE SERVICING THE UNIT, READ THE

SAFETY PRECAUTIONS IN THIS MANUAL.

MV1526B

website http://www.lgservice.com
e-mail http://www.lgeservice.com/techsup.html

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 CSA 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 .......................................................................................................................... 7-12

INTERLOCK CONTINUITY TEST.......................................................................................................... 7-14

TEST AND CHECKOUT PROCEDURES AND TROUBLE SHOOTING................................................ 7-15

A. TEST PROCEDURES................................................................................................................ 7-15

B. CHECKOUT PROCEDURES..................................................................................................... 7-18

C. TROUBLE SHOOTING.............................................................................................................. 7-21

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

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

SCHEMATIC DIAGRAM OF PCB .......................................................................................................... 8-12

PRINTED CIRCUIT BOARD .................................................................................................................. 8-13

PCB PARTS LIST................................................................................................................................... 8-14

1-1

Rated Power Consumption..................................................1,500W maximum (Microwave oven+Cook top lamps+Ventilation fan)

Microwave Output.................................................................1,000W (IEC 60705)

Adjustable 100W through 1000W, 10 steps

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

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

Rated Current.......................................................................13 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......................................................................Oven Cavity Thermostat:

Open at 90°C ± 5°C

Fuse(20A)

Primary Interlock Switch

Secondary Interlock Switch

Interlock Monitor

Magnetron.............................................................................2M214-39F

High Voltage Capacitor........................................................Capacitor: 1.0µF, 2.1 KV AC

High Voltage Diode...............................................................Diode; 350mA, 9.0 KV

Cook top Lamp.....................................................................125 V, 30 W

Cavity Lamp..........................................................................125 V, 30 W

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

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

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

15

/16”(W)x167/16”(D)x153/8”(H)

Oven Cavity Size .................................................................19

7

/8”(W)x143/16”(D)x815/16”(H)

Effective Capacity of Oven Cavity.......................................1.5 Cu.ft.

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

Exhaust Adapter, Exhaust Damper, Mounting Kit and Two Filters,
Rotating Ring Assembly.

SPECIFICATIONS

2-1

CAUTIONS

• 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 watch 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.

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

1

2

4

7

10

13

16

21

18

3

6

5

8

12

14

17

19

15

20

9

11

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 from 1 to 4.

4. BEVERAGE: Touch this pad to reheat one cup or two

cups a beverage.

5. PIZZA: Touch this pad to reheat 1 to 3 slices.

6. TIME DEFROST: Touch this pad to defrost most other

frozen foods.

7. FROZEN ENTREE: Touch this pad to cook frozen entrees

by choosing a preset weight.

8. AUTO COOK: Touch this pad to cook vegetables, rice, or

casseroles.

9. AUTO REHEAT: Touch this pad to reheat dinner plate,

soup/sauce, casserole, roll/muffin.

10. AUTO DEFROST: Meat, poultry, fish. Touch on pad to

select food type and defrost food by weight.

11. NUMBER: Touch number pads to enter cooking time,

power level, quantities or weights.

12. TIME COOK: Touch this pad to set a cooking time.

13. POWER LEVEL: Touch this pad to select a cooking

power level.

14. CUSTOM SET: Touch this pad to change the oven’s
default settings for sound, clock, display speed, defrost
weight, and demo mode operations.

15. KITCHEN TIMER: Touch this pad to set the kitchen
timer.

16. CLOCK: Touch this pad to enter the time of day.

17. FAN HI/LO/OFF: Touch this pad to turn the fan on or off.

18. LIGHT HI/LO/OFF: Touch this pad to turn on the

cooktop/countertop light.

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

20. EZ ON: Touch this pad to set and start quickly at 100%
power level.

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

5-1

SCHEMATIC DIAGRAM

OVERALL CIRCUIT DIAGRAM

MATRIX CIRCUIT FOR TOUCH KEY BOARD

CUSTOM

SET

AUTO

COOK

TIME

COOK

KITCHEN

TIMER

POWER

LEVEL

N.C

N.C

Ez OnCLOCK

STOP/

CLEAR

TIME

DEFROST

AUTO

DEFROST

AUTO

REHEAT

5-2

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. 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 thermal fuse
(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.

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

2

.

(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

7-2

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.

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

1

/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 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 an
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)

MICROWAVE LEAKAGE TEST

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

2

.

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/cm

2

.

NOTE WHEN MEASURING

(1) Do not exceed meter full scale deflection.
(2) The test probe must be moved 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 by 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 being
tested. (Hold vertically when testing the top and
bottom, and horizontally along the side.)

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.

(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 prior to the start of the test.

(4)

The initial temperature (T1) of the water is (10±2)°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±2)°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 :

4187 x (∆T)

T

is measured while the microwave generator is
operating at full power. Magnetron filament heat-up
time is not included. (about 3 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.

7-3

WATER LOAD

TURNTABLE

P =

POWER OUTPUT MEASUREMENT

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) Remove a screw securing the control panel

assembly to the oven cavity.
(2) Remove the control panel with pushing it upward.
(3) Remove the connector (CN1) and wire leads

(Relay6) from the circuit board.

(4) Remove 3 screws securing the circuit board.

(5) Remove the FPC connector from the terminal

socket following “HOW TO REMOVE THE FPC
CONNECTOR” on the next page.

(6) Remove the circuit board from the control bracket

carefully.

7-4

Circuit Board

Figure 2

Figure 3

Control Bracket

FPC Connector(S1)

Circuit Board

DISASSEMBLY INSTRUCTIONS

Figure 1

Screw

Control Panel

(Relay 7)

Relay 7

Power Transformer

(CN1)

7-5

HOW TO REMOVE THE F.P.C. CONNECTOR

Follow the steps below as illustrated in Figures 4
and 5 to remove the F.P.C. connector.

(1) Hold the edges of the plastic fastener with

thumb and forefinger.
(Figure 4)

(2) Lift up the lever of the plastic fastener from

the terminal socket by lightly pressing the
lever end with forefinger.
(Figure 5)

(3) Remove the F.P.C. connector from the

terminal socket.

HOW TO INSERT THE F.P.C. CONNECTOR

Follow the steps below as illustrated in Figures 6
and 7 to insert the F.P.C. connector.
(1) Insert the F.P.C. connector into the terminal

socket securely with the fingers.

(2) Hold the plastic fastener with thumb and

forefinger of the other hand, and push it
slowly into the terminal socket. (Figure 6)
NOTE: When reconnecting the F.P.C

connector make sure that the holes
on the F.P.C. connector are properly
engaged with the hooks on the plastic
fastener

(3) Lock the level of the plastic fastener into the

hook of the terminal socket securely by
releasing the fingers.
(Figure 7)

Figure 4

Figure 7

Figure 6

Figure 5

Plastic fastener

Plastic fastener

Hook

F.P.C.
Connector

Plastic fastener

Holes

Terminal
socket

F.P.C.
Connector

Hook

Terminal
socket

Holes

F.P.C.
Connector

Terminal
socket

Plastic
fastener

F.P.C.
Connector

Terminal
socket

B. REMOVING THE OUT CASE(Figure 8)

(1) Remove the vent grille by removing two screws

securing it to the out case.
(2) Remove two screws securing it to the front bracket.
(3) Remove two screws securing it to the air duct.
(4) Remove the mounting plate by turning the two

screws securing it to the out case.
(5) Remove the base plate by removing six screws

securing it to the out case. Remove the Mount, All

from the out case by removing two screws securing

it to the out case and one screw securing it to the

ventilation motor ASS'Y and cavity.

(6) Remove the power cord cover from outcase by

removing a screw.

(7) Remove the power cord to the inner of the out c

ase with turning power cord and remove the out
case with pushing it back.

Vent Grille

Controller

Mounting
Plate

Door

Out Case

Mount, All

Figure 8

Power code

7-6

Latch Board

WH

(from H.V.Transformer)
WH(from Monitor S/W)
WH

(

from Oven Thermostat

)

WH(from Cooktop lamp

Secondary Interlock Switch

Monitor Interlock Switch

Primary Interlock Switch

GN(from P.C.B)

YL(from P.C.B)

WH

(from Secondary switch)

RD

(from Ry 7)

Figure 9

Latch Board

Secondary
Interlock Switch

Interlock
Monitor Switch

Primary
Interlock Switch

Figure 10

WIRE COLOR

SYMBOL COLOR

WH
BK
BR
RD
BL
PK
GY

N.P.

WHITE
BLACK
BROWN
RED
BLUE
PINK
GREY

GN

GREEN
Not Provided

7-7

C REMOVING THE DOOR INTERLOCK

SWITCHES (Figures 9,10)

(1) Disconnect the wire leads from the interlock

switches.
(2) Remove two screws securing the Latch Board.
(3) Make necessary replacements and check

microwave energy leakage according to

“ADJUSTMENT PROCEDURE” on page 7-12.

Figure 13

Figure 11

Figure 12

vertgrille

mount all

outcase

Magnetron

D. REMOVING MAGNETRON

(Figures 11 Through 13)

(1) Remove vertgrille.
(2) Remove mount all.
(3) Remove outcase.
(4) Discinnect the wireleads.
(5) Remove the 3 screws and Magnetron very

carefully.

NOTES:

• When removing the magnetron, make sure that its
dome does not hit any adjacent parts, or it may be
damaged.

• When replacing the magnetron, be sure to install the
magnetron gasket in the correct position and be sure
that the gasket is in good condition.

• After replacing the magnetron, check for microwave
energy leakage with a survey meter Check
microwave energy leakage must be below the limit of
5 mW/cm

2

. (All service adjustments should be made

for minimum microwave energy leakage readings.)

7-8

E. REMOVING DOOR (Figure 14)

(1) Remove the vent grille by two screws securing it to

the outcase loosening.

(2) Lift up and draw the door.

NOTES:

• After replacing the door, be sure to check that the
primary interlock switch, the secondary interlock
switch and the interlock monitor switch is in good
operating normally.

• After replacing the door, check for microwave energy
leakage with a survey meter. Microwave energy
leakage must be below the limit of 5mW/cm

2

. (With a

275 ml water load)

F. DISASSEMBLING DOOR (Figure 15)

(1) Remove the dielectric choke by using knife

blade or small screw driver, etc.

(2) Remove two screws securing it to the door handle.

CAUTION: Be careful not to damage door seal

plate with the screwdriver.

7-9

Door Screen

Figure 15

Figure 14

G. ASSEMBLING DOOR

(1) When mounting the door assembly to the oven

assembly, be sure to adjust the door assembly
parallel to the chassis. Also adjust so the door has no
play between the inner door surface and oven frame
assembly. If the door assembly is not mounted
properly, microwaves may leak from the clearance
between the door and the oven.

H. REMOVING THE VENTILATION FAN

ASS’Y

(1) Remove the mounting plate by removing two

screws securing it to the back plate.
(See Figure 16)

(2) Remove the two screws securing the MOUNT, ALL

and one screw securing the ventilation fan ASS'Y.
(See Figure 17)

(3) Carefully pull the ventilation motor ASS'Y out of the

microwave oven. (See Figure18)

7-10

MOUNT , ALL

Figure 16

Figure 17

Figure 18

Space

I. REMOVING THE TURNTABLE MOTOR

(1) Remove the turntable.
(2) Remove the turntable shaft VERY CAREFULLY

with a slotted screwdriver. (Figure 19)

(3) Remove the base plate by removing 6 screws

securing it to the oven cavity. (Figure 20)

(4) Disconnect the leadwire from the turntable motor

terminals.

(5) Remove the 2 screws securing the turntable motor

to the oven cavity ASS'Y. (Figure 21)

NOTES:

• Remove the leadwire from the turntable motor VERY
CAREFULLY.

• Be sure to grasp the connector not the wires when
removing.

Wire Leads

Turntable Motor

Figure 21

Figure 19

Figure 20

7-11

7-12

ADJUSTMENT PROCEDURES

To avoid possible exposure to microwave energy
leakage, adjust the door latches and interlock
switches, using the following procedure.

The Interlock Monitor and Primary Interlock Switch act
as the final safety switch protecting the user from
microwave energy. The terminals between “COM” and
“NC” of the Interlock Monitor must close when the door
is opened. After adjusting the Interlock Monitor Switch,
make sure that it is correctly connected.
Mounting of the primary/monitor/secondary switches to
the latch board.

CHECK THE DOOR LATCH AND SWITCH
CLOSING.

NOTE:

The outer cover of the microwave oven is
removed.

(1) Set the microwave oven on its side so that you can

see the latch board and the switches, as shown in
Figure 22.

(2) Close the door tightly and check gaps A and B to

be sure they are no more than 1/64” (0.5 mm).
See Figure 23 for close-up view of gaps A and B
(door latches). If all gaps are less than 1/64”
(0.5 mm), adjustment of the latch board may not
be necessary. Go to Steps 5 and 6 to check the
sequence of the switches.

NOTE:

To correct sequence of the Primary Interlock
Switch, Secondary Interlock Switch and the
Interlock Monitor Switch is very important.

If any gap is larger than 1/64” (0.5 mm), you will
need to adjust the latch board”. Go to step 3
and follow all steps in order.

ADJUST THE LATCH AND SWITCH CLOSING

(3) Loosen the two screws holding the plastic latch

board as shown.

(4) With the oven door closed tightly, move the latch

board upward toward the top of the oven and/or
away from the door latch until the gaps are less
than 1/64” (0.5 mm).
Hold the latch board tightly in this position until you
check the sequence of the switches in steps 5
and 6.

LATCH

LATCH BOARD

0-1/64"

0-1/64"

Latch Board

Secondary
Interlock Switch

Interlock
Monitor Switch

Primary
Interlock Switch

Figure 22

Figure 23

INTERLOCK SYSTEM

INTERLOCK MECHANISM

The door lock mechanism is a device which has been specially designed to eliminate completely microwave
activity when the door is opened during cooking and thus to prevent the danger resulting from the microwave
leakage.

7-13

TEST THE LATCH AND SWITCH SEQUENCE

(5) Open the oven door slowly. Watch the door latch,

the Secondary Switch. Release Rod and Lever
on the switches to make sure they are zero to the
body of the switches in the following sequence:

- Primary Interlock Switch

- Secondary Interlock Switch

- Interlock Monitor Switch
Adjust the latch board until the switches operate in

this sequence. See Steps 3 and 4.

(6) Close the oven door slowly and be sure it is tightly

closed. Watch the three switches to make sure
they are zero to the body of the switches in the
following sequence:

- Interlock Monitor Switch

- Primary Interlock Switch

- Secondary Interlock Switch
NOTE: The Interlock Monitor Switch is an added

safety check on the Primary and
Secondary Interlock Switches. If the
Primary and Secondary Interlock Switches
allow the oven to operate with the door
open, the Monitor Switch will blow the
fuse.

(7) When you achieve the proper sequence of

switches in Steps 5 and 6, tighten the latch board
screws at that point.

TEST THE MICROWAVE ENERGY LEAKAGE

Make sure the microwave energy leakage is below the
limit of 1mW/cm2 (with a 275 ml water load) and
5mW/cm2 (with a 275 ml water load without the
cabinet) when measured with a survey meter.

7-14

A. PRIMARY INTERLOCK SWITCH TEST

When the door is opened slowly, an audible click
should be heard at the same time or successively
at intervals and the latches should activate the
switches with an audible click.
If the latches do not activate the switches when the
door is closed, the switches should be adjusted in
accordance with the adjustment procedure.
Disconnect the wire lead from the primary switch.
Connect the ohmmeter leads to the common
(COM) and normally open (NO) terminal of the
switch. The meter should indicate an open circuit
in the door open condition.
When the door is closed, the meter should indicate
a closed circuit.
When the primary switch operation is abnormal,
make the necessary adjustment or replace the
switch with the same type of switch.

B. SECONDARY INTERLOCK SWITCH TEST

Disconnect the wire lead from the secondary
switch.
Connect the ohmmeter leads to the common
(COM) and normally open (NO) terminals of the
switch. The meter should indicate an open circuit
in the door open condition. When the door is
closed, the meter should indicate a closed circuit.
When the secondary switch operation is abnormal,
make the necessary adjustment or replace the
switch only with the same type of switch.

C. MONITOR SWITCH TEST

Disconnect the wire lead from the monitor switch.
Connect the ohmmeter leads to the common
(COM) and normally closed (NC) terminals of the
switch. The meter should indicate a closed circuit
in the door open condition. When the door is
closed, the meter should indicate an open circuit.
When the monitor switch operation is abnormal,
replace with the same type of switch.

NOTE: After repairing the door or the interlock
system, it is necessary to do this continuity
test before operating the oven.

WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION

EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS.

TYPE NO. SZM-V16-FA-63 OR VP-533A-OF OR V-5230Q FOR PRIMARY SWITCH
TYPE NO. SZM-V16-FA-62 OR VP-532A-OF OR V-5220Q FOR MONITOR SWITCH
TYPE NO. SZM-V16-FA-63 OR VP-533A-OF OR V-5230Q FOR SECONDARY SWITCH

COMPONENTS TEST PROCEDURE RESULTS

SWITCHES Check for continuity of the Door Door
(Wire leads removed) switch with an Ohm-meter open closed

Primary
Switch

Monitor
Switch

Secondary
Switch

NOTE : After checking for the continuity of switches, make sure that they are

connected correctly.

INTERLOCK CONTINUITY TEST

COM

NO

NC

COM

COM

NO

7-15

- CAUTIONS -

- DISCONNECT THE POWER SUPPLY CORD

FROM THE WALL OUTLET WHENEVER
REMOVINGING THE CABINET FROM THE UNIT.
PROCEED WITH THE TESTS ONLY AFTER
DISCHARGING THE HIGH VOLTAGE CAPACITOR
AND REMOVING THE WIRE LEADS FROM THE
PRIMARY WINDING OF THE HIGH VOLTAGE
TRANSFORMER. (SEE FIGURE 24)

- ALL OPERATIONAL CHECKS WITH MICROWAVE

ENERGY MUST BE DONE WITH A LOAD (1 LITER
OF WATER IN CONTAINER) IN THE OVEN.

A. TEST PROCEDURES

COMPONENTS TEST PROCEDURES RESULTS

MAGNETRON

(Wire leads are

removed)

HIGH-VOLTAGE

TRANSFORMER

(Wire leads are

removed)

1) Measure the resistance: Across the
filament terminals of the magnetron
with an ohm-meter on Rx1 scale.

2) Measure the resistance: Between
each filament terminal of the
magnetron and the chassis ground
with an ohm-mater on high test scale.

1) Measure the resistance:

With an ohm-meter on Rx1 scale.
a. Primary winding;
b. Filament winding;
c. Secondary winding;

2) Measure the resistance:

With an ohm-meter on highest scale.
a. Primary winding to ground;
b. Filament winding to ground;

Normal reading:

Less than 1 ohm.

Normal reading:

Infinite ohms.

NOTE: Replace the magnetron, if the
magnetron checks and all of the
high voltage component tests are
good, but the unit still does not heat
a load.

Normal readings:

Approx. 0.3 to 0.5 ohm.
Less than 0.1 ohm.
Approx. 65 to 120 ohms.

Normal readings:

Infinite ohms.
Infinite ohms.

NOTE: A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS

SERVICED FOR ANY REASON.

Primary
Winding

Secondary
Winding

Filament
Winding

Figure 24

TEST AND CHECKOUT PROCEDURES, AND TROUBLE SHOOTING

7-16

COMPONENTS TEST PROCEDURES RESULTS

HIGH-VOLTAGE

CAPACITOR

HIGH-VOLTAGE

DIODE

Measure the resistance:
(1) Terminal to terminal

Ohm­meter

Figure 25-a

(2) Terminal to case

Ohm­meter

Figure 25-b

Measure the continuity:
(1) Forward

Ohm­meter

Figure 26-a

(1) Reverse

Ohm­meter

Figure 26-b

Normal reading:

Momentarily indicates several ohms,
and then gradually returns to infinite
ohms.

Abnormal reading:

Indicates continuity or infinite ohms
from the beginning.

Normal readings:

Infinite.

Abnormal reading:

Indicates continuity.

Normal readings:

continuity.

Abnormal reading:

Infinite.

Normal readings:

Infinite.

Abnormal reading:

continuity.

Measure the resistance between terminal
pins of connector KEY CONNECTOR.

NOTE:

When reconnecting the FPC connector,
make sure that the holes on the FPC
connector are properly engaged with hooks
on the plastic fastener.

MATRIX CIRCUIT FOR

TOUCH KEY BOARD

CONNECTOR(KEY CON)

(For detail matrix circuit of each model,

refer to page 5-2.)

7-17

COMPONENTS TEST PROCEDURES RESULTS

TOUCH KEY

BOARD

Resistance

value

When When not
touched touched

Less than More than
400 ohms 1 mega ohm

1
2
3
4
5
6
7
8
9
10
11
12
13

FPC CONNECTOR

Top

Figure 28

Figure 27

CUSTOM

SET

N.C

STOP/

CLEAR

AUTO
COOK

AUTO

REHEAT

Ez OnCLOCK

TIME

DEFROST

TIME

COOK

AUTO

DEFROST

KITCHEN

TIMER

POWER

LEVEL

N.C

7-18

COMPONENTS TEST PROCEDURES RESULTS

RELAY2

Check for continuity of relay 2 with an
ohm-meter.
(Remove wire leads from relay 2 and
operate the unit.)

NOTES:

• A MICROWAVE ENERGY TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR
ANY REASON.

• MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION.

• WHEN REMOVING THE WIRE LEADS FROM THE PARTS, BE SURE TO GRASP THE CONNECTOR, NOT

THE WIRES.

B. CHECKOUT PROCEDURES

(1) CHECKOUT PROCEDURES FOR FUSE BLOWING

CAUTION: REPLACE BLOWN FUSE WITH 20 AMPERE FUSE.

Fuse blows immediately after
the door is closed.

Fuse blows immediately after
the door is opened.

Fuse blows when the door is closed and START
key is touched.

Improper operation of the primary interlock, secondary
interlock switches and/or the interlock monitor switch.

Malfunction of the high voltage transformer; the high
voltage capacitor including the diode, the magnetron,
the blower motor or the circuit board.

PROBLEMS CAUSES

POWER

LEVEL

1
2
3
4
5
6
7
8
9

10

4 sec
6 sec

8 sec
10 sec
12 sec
14 sec
16 sec
18 sec
20 sec
22 sec

18 sec
16 sec
14 sec
12 sec
10 sec

8 sec
6 sec
4 sec
2 sec

0

NOTES:

• If the fuse is blown by an improper switch operation, replace the all Interlock switches, PCB Ass’y and the fuse at
the same time. After replacing the the all Interlock switches, PCB Ass’y,Fuse with new ones, make sure that they
are correctly connected.

• Check for microwave energy leakage according to INTERLOCK ADJUSTMENT PROCEDURES on page 7-12
when the primary interlock, secondary interlock switches and/or the interlock monitor switches are adjusted or
replaced.

Relay 2

Figure 29

CAUTION : The relay connector
2(White) and 5(Red) must be correctly
connected Relay 6.
These two connectors are not Inter­changeable.

7-19

(2) CHECKOUT PROCEDURES FOR RELAY.

- PROBLEM (A) -

T.T. motor and oven lamp turn on without touching

START key when the door is closed.

Remove the mate connector of I/O
CON from the circuit board.
Does the unit still operate?

GOOD

Replace the

circuit board

Replace

RELAY3

- PROBLEM (B) ­T.T. motor and oven lamp turn on When the door is
closed and START key is touched.

Measure the voltage at pin NO.
4 of U01
Voltage reading: 0 Vdc

Replace the

circuit board

Defective

RELAY3 or poor

connection of

RELAY3

Defective

RELAY3

Replace

RELAY3 or correct

the connection.

NO

NO

YES

YES

NO

NO

YES

YES

GOOD

7-20

NOTE: A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS

SERVICED FOR ANY REASON.

(3) CHECKOUT PROCEDURES FOR CIRCUIT

BOARD
The following symptoms indicate a defective circuit
board.

1) The start function fails to operate but the high
voltage Systems, the interlock switches, the door
sensing and the relay check good.

2) The unit with a normal relay continuously operates.

3) Proper temperature measurement is not obtained.

4) The buzzer does not sound or continues to sound.

5) Some segments of one or more digits do not light
up, or they continue to light up, or segments light
when they should not.

6) Wrong figures appear.

7) The figures of all digits.

8) Some of the indicators do no flicker light up.

9) The clock does not keep time properly.

7-21

PROBLEM - A: “PLEASE SET TIME OF DAY” does not appear in display window when power supply cord is

plugged into wall outlet.

PROBLEM - B: Display does not show correct numbers and/or

correct indications when programmed.

Check: 1. POWER SUPPLY

2. FUSE (See “CHECKOUT PROCEDURES FOR FUSE BLOWING: on page 7-18)

3. OVEN CAVITY THERMOSTAT

1

1

C. TROUBLE SHOOTING

Before following this troubleshooting read “TRIAL OPERATION” on page 6-1.

• “DISPLAY” Problems, “A” thru “C”

• “HELP UP” Problems, “D” thru “E” • “BUZZER Problems, “F”

WH

RD

Measure voltage between pin 1

and pin 3 of connector CN1.

Runs

Runs

Runs

Runs

Runs

0

120

Measure resistance of touch

key board after removing

connector S1.

(See page 7-4 and 7-17)

0

120

120V

Replace

circuit board

Normal

resistance

Voltage

incorrect

Normal

resistance

Resistance

incorrect

Replace touch

key board.

Normal touch

key board

Poor

contact

Correct

seating

Contact

ok

Replace

circuit board

Normal

circuit board

Normal

contact

Check contact

of connector S1

Correct

connections

Normal

circuit board

7-22

Resistance

incorrect

Check the continuity of

H.V.C. (see page 7-16)

Normal H.V.T.

Resistance

incorrect

Normal H.V.C.

Abnormal

Replace H.V.D.

Normal

Magnetron

Replace

Magnetron

Normal

Normal

H.V.D.

Check the

continuity of H.V.D.

(see page 7-16)

Replace H.V.C.

Normal

resistance

Replace H.V.T.

Normal

resistance

Runs

Runs

Runs

Contact

OK

Replace

circuit board

Normal

circuit board

Poor contact

Replace

circuit board

Normal

circuit board

Contact OK

Normal

contact

Correct

seating

Check contact of

connector S1

Check the contact of

relay 6(see page 7-18)

Measure resistance of

H.V.Transformer

(see page 7-15)

NO

continuity

PROBLEM - C: Unit does not heat up even if display counts down when

START key is touched for "HIGH POWER" cooking.

1

2

Check: 1. PRIMARY AND SECONDARY INTERLOCK SWITCHES

2.THERMOSTAT

7-23

PROBLEM - D: No buzzing when touching the key, between

stages or at end of cooking

1

Normal

circuit board

Check normal

operation

circuit board

Replace

circuit board

Runs

7-24

PROBLEM - E

:

Ventilation fan does not operate when “FAN HIGH/LOW” key is touched.

1

Check: 1. POWER SUPPLY

2. FUSE

Runs

Runs

Runs

Runs

Contact

OK

NO

contact

Replace

oven thermostat

Poor contact

Replace

circuit board

Normal

circuit board

Contact OK

Normal

contact

Correct

seating

Check contact

of connector S1

(see page 7-4)

Replace

ventilation

motor ASS’Y

NO runs

Normal

ventilation

motor ASS’Y

Check the contact of

oven thermostat

8-1

EXPLODED VIEW

DOOR

13581A

13552A

13536A

13213A

14890A

13720D

13650A

14970A

14026A

WTT028

8-2

CONTROL PANEL

24810P

23572A

23506A

*07

268711

24781M

WTP018

WTT029

8-3

OVEN CAVITY

36912C

63302A

WTT022

WTT028

WTT029

33112U

368771

WTT029

34810T

33530A

34890C

WTT022

35230A

63303A

34810Q

34960A

WTT021

*02

*01

*04

*05

535501

8-4

LATCH BOARD

466001

43500A

466003

466001

44510A

43501A

WSZ084

8-5

INTERIOR (I)

56170D

33390G

34370T

35889A

WTP013

WTT021

54810C

50CZZH

WSZ002

56851D

WTT021

WSZ002

33052A

56324A

WSZ002

53300A

WTT021

36549S

33740A

53300B

WTT021

WSZ098

8-6

INTERIOR (II)

55006F

36549V

56912B

53550L

55262A

55231C

56804A

WTT028

WSZ002

56930V

50FZZA

568771

56411A

8-7

INSTALLATION

WSZ133

44360A

WWZ068

63300M

65862D

65862B

WBZZ01

WSZ098

WWZ068

63861A

WBZZ02

WSZ136

8-12

SCHEMATIC DIAGRAM OF P.C.B

CUSTOM

SET

CLOCK

E

Z

On

KITCHEN

LEVEL

N.C

N.C

N.C

N.C

8-13

PRINTED CIRCUIT BOARD

P/NO : 3828W5S2380

July, 2002

Printed in Korea