Lg Lmh1517cvst Service Manual

MICROW AVE OVEN

SER VICE MANUAL

MODEL : LMH1517CVST

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

Website: http://us.lgservice.com

P/NO : 3828W5S2144

Feb. 2002

Printed in Korea

This device is to be serviced only by properly qualified service personnel.
Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be
taken to avoid possible exposure to excessive microwave energy.

PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE ENERGY

A) Do not operate or allow the oven to be operated with the door open.
B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other

microwave source, and make repairs as necessary; (1) interlock operation, (2) proper door closing, (3)
seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and
latches, (5) evidence of dropping or abuse.

C) Before turning on microwave power for any service test or inspection within the microwave generating

compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,
integrity, and connections.

D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation

and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual
before the oven is released to the owner.

E) A microwave leakage check to verify compliance with the Federal Performance Standard should be

performed on each oven prior to release to the owner.

SAFETY PRECAUTIONS

(Page)

SAFETY PRECAUTIONS

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Inside front cover

SPECIFICATIONS

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1-1

CAUTIONS

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2-1

INSTALLATIONS

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3-1

OPERATING INSTRUCTIONS

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4-1

FEATURES

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4-1

CONTROL PANEL

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4-1

OPERATING SEQUENCE

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4-2

SCHEMATIC DIAGRAM

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4-4

CIRCUIT DESCRIPTION

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4-5

SERVICE INFORMATION

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5-1

TOOLS AND MEASURING INSTRUMENTS

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5-1

MICROWAVE LEAKAGE TEST

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5-1

MEASUREMENT OF MICROWAVE POWER OUTPUT

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5-3

DISASSEMBLY AND ADJUSTMENT

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5-3

INTERLOCK CONTINUITY TEST

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5-8

COMPONENT TEST PROCEDURE

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5-9

TROUBLE SHOOTING

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5-13

EXPLODED VIEW

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6-1

REPLACEMENT PARTS LIST

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7-1

SCHEMATIC DIAGRAM OF P.C.B.

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8-1

PRINTED CIRCUIT BOARD

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8-2

P.C.B. PARTS LIST

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9-1

CONTENTS

1-1

This microwave oven is designed for household use only.
It is not recommended for commercial purposes.

ITEM

MODEL

Power Requirement

Power Output
Microwave Frequency
Magnetron
Timer
Outside Dimensions
Cavity Dimensions
Net Weight
Shipping weight
Control Complement

Accessories

DESCRIPTION

LMH1517CVST

120 Volts AC 60Hz
Single phase, 3 wire grounded
Microwave 1,500W
Convection 1,500W
Combination 1,500W

1,000W full microwave power(IEC60705)
2,450MHz
2M246
0~99min. 99sec.
22

5

/8“

(W) X 14

7

/8“

(H) X 20“(D)

15

1

/4“

(W) X 10

7

/8“

(H) X 15

1

/4“

(D)

52

lbs (approx.)

59

lbs (approx.)
Touch Control System
Clock : 1:00 - 12:59
Microwave Power for Variable Cooking
Power level

HIGH -------------------------------Full power throughout the cooking time
9 (Saute) -------------------------approx. 90% of Full power, 8 (Reheat) --------approx. 80%
7 (Med.-High)--------------------approx. 70%, 6 (Medium) --------approx. 60%
5 (Med.-Low) --------------------approx. 50%, 4 (Defrost)---------approx. 40%
3 (Low) ---------------------------approx. 30%, 2 (Simmer)---------approx. 20%
1 (Warm)--------------------------approx. 10%

• Convection - 100°F and 225°F to 450°F

• Combination

Owner's Manual
Glass Tray
Rotating Ring
Short Metal Rack

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 connected.
All input and output microwave connections,
waveguide, flange, and gasket must be
secured never operate the device without a
microwave energy absorbing load attached.
Never look into an open waveguide or antenna
while the device is energized.

GASKET

ANTENNA

COOLING FIN

MAGNETRON
CHASSIS GROUND

FILAMENT
TERMINALS

MAGNETRON

INSTALLATIONS

3-1

INSTALLING

1. Empty the microwave oven and clean inside it with
a soft, damp cloth. Check for damage such as
misaligned door, damage around the door, dents
inside the cavity, or on the exterior.

2. Put the oven on a counter, table, or shelf at least
100cm (39.4 inches) from floor that is strong
enough to hold the oven and the food and utensils
you put in it. (The control panel side of the oven is
the heavy side. Use care when handling.)

3. Do not block the vent and the air intake openings.
Blocking vent or air intake openings can cause
damage to the oven and poor cooking results.
Make sure the microwave oven legs are in place to
ensure proper air flow.

4. The oven should not be installed in any area where
heat and steam are generated, because they may
damage the electronic or mechanical parts of the unit.
Do not install the oven next to a conventional
surface unit or above a conventional wall oven.

5. Use microwave oven in an ambient temperature
less than 104°F(40°C).

6. Place the microwave oven on a sturdy and flat
surface at least 5cm (2 inches) from the wall.

7. Place the microwave oven as far away as possible
from TV, RADIO, COMPUTER, etc., to prevent
interference.

GROUNDING INSTRUCTIONS

For personal safety, this appliance must be fully
grounded at all times.

In the event of an electrical short circuit, grounding
reduces the risk of electrical shock.
The plug must be plugged into an outlet that is
properly installed and grounded.

BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.

WARNING

Improper use of the grounding plug can result in a
risk of electric shock.
Do not, under any circumstances, cut or remove
the third ground prong from the power cord plug.

PREFERRED METHOD

ENSURE PROPER GROUND

EXISTS BEFORE USE

Counter,

table, shelf

5cm

100cm

FEATURES

CONTROL PANEL

4-1

OPERATING INSTRUCTIONS

Short Metal Rack

Oven Front Plate

Window Door Screen

Door Seal

Safety Interlock
System

Control Panel

Display Window

Glass Tray
Rotating Ring

1. DISPLAY: The display includes a clock and indicators that tell
you time of day, cooking time settings, and cooking functions
selected.

2. CONVECTION : Touch this pad to cook Convection cooks.

3. COMBINATION : Touch this pad to cook Combination cooks.

4. MICROWAVE: Touch this pad to cook without entering a cook

power or time.

5. Q-DEFROST: Touch this pad to defrost foods quickly.

6. DEFROST AUTO/TIME: Touch this pad to defrost foods by

entering weight, or cook time.

7. MORE: Each time you touch this pad, you add 10 seconds to
the cooking time.

8. LESS: Each time you touch this pad, you subtract 10 seconds
from the cooking time.

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

10. NUMBER PADS: Touch number pads to enter cooking time,

power level, quantities, or weights.

11. TIME: Touch this pad to set a cooking time.

12. POWER. Touch this pad to set a cooking power.

13. CLEAR: Touch this pad to clear all entries.

14. EZ ON: Touch this pad to cook at 100% cook power for 1 to 99

minutes, 59 seconds.

15. START/PAUSE: Touch this pad to start all entries, or stop
cooking without opening the door.

16. HELP: Touch this pad to refer to feature information.

17. CUSTOM SET: Touch this pad to select Custom function.

18. HOLD WARM: Touch this pad to keep hot, cooked foods warm

in your microwave oven.

19. TIMER ON/OFF: Touch this pad to use your microwave oven
as a kitchen timer.

20. RECALL: Touch this pad to repeat cooking menu once more.

21. REMINDER: Touch this pad to use your oven like alarm clock.

1

2

3

4

7

10

11

13
14
16

19

65
8

9

12

15

17

18
20
21

OPERATING SEQUENCE

The following is a description of component functions
during oven operation.

1. SETTING THE CLOCK

2. CANCEL FUNCTION

1) Touch pad to start oven or pause the
oven temporarily during cooking.

2)

Touch pad to cancel a program during
cooking or Erase during programming.

3. TIMER ON/OFF

To cancel timer at any time, touch .

4. CHILD LOCK

TO SET CHILD LOCK

• Touch the pad.

• Touch and hold 0 pad LOCKED appear in

the display.

TO CANCEL CHILD LOCK

• Touch and hold 0 pad LOCKED disappear

in the display.

5. EZ ON

6. WARM HOLD

To keep hot, cooked food warm.

7. REMINDER

8. RECALL

To cook the same recipe repeatedly.

9. MORE/LESS

This pad is to be used as a temperature selection
pad in convection mode and cook time adjustment
pad in the microwave mode.

10. CUSTOM SET

You can select Sound Control, Clock On/Off,
Scroll, Speed, LBS°F/KG°C, Demo On/Off, and
English/Spanish.

• To turn off the clock.

11. TIMED COOKING

12. HELP

The help displays feature information and helpful
hints.

13. MULTI-STAGE COOKING

1ST STAGE

2ND STAGE

4-2

Clear Clock

Desired

clock

Start/Pause

Start/Pause

Timer On/Off

Clear

Clear

Custom

Set

2

2

Cook

Time

Cook

Power

Number

Power

Level

Start/Pause

Help

Feature

pad

Clear

Timer

On/Off

Desired

time

Timer

On/Off

Clear EZ On

Clear Recall

Clear

Reminder

Desired

Time

Reminder

Clear

Hold Warm

Start/Pause

Cook
Time

Cook

Power

Power

Level

Number

Cook
Time

Cook

Power

Number

Power

Level

Start/Pause

4-3

OPERATING SEQUENCE

14. SENSOR TOUCH

15. DEFROST AUTO/TIME

16. Q-DEFROST

17. AUTO BAKE/ROAST

18. CONVECTION

TO PREHEAT

TO COOK(After preheating)

19. COMBINATION

Clear

Sensor Cook/

Reheat

Select Recipe

Categories

Clear

Auto/Time

Defrost

Select Recipe

Categories

Enter the

Weight

Start/Pause

Clear

Auto Bake

Auto Roast

Categories

Start/Pause

Clear

Convection

Select

Temperature

Cooking Time

Start/Pause

Start/Pause

Enter the

Weight

Clear

Combi-Roast

Combi-Bake

Cooking Time

Start/Pause

Clear

Auto/Time

Defrost

Number

Start/Pause

Clear Q-Defrost

Select Recipe

Categories

Start/Pause

Clear Popcorn

SCHEMATIC DIAGRAM

4-4

IMPORTANT SAFETY NOTE: THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES

IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION, FIRE, ELECTRICAL SHOCK, AND

HAZARDS. WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER’S SPECIFIED PARTS

BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAGRAM.

NOTICE: SINCE THIS IS BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND

SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.

CIRCUIT DESCRIPTION

GENERAL DETAILS

• The low voltage transformer supplies the necessary
voltage to the micom controller when power cord is
plugged in.

• When the door is closed, the primary switch is ON, the
secondary switch is ON, and the monitor switch opens
(contact COM and NO).

WHEN SELECTING COOKING POWER
LEVEL AND TIME

• The micom controller memorizes the function you set.

• The time you set appears in the display window.

• Each indicator light turns on to indicate that the stage
has been set.

WHEN TOUCHING THE START PAD

• The coil of the relay is energized by the micom
controller.

• Power input is supplied to the high voltage transformer
through the fuse to the primary switch and relay 2.

• Turntable rotates.

• The fan motor rotates and cools the magnetron by
blowing the air.

• The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.

• Cooking time starts counting down.

• 3.15 volts AC is generated from the filament winding of
the high voltage transformer. This 3.15 volts is applied
to the magnetron to heat the magnetron filament
through two noise-preventing choke coils.

• A high voltage of approximately 2,210 volts AC is
generated in the secondary of the high voltage
transformer which is increased by the action of the high
voltage diode and charging of the high voltage
capacitor.

• The negative 4,000 Volts DC is applied to the filament
of the magnetron.

WHEN THE OVEN IS SET AT ANY LEVEL
EXCEPT MAXIMUM.

• The micom controller controls the ON-OFF time of relay
2 by the applied signal to vary the average output power
of microwave oven as

POWER LEVEL. (refer to page 1-1)

• One complete cycle of relay 2 is 22 seconds.

WHEN THE DOOR IS OPENED DURING
COOKING

• Both the primary switch and relay 2 cut off the primary
winding voltage of the high voltage transformer.

• ON-OFF of relay 2 is coupled electrically with opening
and closing of the secondary switch.

• When the door is opened, the secondary switch is
opened and when the door is closed, the secondary
switch is closed.

• The cooking time stops counting down.

• Relay stops functioning.

• As the door is opened, if the contact of primary switch
and relay2 and/or secondary switch fail to open, the
fuse opens due to the large current surge caused by the
monitor switch activation, which in turn stops magnetron
oscillation.

WHEN TOUCHING THE START KEY
WITH THE CONVECTION COOKING.

• The contacts of the primary switch and the secondary
switch close the circuit.

• Damper close.

• Turntable rotate.

• Fan Motor, Circulation Motor rotate.

4-5

L

FUSE

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY
SWITCH

PRIMARY

SWITCH

MONITOR

SWITCH

N

L

N

H.V.

TRANS-

FORMER

SECONDARY
SWITCH

FUSE

L

L

PRIMARY

SWITCH

RELAY 2

MONITOR

SWITCH

MICOM CONTROLLER

OVEN THERMOSTAT

N

G-Y

E

L

L

RELAY 4

CONVECTION

HEATER

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
Healthe 1390, Piccard Drive,
Rockville. MD 20850

• 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
5 mW/cm2. Always start measuring of an unknown field
to assure safety for operating personnel from radiation
leakage.

MEASURING MICROWAVE ENERGY
LEAKAGE

• Pour 275±15cc of 20±5°C(68±9°F) water in a beaker
which is graduated to 600 cc, and place the beaker
on the center of the turntable.

• Set the energy leakage monitor to 2,450 MHz and
use it following the manufacturer's recommended
test procedure to assure correct result.

• When measuring the leakage, always use the 2-inch
(5cm) spacer supplied with the probe.

• Operate the oven at its maximum output.

• Measure the microwave radiation using and
electromagnetic radiation monitor by holding the
probe perpendicular to the surface being measured

Move probe along shaded area

Probe scanning speed
Less than 2.5 cm/sec
( 1in/sec)

5-1

SERVICE INFORMATION

TOOLS AND MEASURING INSTRUMENTS

MICROWAVE LEAKAGE TEST

NECESSARY TOOLS

Tools normally used for TV servicing are sufficient.
Standard tools are listed below.

• Diagonal pliers

• Long nose pliers

• Phillips screwdriver

• Flat blade screwdriver

• Wrench (size 5mm)

• Nutdriver (size 5mm)

• Adjustable wrench

• Soldering iron

• Solder

• Vinyl insulation tape

• Polishing cloth

NECESSARY MEASURING INSTRUMENTS

• TESTER (VOLTS-DC, AC, Ohmmeter)

• Microwave survey meter

- Holaday HI-1500
HI-1501

- Narda 8100

8200

• Inch scale

• 600 cc non conductive material beaker (glass or plastic),
inside diameter: approx. 8.5 cm (3

1

/2

in.)

• Cylindrical and made of borosilicate glass vessel.
max. thickness: 3 mm
outside diameter: approx. 190mm
height: approx. 90mm

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

MEASUREMENT WITH OUTER CASE
REMOVED

• When you replace the magnetron, measure for
microwave energy leakage around the door view
window, the exhaust opening, and air inlet opening
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. (Circled area of Fig. below)

- Around the magnetron

- The waveguide

MEASUREMENT WITH A FULLY
ASSEMBLED OVEN

• After all components, including the outer case, are fully
assembled, measure for microwave energy leakage
around the door viewing window.

NOTES WHEN MEASURING

• Do not exceed meter full scale deflection.

• The test probe must be removed no faster than
1 inch/sec (2.5 cm/sec) along the shaded area,
otherwise a false reading may result.

• 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.

• 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

• 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.

• The microwave energy leakage should not be more than
5 mW/cm2. after determining that all parts are in good
condition, functioning properly and genuine replacement
parts which are listed in this manual have been used.

• At least once a year, have the electromagnetic energy
leakage monitor checked for calibration by its
manufacturer.

5-2

WARNING : AVOID CONTACTING ANY

HIGH VOLTAGE PARTS

• 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.

• The water is contained in a cylindrical borosilicate glass
vessel having a maximum material thickness of 3 mm
and an outside diameter of approximately 190mm.

• The oven and the empty vessel are at ambient
temperature prior to the start of the test.

• The initial temperature (T1) of the water is (10±2)°C 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.

• 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.

• The microwave power output P in watts is calculated
from the following formula :

• T2: Temperature after heating

• T

0

: Temperature of bowl

• M: Weight of bowl

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

•

The water is stirred to equalize temperature throughout
the vessel, prior to measuring the final water temperature

.

•

Stirring devices and measuring instruments are selected
in order to minimize addition or removal of heat

.

A. OUTER CASE REMOVAL

1) Disconnect the power supply cord from the outlet.

2) Remove the screws from the rear of the case.
The outer case must be moved backward to be lifted
off.

B. POWER SUPPLY CORD REMOVAL

1) Remove the outer case.

2) Disconnect two terminals, and remove one screw of the
ground terminal.

C. CONTROLLER ASSEMBLY REMOVAL

1) Open the door.

2) Remove the screws which hold the CONTROLLER
ASS’Y to the cavity and of the ground terminal.

3) Disconnect the leadwires from RELAY and connector
of the P.C.B. SUB ASS’Y.

4) Lift up and pull out CONTROLLER ASS’Y carefully
from the cavity.

CAUTION: DISCHARGE THE HIGH VOLTAGE

CAPACITOR BEFORE SERVICING

(refer to page 2-1)

5-3

WATER LOAD

TURNTABLE

MEASUREMENT OF MICROWAVE POWER OUTPUT

Remove the screw

Lift up and Pull out Controller ass’y

DISASSEMBLY AND ADJUSTMENT

4187 x (∆T) + 0.88 x (T2- T0) x M

T

P =

P.C.B ground

Key Pad ground

D. P.C.B. ASSEMBLY REMOVAL

1) Remove the control panel assembly from the cavity.
(Refer to control panel assembly removal on
previous page.)

2) Remove screws which hold the P.C.B. SUB ASS’Y
to the control panel.

3) Pull P.C.B. SUB ASS’Y carefully from the control
panel.

E. DOOR MAIN ASSEMBLY REMOVAL

1) Open the door.

2) Remove the choke cover very carefully with a flat-blade

screwdriver.

CAUTION: Be careful not to damage door seal plate by

screwdriver.

3) Lift up and pull the door.

NOTE:

1. After replacing the door, be sure to check that the

primary switch, monitor switch, and secondary switch
operate normally.

2. After replacing the door, check for microwave energy

leakage with a survey meter. Microwave energy must
be below the limit of 5 mW/cm2. (with a 275 ml water
load)

3. 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.

5-4

Door seal plate

Remove door

Remove choke cover

Spacer

Control Panel

PCB Sub Asm

Key

Membrane

5-5

F. AIR DUCT ASSEMBLY REMOVAL

1) Disconnect the leadwires from the lamp, micro
switch, damper motor, and damper switch.

2) Remove the screws holding the oven cavity and
latch board, air duct, and air tunnel ass’y.

3) Remove the mounting screws holding the
magnetron and air duct ass’y.

4) Remove air tunnel.

5) Pull latch board ass’y and air duct ass’y.

G. MAGNETRON REMOVAL

1) Remove the mounting screw holding the magnetron
and air duct ass’y.

2) Disconnect the leadwire from the magnetron.

3) Carefully remove the mounting screws holding the
magnetron and the waveguide.

4) Remove the magnetron from the waveguide.

NOTE:

1.

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

2. 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.

3. After replacing the magnetron, check for microwave
leakage with a survey meter around the magnetron.
Microwave energy must be below the limit of 5

mW/cm2. (With a 275 ml. water load).

Make sure that gasket is rigidly attached to the
magnetron. To prevent microwave leakage, tighten

the mounting screws properly, making sure there is
no gap between the waveguide and the magnetron.

Waveguide

Magnetron
Gasket

Magnetron

Dome
Waveguide

Bracket

Magnetron

Air Duct Ass’y

H. THE TURNTABLE MOTOR

REMOVAL

1) Remove the turntable and rotating ring.

2) Lay the unit down on its back.

3) Remove the turntable motor cover.
The turntable base cover is easily removed by
pinching the six parts with a wire cutting.

4) Disconnect the leadwire from the turntable motor
terminals.

5) Remove the screws securing the turntable motor to
the oven cavity ASS’Y.

6) After repairing the motor, rotate the removed
turntable motor cover.

7) Fit the turntable motor cover’s projecting part to the
base plate slit.

NOTE:

1. Remove the leadwire lead from the turntable motor

VERY CAREFULLY.

2. Be sure to grasp the connector, not the wires, when

removing.

I. HIGH VOLTAGE TRANSFORMER

REMOVAL

1) Discharge the high voltage capacitor.

2) Disconnect the leadwires from magnetron, and high
voltage capacitor.

3) Remove the screws holding the high voltage
transformer to the baseplate.

J. FAN MOTOR ASSEMBLY REMOVAL

1) Discharge the high voltage capacitor.

2) Disconnect the leadwires from fan motor, fuse holder,
and high voltage capacitor.

3) Remove the two screws holding the the suction guide
ASS’Y to the oven cavity and remove the high voltage
diode earth screw.

4) Remove the two screws holding the fan motor ASS’Y
to the suction guide ASS’Y.

K. HIGH VOLTAGE CAPACITOR AND

DIODE REMOVAL

1) Discharge the high voltage capacitor.

2) Disconnect the leadwires from fan motor, fuse holder,
and high voltage capacitor.

3) Remove the screw holding the suction guide ASS’Y to
the oven cavity and remove the high voltage diode
earth screw.

4) Remove the screw holding the high voltage capacitor
bracket.

5-6

H.V.
Transformer

Suction

Guide

Fuse Holder

Fuse

H.V.
Capacitor

Fan Motor
Ass’y

H.V Diode

H.V.C

Bracket

Wire

Leads

Turntable
Motor

L. INTERLOCK SYSTEM

1) 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.

2) MOUNTING OF THE PRIMARY/MONITOR/
SECONDARY SWITCHES TO THE LATCH
BOARD

3) INSTALLATION AND ADJUSTMENT OF THE
LATCH BOARD TO THE OVEN ASSEMBLY

• Mount the latch board to the oven assembly.

• Adjust the latch board in the arrow direction so that
oven door will not have any play in it when the door
is closed.

• Tighten the mounting screw.

• Check for play in the door by pulling and

pushing the door handle. Door movement
should be less than 0.5 mm. (1/64 inch)

Don't pull the door handle while making this
adjustment. Make sure that the latch moves
smoothly after adjustment is completed and that
the screws are tight. Make sure the primary,
monitor, and secondary switches operate properly
by following the continuity test procedure.

M. C-MOTOR, THERMISTOR AND

SHEATH HEATER REMOVAL

1) Remove back cover after untieing four screws
securing the cover assembly to the oven cavity.

2) Disconnect the leadwire from the circulation motor
and the sheath heater terminal.

3) Remove four hex nuts holding chamber ass’y to the
oven cavity.

4) Remove the screws of the thermistor, and lift up
chamber ass’y.

5) Remove a hex nut securing the circulation fan to
shaft of the C-motor.

6) Remove screws securing sheath heater to
chamber wall.

7) Remove sheath heater from chamber ass’y.

N. SENSOR

REMOVAL

1) Disconnect the sensor connector from P.C.B. Sub

Ass’y.

2) Remove the screw securing sensor to Air tunnel.

5-7

PRIMARY

SWITCH

SECONDARY

SWITCH

ADJUSTMENT

DIRECTION

MONITOR

SWITCH

A. PRIMARY INTERLOCK SWITCH TEST

When the door handle is depressed slowly with
the door closed, an audible click should be heard
at the same time or successively at intervals.
When the door handle is released slowly, 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 a
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 only 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 a open circuit in
the door open condition. When the door is closed,
meter should indicate an 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 closed circuit in
the door open condition. When the door is closed,
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.

5-8

WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION

EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS.

TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCH
TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH
TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF 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

COM

COM

NO

NC

NO

5-9

CAUTIONS

1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE
OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH
VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THE
HIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1)

2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1 LITER
OF WATER IN CONTAINER) IN THE OVEN.

COMPONENTS TEST PROCEDURE RESULTS

HIGH VOLTAGE
TRANSFORMER
(Wire leads removed)

MAGNETRON
(Wire leads removed)

1. Measure the resistance.
(Ohm-meter scale: Rx1 and Rx100)

• Primary winding

• Secondary winding

• Filament winding

2. Measure the resistance.
(Ohm-meter scale: Rx1000)

• Primary winding to ground

• Filament winding to ground

1. Measure the resistance.
(Ohm-meter scale: Rx1)

• Filament terminal

2. Measure the resistance.
(Ohm-meter scale: Rx1000)

• Filament to chassis

Approx.: 0.3 ~ 0.6 ohm
Approx.: 70 ~ 100 ohm
Less than: 1 ohm

Normal: Infinite
Normal: Infinite

Normal: Less than 1 ohm

Normal: Infinite

PRIMARY

TERMINAL

SECONDARY

FILAMENT
WINDING

COMPONENT TEST PROCEDURE

5-10

COMPONENTS TEST PROCEDURE RESULTS

HIGH VOLTAGE
CAPACITOR

HIGH VOLTAGE
DIODE

NOTE :
Some inexpensive meters
may indicate infinite
resistance in both direction.

Measure the resistance.
(Ohm-meter scale: Rx10,000)

• Terminal to terminal.

Measure the resistance.
(Ohm-meter scale: Rx10,000)

• Terminal to case.

Measure the continuity (Forward).
(Ohm-meter scale: Rx10000)

Measure the continuity (Reverse).
(Ohm-meter scale: Rx10000)

Normal: Momentarily indicates

several ohms, and
then gradually returns
to infinite.

Normal: Infinite.

Normal: Continuity.
Abnormal: Infinite.

Normal: Infinite.
Abnormal: Continuity.

NOTE: When testing the magnetron, be sure to install the magnetron gasket

in the correct position and be sure that the gasket is in good condition.

Antenna
Gasket

Chassis

Filament

5-11

COMPONENTS TEST PROCEDURE RESULTS

FUSE
(Wire leads removed.)

CONVECTION HEATER
(Wire leads removed)

MAGNETRON
THERMOSTAT

FAN MOTOR
(Wire leads removed)

Check for continuity of the switch with a
Multi-meter.

Measure the resistance.
(Multi-meter scale : R x 1)

Measure the resistance.
(Ohm-meter scale : R x 1)

Normal :
Approx. 9.5 ohm

(at 20~30°C)

Normal:
Approx. 49 ohm.

Abnormal: Infinite or several

ohm.

Normal Abnormal

Normal Abnormal

NOTE: If the fuse is blown, check the primary, the secondary, and the monitor

switches, H.V.D. and H.V.C. before replacing the fuse.
If the fuse is blown by improper switch operation replace the defective
switch and the fuse at the same time.
Replace just the fuse if the switches operate normally.

NOTE: Make sure heater is fully cooled when tested.

5-12

COMPONENTS TEST PROCEDURE RESULTS

CIRCULATION MOTOR
(Wire leads removed)

TURNTABLE MOTOR
(Wire leads removed)

DAMPER MOTOR
(Wire leads removed)

THERMISTOR
(Disconnect the 2 pin
connector from P.C.B.)

RELAY 2, 3, 4 OF P.C.B.
(leadwires removed.)
RY2 : Microwave
RY4 : Convection

Measure the resistance.
(Multi-meter scale : R x 1)

Measure the resistance.
(Ohm-meter scale : R x 1000)

Measure the resistance.
(Ohm-meter scale : R x 1000)

Normal : Approx. 29.5 ohm
Abnormal : Infinite or several

ohm.

Normal : Approx. 3.48 Kohm
Abnormal : Infinite or several

ohm.

Normal : Approx. 2.93 Kohm
Abnormal : Infinite or several

ohm.

Normal at room temperature
(20°C~30°C)

Approx. 255 Kohm

RY 4

RY 2

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

SERVICED FOR ANY REASON.
MAKE SURE THE WIRE LEADS ARE CORRECT POSITION.
WHEN REMOVING THE WIRE LEAD FROM THE PARTS, BE SURE TO GRASP THE
CONNECTOR, NOT THE WIRES.

Cooking Start OFF

TROUBLE SHOOTING

WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY. IF
THE FOLLOWING SYMPTOMS APPLY, PLEASE INSTRUCT THE CUSTOMER IN THE PROPER USE OF THE
MICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL.

5-13

CAUTIONS

1. Check grounding before checking for trouble.

2. Be careful of the high voltage circuit.

3. Discharge the high voltage capacitor. (See page 2-1)

4. When checking the continuity of the switches or of the high voltage transformer, disconnect one lead wire
from these parts and then check continuity with the AC plug removed. To do otherwise may result in a
false reading or damage to your meter.

5. Do not touch any part of the circuit on the P.C.B. since static electric discharge may damage this control
panel.

Always touch yourself to ground while working on this panel to discharge any static charge built up in your

body.

CONDITION

Microwave oven

does not work.

Inserting many plugs into one
outlet and using them at the
same time.
(blown fuse or breaker)

Microwave oven plug is not
inserted tightly.

Output power is too low. Low AC input voltage.

Food temperature is too low.

Using metallic ware and
allowing it to touch the oven
wall.

Sparks occur.

Inconsistent intensity of
microwave by their
characteristics.

1. Use plastic wrap or lid.

2. Stir once or twice while
cooking soup, cocoa or
milk, etc.

Uneven cooking.

Ceramic ware trimmed in
gold or silver powder is used.

Avoid using other electrical
appliances when you use the
microwave oven.

Insert microwave oven plug
securely.

Use the microwave oven at
adequate line voltage.

This may not be a defect.
It is possible that the food
should be cooked for a
longer time period.

Do not use metallic ware for
cooking except that noted in
the cooking guide.

Do not use any type of
cookware with metallic
trimming.

CAUSE REMEDY

1. Incomplete segments.

• Segment missing.

• Partial segment missing.

• Digit flickering (NOTE: Slight flickering is normal.)

2. Colon does not turn on or blink.

3. A distinct change in the brightness of one or more numbers in display.

4. One or more digits in the display are not lighting.

5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.

6. Specific numbers (for example 7 or 9) does not display when key pad is touched.

7. Display does not count down with time blinking or up with clock operation.

8. Display obviously jumps in time while counting down.

9. Display counts down too fast while cooking.

10. Each indicator light does not turn on after setting cooking cycle.

11. Display time of day does not reappear when cooking is finished.

5-14

(TROUBLE 1)

The following visual conditions indicate a probable defective control circuit.

CONDITION CHECK RESULT CAUSE REMEDY

1. No input can be
programmed.

Continuity

No continuity

Defective P.C.B.
assembly.

Loose
connection.

Replace P.C.B.
assembly.

Connect them
tightly.

Check the conn­ection between
membrane key
assembly and
P.C.B.

assembly.

2. Some inputs
cannot be
programmed.

3. Display shows a
number or figure
different from one
touched.

4. Random
programming
when touching
other pads.

5. Display is fixed
at some figure
and can not
accept any
input.

Everything works
as specified.

Still have trouble.

Defective key
membrane
assembly.

Defective P.C.B.
assembly.

Replace key
membrane
assembly.

Replace P.C.B.
assembly.

Replace key
membrane
assembly and
check operation.

5-15

CONDITION CHECK RESULT CAUSE REMEDY

1. Fuse blows. Continuity.

No continuity.

Continuity.

Shorted contact at
the primary switch.

Replace fuse,
primary, monitor,
secondary
switches, and
RELAY(RY2) of
P.C.B. Assembly.

No continuity.

Normal.

Defective high
voltage capacitor.

Replace high
voltage capacitor.

Fuse blows again

Defective high volt­age transformer.

Replace high volt­age transformer.

Malfunction of the
monitor switch.

Replace fuse,
primary, monitor,
secondary
switches, and
RELAY(RY2) of
P.C.B. Assembly.

Check continuity
of monitor
switch (with
door closed).

Check continuity
of primary
switch (with
door opened).

Disconnect one
side of the wire
lead connected
from transformer
to the high
voltage
capacitor and
operate the unit.

Replace fuse

Continuity.

Malfunction of
secondary switch.

Replace fuse,
primary, monitor,
secondary
switches, and
RELAY(RY2) of
P.C.B. Assembly.

No continuity.

Check continuity
of secondary
switch (with
door opened).

2. Fuse does not

blow.

No continuity.

Continuity.

No continuity.

Defective power
supply cord.

Replace power
supply cord.

Defective
thermostat.

Replace
thermostat.

Check continuity
of thermostat.

Check continuity
of power supply
cord.

(TROUBLE 2)

Oven does not operate at all, display window does not display any figures,
and no input is accepted.

NOTE : All these switches must be replaced at the same time. Refer to page 5-7, 5-8

5-16

CONDITION CHECK RESULT CAUSE REMEDY

1.

Setting time does
not count down
when touching
START pad.

2. Fan motor or
oven lamp do
not turn on.

No continuity.

Continuity.

Continuity

Defective P.C.B.
assembly.

Loose connection.

Replace P.C.B.
assembly.

Connect them
tightly.

No continuity

Abnormal

Check fan motor.

Defective fan motor. Replace fan motor.

Abnormal

Normal

No continuity
Continuity

Check oven lamp.

Check continuity
of primary switch.

Defective oven lamp. Replace oven lamp.

Defective
secondary switch.

Replace
secondary switch.

Check continuity
of secondary
switch (with
door closed).

Check the con­nection between
CN1 connector
and P.C.B.
assembly.

Defective primary switch. Replace primary switch.

(TROUBLE 3)

Display shows all figures set, but oven does not start cooking while desired

program times are set and START pad is touched.

(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.

NOTE :

Simple test of power output-conducted by heating one liter water for one min. if available.

Minimum 8.5°C temperature rise is normal condition.

CONDITION CHECK RESULT CAUSE REMEDY

Output is low

Lower than 90% of
rating voltage.

Normal

Abnormal

Defective P.C.B.
assembly.

Replace P.C.B.
assembly.

Normal

Abnormal

Measure the
output power.

Defective
magnetron.

Replace
magnetron.

Decrease in power
source voltage with
load.

Suggest customer
contact local electric
power utility co. or
qualified electrician.

Check the
power source
voltage.

Disconnect the
wire leads from
relay 2 and
check on and off
time with
multitester.

5-17

CONDITION CHECK RESULT CAUSE REMEDY

No microwave
oscillation.

No continuity.

Continuity.

Abnormal

Defective high
voltage
transformer.

Replace high
voltage
transformer.

Normal

Defective P.C.B.
assembly.

Replace P.C.B.
assembly.

Disconnect the
wire leads from
relay 2 and
check continuity
of relay 2.
(Operate the unit)

Check high vol­tage transformer

Output is full power
when you set lower
power level.

Abnormal.

Defective P.C.B.
assembly.

Replace P.C.B.
assembly.

Disconnect the
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)

Abnormal

Defective high
voltage capacitor.

Replace high
voltage capacitor.

Normal

Check high vol­tage capacitor.

Abnormal

Defective high
voltage diode.

Replace high
voltage diode.

Normal

Check high vol­tage diode.

Abnormal

Defective
magnetron.

Replace
magnetron.

Check
magnetron.

(TROUBLE 5)

No microwave oven operation even though oven lamp and fan motor run.

(Display operates properly)

NOTE : • Make sure the wire leads correct position.

• When Removing the wire leads from the parts, be sure to grasp the connector, not the wires.

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

5-18

(TROUBLE 6) Convection oven does not operate at all or convection cook

is bad.

CONDITION CHECK RESULT CAUSE REMEDY

Temperature in
the oven cavity is
lower or higher
than preset.

Abnormal
Normal

Defective Relay
4 or 6.

Replace
Relay 4 or 6.

Check the Relay
4 or 6 of P.C.B.
assembly .

Abnormal
Normal

Defective
convection heater.

Replace
convection heater.

Check the
convection heater
element.

Abnormal
Normal

Defective
circulation motor.

Replace
circulation motor.

Check the
circulation motor.

Abnormal
Normal

Defective
damper motor.

Replace
damper motor.

Check the
damper motor.

Interference
Damper open
and close at air
duct assembly.

Normal

Defective air
duct assembly.

Replace air duct
assembly.

Check the air
duct assembly.

Error message
shows in the display.

Normal

Thermistor open
or short.

Replay
thermistor.

Check the
thermistor.

Cook on the
glass tray.

Without
metal rack.

Cook with
metal rack.

Check the Rack.

Convection indicator
light but oven does
not go into cook
cycle when START
pad is touched.

Abnormal

Normal

No continuity.

Loose connection.

Connect them
tightly.

Defective Relay
4 or 6.

Replace Relay
4 or 6.

Check the Relay
4 or 6 of P.C.B.
assembly .

Check the
connection between
P.C.B.

assembly and

headwire connector.

DOOR PARTS

CONTROL PANEL PARTS

BASE PARTS

INTERIOR PARTS

OVEN CAVITY PARTS

LATCH BOARD PARTS

6-1

EXPLODED VIEW

INTRODUCTION

MODEL : LMH1517CVST

#EV#

6-2

13581A

13552A

13213A

14890A

14970A

14026A

WTP

013

15006A

DOOR PARTS

#EV#

13551A

13650A

6-3

24781M

23551A

268711

WTP018

CONTROLLER PARTS

#EV#

6-4

33112U

WTT021

WSZ185

WMT002

WNH002

WTT020

WTT011

WTT020

35026G

33390G

35889A

WTP

013

36549S

34370T

33052M

948502

OVEN CAVITY PARTS

#EV#

6-5

WSZ085

43500A

43501A

466001

44510A

466003

466001

WTP

007

466001

WTT

028

WTT

028

WTP

013

56912B

55262A

53550L

54810U

36549W

LATCH BOARD PARTS

#EV#

6-6

WSZ085

WSZ185

WTT021

WSZ002

568771

56324A

WSZ002

WTT028

56851D

WSZ

002

54810C

50CZZH

50FZZA

55900N

54810S

56322A

WTT022

56411A

53504A

53300G

348102

35300S

55900C

343501

34930R

WTT022

56549C

56820A

56549F

54974S

55900A

WTT

037

WTP

015

WNH

002

WSZ059

WNH

003

WWP008

WWS005

568772

33808A

WMT

002

34930W

INTERIOR PARTS

#EV#

348101

348103

55290A

6-7

63303A

56170D

63302A

65006B

WTT021

WSZ002

BASE PLATE PARTS

#EV#

6-8

56501A

35264A

56930M

WTT021

WTP002

SENSOR PARTS

#EV#

8-1

SCHEMATIC DIAGRAM OF P.C.B.

8-2

PRINTED CIRCUIT BOARD