LG MCV903 Diagram

MODEL : MCV903(MCS903F,MCS903S,MCS903W,MCS903AW)

SERVICE MANUAL

MINI Hi-Fi SYSTEM

SERVICE MANUAL

CAUTION

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

MODEL : MCV903

(MCS903F,MCS903S,MCS903W,MCS903AW)

Website http://biz.lgservice.com

Internal Use Only

LGE Internal Use Only

1-1

❍ SECTION 1. GENERAL

•

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

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

• LOCATION OF USERS CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

• SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

• USB DOWNLOAD GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

❍ SECTION 2. EXPLODED VIEWS

•

CABINET AND MAIN FRAME SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

• TAPE DECK MECHANISM EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

• CD MECHANISM EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

•

SPEAKER EXPLODED VIEW. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

• PACKING ACCESSORY

VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

❍ SECTION 3. AUDIO ELECTRICAL PART

•

AUDIO ELECTICAL TROUBLESHOOTING GUIDE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

• INTERNAL BLOCK DIAGRAM OF ICs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

• WIRING DIAGRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-29

• BLOCK DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31

• SCHEMATIC DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-35

• PRINTED CIRCUIT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59

❍ SECTION 4.

CD

ELECTRICAL PART

•

CD ELECTICAL TROUBLESHOOTING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

• WAVEFORMS OF MAJOR CHECK POINT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

• SCHEMATIC DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

• PRINTED CIRCUIT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

❍ SECTION 5. REPLACEMENT PARTS LIST

•

REPLACEMENT PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

[CONTENTS]

1-2

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.

SERVICING PRECAUTIONS

SECTION 1. GENERAL

Only for training and service purposes

LGE Internal Use Only

1-3

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 (1MΩ)

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.

CLEARING MALFUNCTION

You can reset your unit to initial status if malfunction occur(button malfunction, display, etc.). Using a pointed good conductor(such as driver), simply short the RESET jump wire on the inside of the volume knob for more than 3 seconds. If you reset your unit, you must reenter all its settings(stations, clock, timer)

NOTE: 1. To operate the RESET jump wire, pull the volume rotary knob and release it.

2. If you wish to operate the RESET jump wire, it is necessary to unplug the power cord.

Only for training and service purposes

LGE Internal Use Only

1-4

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 surface 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

ESD PRECAUTIONS

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

LGE Internal Use Only

LOCATION OF USERS CONTROLS

FRONT / BACK PANEL

• DISPLAY WINDOW

• Choose a desired CD

• TIME

• Power on/off

• CLOCK

•

To select TUNER (FM or AM) fuction

• eXtreme Dynamic Sound System

• Look for radio stations automatically

• DEMO

• VOCAL FADE

• PORTABLE IN

• PHONES

• SET

•



OPEN/CLOSE

• Record from tape to tape

• Disc tray

• Skip to another track

• NATURAL EQ

• MIC VOL.

• Starts playback

• Stops playback or recording

• Look for radio stations

automatically

• Starts or pauses recording

• PORTABLE

• MIC 1/MIC 2

1-6

Only for training and service purposes

LGE Internal Use Only

REMOTE CONTROL

• NATURAL EQ

You can choose sound impressions.

• Power on/off Power save mode

Press POWER for longer than 3 seconds as the device is powered on, you can move into power save mode.

• Search for a folder of MP3/WMA files

When a CD containing MP3/WMA files in several fold-ers is being played, press PRESET/FOLDER to select the folder you want to play.

Choose a ‘preset number’ for a radio station

(see Listening to the radio)

• Listen to your tracks again and again

• Fall asleep while listening to your player

Press SLEEP one or more times to select delay time between 10 and 180 minutes, after the player will turn off.

Dimm the display light

• For storing radio stations

(see Listening to the radio)

Listen to your tracks in any order

(see Listening to the CDs)

• Choose a desired CD

(see Listening to CDs)

• Selecting the sound system

You can enjoy different sounds by selecting the sound mode you want. Press LINK repeatedly, the display changes in the following order, LINK ON→SURROUND 1→SURROUND 2.

• VSM (Virtual Sound Matrix)

You can select the Virtual sound.

• Temporarily stop the sound

Press the button again to return to the sound.

• To change the functions

Change the functions among FM, AM, CD, TAPE.

• Control the volume when using any function.

• To change the INPUT functions

Change the functions among USB, PORTABLE, AUX.

• See information about your music

MP3/WMA files often come with tags. The tag gives the Title, Artist, Album or Time information.

• Stops playback or recording

• Starts or pauses recording

• Starts or pauses playback Improve poor FM reception

This will change the tuner from stereo to mono and usually improve

the reception

• Select the radio station Search for a section within a track Play Fast backward or Forward

.

1-7

LGE Internal Use Only

SPECIFICATIONS

General

Power supply Refer to main label. Power consumption Refer to main label. Net Weight 8.45 kg External dimensions (W x H x D) 170 x 240 x 260 mm Operating temperature 5ºC to 35ºC Operating humidity 5% to 85 %

Tuner

FM Tuning Range 87.5 - 108.0 MHz or 65.0 - 74.0 MHz, 87.5 - 108.0 MHz AM Tuning Range 522 - 1,620 kHz or 520 - 1,720 kHz

Amplifier

OUTPUT POWER Front : 280 W + 280 W, Surround : 140 W + 140 W,

Sub Woofer : 180 W + 180 W T.H.D 10 % Frequency Response 40 - 20000Hz Signal-to-noise ratio 75dB

CD player

Frequency response 42 - 20000 Hz Signal- to- noise ratio 75 dB Dynamic range 80dB

Cassette tape player

F.F/REW Time 120 sec (C-60) Frequency Response 250 - 8000 Hz Signal to Noise Ratio 43 dB Channel Separation 45 dB (P/B)/45 dB (R/P) Erase Ratio 50 dB (MTT-5511)

Speakers

MCS903S MCS903F MCS903AW/MCS903W

Type

Bass Reflex 2Way 2 Speaker Bass Reflex 2Way 2 Speaker Bass Reflex 1 Way 1 Speaker Impedance 16 Ω 8 Ω 12 Ω Frequency Response 70 - 20000 Hz 55 - 20000 Hz 50 - 1500 Hz Sound Pressure Level Rated

83 dB/W (1m) 86 dB/W (1m) 85 dB/W (1m) Input Power 140 W 280 W 180 W Max. Input Power 280 W 560 W 360 W Net Dimensions 205 x 432 x 286 mm 270 x 432 x 326 mm 315 x 432 x 356 mm Net Weight (1EA) 4.4 kg 8.3 kg 9.8 kg

Designs and specifications are subject to change without pior notice.

1-8

Only for training and service purposes

LGE Internal Use Only

USB DOWNLOAD GUIDE

1. AUDIO USB DOWNLOAD GUIDE

Download program file name must be MCV903.HEX.mcs.

→ If security program (Water Wall) is activated on your PC, you must save the file to the USB storage

device and disable the security software then download the file to your set.

Caution: When downloading the file, you should neither unplug the USB device, change to the other

function, nor power off the device. USB device must be unplugged when the downloading process is completed.

ON VFD DISPLAY SCREEN

NO USB

1. INSERT USB DEVICE AT USB FUNCTION

2. WHEN COMPLETED, REMOVE USB DEVICE.

READ

FIRMWARE

WRITE 00 .. 100

UPDATED

POWER OFF AUTOMATICALLY

1-9

LGE Internal Use Only

2. CD USB DOWNLOAD GUIDE

Download program file name must be LGBOX_HA8M.mcs.

→ If security program (Water Wall) is activated on your PC, you must save the file to the USB storage

device and disable the security software then download the file to your set.

Caution: When downloading the file, you should neither unplug the USB device, change to the other

function, nor power off the device. USB device must be unplugged when the downloading process is completed.

ON VFD DISPLAY SCREEN

NO USB

1. INSERT USB DEVICE AT USB FUNCTION

2. WHEN COMPLETED, REMOVE USB DEVICE.

READ

FIRMWARE

FINISH

UPDATED

POWER OFF MANUALLY

1-10

Only for training and service purposes

LGE Internal Use Only

2-1 2-2

1. CABINET AND MAIN FRAME SECTION

SECTION 2. EXPLODED VIEWS

NOTES) THE EXCLAMATION POINT WITHIN AN

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

A43

CABLE3

270

FRONT

H

A00

265

274

451

288

259

CABLE1

260

451

274

271

F

CABLE2

289

G

A46

451

250

H

F

451

266

265

A47

D

A26

275

C

B

A

CD

D

L

A

272

451

A51

K

CABLE4

J

451

302

453

I

K

AIN

M

C

B

A41

280

451

283

453

L

G

SMPS

451

283

278

301

E

A56

451

E

305

276

451

262

I

285

277

281

451

SUB

A52

J

282

2-3 2-4

Only for training and service purposes

LGE Internal Use Only

TAPE DECK MECHANISM EXPLODED VIEW

1. TAPE DECK MECHANISM (A/R & A/S : RIGHT A/R DECK)

009

A00

001

003

BRASS MOTOR PULLEY MAYBE CHANGED FOR WOW FLUTTER WHEN NECESSAR

002

Y

006

037

007

008

016

015

022

RING FW MAYBE ADDED FOR WOW FLUTTER WHEN NECESSAR

019

018

017

023

025

Y

020

A01

011

009

013

A02

RING FW MAYBE ADDED FOR WOW FLUTTER WHEN NECESSAR

Y

2. TAPE DECK MECHANISM (A/R & A/S : LEFT A/S DECK)

2-5 2-6

LGE Internal Use Only

019

003

009

A00

007

008

016

017

022

018

023

015

020

RING FW MAYBE ADDED FOR WOW FLUTTER WHEN NECESSAR

024

Y

011

009

013

A03

CD MECHANISM EXPLODED VIEW

2-7 2-8

Only for training and service purposes

LGE Internal Use Only

159

416

A26

151

A32

416

177

166

417

167

165

164

417

422

440

441

172

163

170

419

168

155

417

162

153

173

418

421

156

A35

188

189

190

418

181

A30

421

184

187

175

186

185

417

2-9

LGE Internal Use Only

• FRONT SPEAKER (MCS903F)

SPEAKER EXPLODED VIEW

A80L

A80R

A80BL

A80BR

858

A80A

852

854

853

851

850

856

855

857

WIRE80

WIRE81

860

859

860

2-10

Only for training and service purposes

LGE Internal Use Only

• REAR SPEAKER (MCS903S)

A60R

A60A

653

A60BL

A60BR

WIRE60

WIRE61

654

651

650

652

655

656

657

658

2-11

LGE Internal Use Only

• PASSIVE SUBWOOFER (MCS903W)

952

953

950

A90

951

958

956

957

A90B

A90A

954

955

2-12

Only for training and service purposes

LGE Internal Use Only

• PASSIVE SUBWOOFER (MCS903AW)

A70B

A70

761

753

752

A70A

750

751

754

755

757

756

758

759

760

WIRE70

762

2-13

LGE Internal Use Only

• PACKING ACCESSORY

VIEW

824 ANTENNA LOOP

825 ANTENNA

808 Battery

OPTIONAL PARTS

806 Cable, Coaxial

811

Plug Ass'y, 1Way

Plug Ass'y, 2Way(Yellow)

812

Remote Control

900

Instruction Ass'y

801

803

Packing

Bag

804

826 Microphone

832

DISC

830 AC Adaptor

803

Packing

Box

802

2-14

Only for training and service purposes

LGE Internal Use Only

3-1

LGE Internal Use Only

1. MICOM PART CHECK I

OK OK

NO

NO NO

Replace the related

part

Is IC101 KIA7042

output 4.3V?

YES

YES YES

Check the IC100

87F5NC8A 4

PIN power

YES

Refer to SMPS

Troubleshooting.

MICOM PART

HECK I

Check

CN710 7PIN

P- SENS

NO

Is IC101

KIA7042

5V?

Is IC101

KIA7042

input 5V?

Check the

related part of IC101

KIA7042

AUDIO ELECTRICAL TROUBLESHOOTING GUIDE

SECTION 3. AUDIO

ELECTRICAL PART

3-2

Only for training and service purposes

LGE Internal Use Only

2. MICOM PART CHECK II

NO

YES

Refer to SMPS

Troubleshooting.

NO

Check the D101,102

1SR35 output 5V

Check IC102 KIA7031

output power

Check IC100 87F5NC8A

8 PIN power.

YES

OK

Check R1A9 680 Ω

Replace the related parts.

Check CN710

6PIN 5.6V

Check the

power of both

D102 and D101 1SR35

(Is the power of IC 100,14.40.55

89 4.8V?

YES

NO

Check IC102

KIA7031 input power.

Check the

related part.

MICOM PART CHECK II

NO

Replace the related parts.

Check the D101

1SR35 output 5V

NO

Check & replace the related

part.

Check IC 102

KIA7031 output

power

NO

Check the operation status of

R191 10K and R110 4.7K

OK OK

OK

Check

IC 102 KIA7031

input power (4.8V or input power

(4.8V or higher)

3-3

LGE Internal Use Only

3. MICOM PART CHECK III

YES

Refer to MICOM Par I,II Troubleshooting

Check the operation

status of

X101:32.768KHz and

X100:9.8304MHz

MICOM PART CHECK III

Check the IC100 14.40.56.89

input power (4.8V or higher)

OK

NO

3-4

Only for training and service purposes

LGE Internal Use Only

4. FLD DISPLAY PART CHECK

NO

YES

Refer to SMPS

Troubleshooting

NO

Replace the related part

Check CN710

assembly

Check

10 PIN → - 27V

11 PIN→ 20V 12 PIN→ 25V

YES

FLT turned on

Check the power of CN710

10 11 12 PIN

YES

Check the

connecting condition

and the power of P3702

40PIN: FL- 20

39PIN: FL+ 25

38PIN: VKK-28vor higher

39PIN: 5.6V

YES

Check

IC304 PT6324

power 50 PIN VKK:-28V

9.52 PIN +5V

YES

Check each pin

Check IC100 →

IC301 DATA communication

PIN PIN

27 PIN → 3PIN STB

26 PIN → 2PIN D

28 PIN → PIN CLK

OK

NO

Replace the related part.

NO

Replace the related part.

NO

If 5V is failed, check the input and

output power of D319 1SR35

IC100 IC303 27 PIN → 3PIN STB 28 PIN → 1PIN CLK

Check Data output

Check the data at both terminals

of LINE R330,331,332

YES

Check the related part

YES

Check the related part

OK

YES

FLD DISPLAY CHECK