LG LPC-M140A, LPC-M140X Service Manual

MODEL: LPC-M140A/X

SERVICE MANUAL

P/NO : 3829RGT008F OCTOBER, 2007

PORTABLE CD
CASSETTE RECORDER

SERVICE MANUAL

MODEL: LPC-M140A/X

Website http://biz.lgservice.com

Internal Use Only

This S/M developed for the SVC of the unit which is indicated with
the “SVC Model No. : LPC-M140N” in the Main Label.

NOTICE

- 1-1 -

Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

LGE Internal Use Only

[CONTENTS]

❍ SECTION 1.GENERAL

• SERVICING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

• ESD PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

• SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5

• IDENTIFICATIONS OFCONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

❍ SECTION 2.ELECTRICAL SECTION

• ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

• TROUBLESHOOTING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

• INTERAL BLOCK DIAGRAM OF ICs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

• IC/TR VOLTAGE & PIN DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

• BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19

• SCHEMATIC DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

• WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-27

• PRINTED CIRCUIT BOARD DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

❍ SECTION 3. EXPLODED VIEWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

❍ SECTION 4. REPLACEMENT PARTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

- 1-2 -

Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

LGE Internal Use Only

SECTION 1. GENERAL

❏ SERVICING PRECAUTIONS

NOTES REGARDING HANDLING OF THE PICK-UP

1. Notes for transport and storage

1) The pick-up should always be left in its conductive bag until immediately prior to use.

2) The pick-up should never be subjected to external pressure or impact.

2. Repair notes

1) The pick-up incorporates a strong magnet, and so should never be brought close to magnetic materials.

2) The pick-up should always be handled correctly and carefully, taking care to avoid external pressure and
impact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/or
damage to the printed-circuit board.

3) Each and every pick-up is already individually adjusted to a high degree of precision, and for that reason
the adjustment point and installation screws should absolutely never be touched.

4) Laser beams may damage the eyes!
Absolutely never permit laser beams to enter the eyes!
Also NEVER switch ON the power to the laser output part (lens, etc.) of the pick-up if it is damaged.

5) Cleaning the lens surface
If there is dust on the lens surface, the dust should be cleaned away by using an air bush (such as used
for camera lens). The lens is held by a delicate spring. When cleaning the lens surface, therefore, a cotton
swab should be used, taking care not to distort this.

6) Never attempt to disassemble the pick-up.
Spring by excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab. (Do
not use any other liquid cleaners, because they will damage the lens.) Take care not to use too much of
this alcohol on the swab, and do not allow the alcohol to get inside the pick-up.

Storage in conductive bag

Drop impact

NEVER look directly at the laser beam, and don’t let
contact fingers or other exposed skin.

Magnet

How to hold the pick-up

Conductive Sheet

Cotton swab

Pressure

Pressure

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Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

LGE Internal Use Only

NOTES REGARDING COMPACT DISC PLAYER REPAIRS

1. Preparations

1) Compact disc players incorporate a great many ICs as well as the pick-up (laser diode). These components
are sensitive to, and easily affected by, static electricity. If such static electricity is high voltage, components
can be damaged, and for that reason components should be handled with care.

2) The pick-up is composed of many optical components and other high-precision components. Care must be
taken, therefore, to avoid repair or storage where the temperature of humidity is high, where strong magnet­ism is present, or where there is excessive dust.

2. Notes for repair

1) Before replacing a component part, first disconnect the power supply lead wire from the unit

2) All equipment, measuring instruments and tools must be grounded.

3) The workbench should be covered with a conductive sheet and grounded.
When removing the laser pick-up from its conductive bag, do not place the pick-up on the bag. (This is
because there is the possibility of damage by static electricity.)

4) To prevent AC leakage, the metal part of the soldering iron should be grounded.

5) Workers should be grounded by an armband (1M Ω)

6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent sta­tic electricity changes in the clothing to escape from the armband.

7) The laser beam from the pick-up should NEVER be directly facing the eyes or bare skin.

Resistor
(1 Mohm)

Conductive
Sheet

Resistor
(1 Mohm)

Armband

- 1-4 -

Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

LGE Internal Use Only

❏ ESD PRECAUTIONS

Electrostatically Sensitive Devices (ESD)

Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components
commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated
circuits and some field-effect transistors and semiconductor chip components. The following techniques should
be used to help reduce the incidence of component damage caused by static electricity.

1. Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off

any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a
commercially available discharging wrist strap device, which should be removed for potential shock reasons
prior to applying power to the unit under test.

2. After removing an electrical assembly equipped with ESD devices, place the assembly on a conductive sur-

face such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.

3. Use only a grounded-tip soldering iron to solder or unsolder ESD devices.

4. Use only an anti-static solder removal device. Some solder removal devices not classified as "anti-static" can

generate electrical charges sufficient to damage ESD devices.

5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ESD

devices.

6. Do not remove a replacement ESD device from its protective package until immediately before you are

ready to install it. (Most replacement ESD devices are packaged with leads electrically shorted together by
conductive foam, aluminum foil or comparable conductive materials).

7. Immediately before removing the protective material from the leads of a replacement ESD device, touch the

protective material to the chassis or circuit assembly into which the device will by installed.

CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL

OTHER SAFETY PRECAUTIONS.

8. Minimize bodily motions when handing unpackaged replacement ESD devices. (Otherwise harmless motion

such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can gen­erate static electricity sufficient to damage an ESD device).

CAUTION. GRAPHIC SYMBOLS

THE LIGHTNING FLASH WITH APROWHEAD SYMBOL. WITHIN AN EQUILATERAL TRIANGLE, IS
INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF UNINSULATED “DAN­GEROUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAGNITUDE TO CONSTITUTE A RISK OF
ELECTRIC SHOCK.

THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE
SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE
LITERATURE.

- 1-5 -

Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

LGE Internal Use Only

❏ SPECIFICATIONS

[General]

[CD]

[Tuner]

AM

FM

(MW)

[

TAPE

]

Power supply Refer to the back panel of the unit.

Power consumption 10W
Mass kg
External dimensions (W x H x D) 300 x 252 x 171 mm
Output Power 1W X 2 T.H.D 10%
Speakers 8Ω X 2
Battery Operation DC 9V, six "C"(R14) batteries (not supplied)
Frequency response 100 - 18000 Hz
Signal-to-noise ratio 55 dB
T.H.D %
Tuning Range 87.5 -108 MHz 87.5 -108 MHz/65 -108 MHz
Intermediate Frequency 10.7 MHz
Antenna Telescopic antenna
Tuning Range 522-1620KHz or 530-1720KHz
Intermediate Frequency 455 kHz
Antenna Ferrite bar antenna
Recording System 4 Tracks 2 channel stereo
Frequency Response 125 - 8000Hz
Signal to Noise Ratio 35/40dB (REC/PLAY)

Designs and specifications are subject to change without notice for improvement.

LPC-M140A

MODEL

SECTION

LPC-M140X

0.5

3.0

- 1-6 -

Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

LGE Internal Use Only

❏ IDENTIFICATIONS OF CONTROLS

1

2

3

4

5

6

7

5

8

11

12

Up Panel

Front Panel

9

10

UP Panel/Front Panel

1.CD DOOR

2.FUNCTION SWITCH

[CD/FM/AM/TAPE ]

3.VOLUME CONTROL DIAL

4.DISPLAY WINDOW indicator

5.LEFT/RIGHT SPEAKER

6.TAPE DOOR

7.CD FUNCTION buttons

• CD BACKWARD SKIP//SEARCH ( )
button

• +10 BUTTON

• CD FORWARD SKIP//SEARCH ( )

button

• CD REPEAT button

• CD STOP (■)button

• CD PLAY//PAUSE ( ) button

8.TAPE FUNCTION buttons

• TAPE PAUSE (II) button

•TAPE STOP/EJECT( ) button

• FAST FORWARD ( )button

• REWIND ( )button

• TAPE PLAY ( )button

• RECORD (●)button

9.CD DOOR OPEN ( OPEN)button

10.STEREO indicator

11.TUNING DIAL

12.FREQUENCY indicator

- 1-7 -

Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

LGE Internal Use Only

Rear Panel/Display Window

1

2

3

4

5
6

Rear Panel

Display Window

1. FM ANTENNA

2. RIF/FM MODE SWITCH (ST./MONO)
HEADPHONE SOCKET ( ): 3.5mm

3. AC POWER INPUT SOCKET

4. CD REPEAT PLAY indicator

5. CD PLAY indicator

6. CD PAUSE indicator

7. CD TRACK NUMBER indicator

8. CD SYNCHRONIZED RECORDING indicator

7

8

- 1-8 -

Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

LGE Internal Use Only

- 2-1 -

Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

LGE Internal Use Only

SECTION 2. ELECTRICAL

❏ ADJUSTMENTS

1. FM/AM ADJUSTMENT

NO ITEM INPUT POINT OUTPUT POINT SPECIFICATION ADJUSTING POINT ADJUST FOR

1 AM IF L108 IC101 PIN18 455kHz L102 GAIN MAXIMUM

2 AM COVER

LOW L108 IC101 PIN18 515kHz L101 Repeat several times
HI L108 IC101 PIN18 1650kHz TC3

3

AM TRACKING

LOW L108 IC101 PIN18 600kHz L108 GAIN MAXIMUM
HI L108 IC101 PIN18 1400kHz TC4

4 FM COVER

LOW C101 IC101 PIN18 87.00MHz L104 Repeat several times
HI C101 IC101 PIN18 108.5MHz TC2

5 FM TRACKING

LOW C101 IC101 PIN18 90MHz L103 GAIN MAXIMUM
HI C101 IC101 PIN18 106MHz TC1

2. TAPE DECK ADJUSTMENT

NO ITEM OUTPUT POINT SPECIFICATION ADJUSTING POINT ADJUST FOR

1 TAPE SPEED NOR MTT-111N 3000±90Hz NON
2 AZIMUTH ADJUST MTT114

DECK MECHA ADJ. HOLE

GAIN MAXIMUM

3 RECORDING BIAS 55kHz±500Hz L203