LG MCD112 A0U Diagram

MINI Hi-Fi SYSTEM

SERVICE MANUAL

MODEL : MCD112 (MCS112F)

CAUTION

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

.

Website http://biz.lgservice.com

MODEL : MCD112 (MCS112F)

SERVICE MANUAL

P/NO : AFN72956656 APRIL, 2009

Internal Use Only

CONTENTS

SECTION 1 GENERAL

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

• NOTES REGARDING HANDLING OF THE PICK-UP

• NOTES REGARDING COMPACT DISC PLAYER REPAIRS

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

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

SPECIFICATIONS .................................................1-7

SECTION 2 EXPLODED VIEWS

CABINET EXPLODED VIEW................................2-1

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

1. TAPE DECK MECHANISM

(A/S & A/S : RIGHT A/S DECK) ..................2-3

2. TAPE DECK MECHANISM

(A/S & A/S : LEFT A/S DECK) ....................2-5

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

3. PS9829B ....................................................3-15

4. PT6324 .......................................................3-15

5. STR-S6757IF1905......................................3-16

6. TAS5142 .....................................................3-17

7. U1739EJ2V1UD00/KF2_E .........................3-18

WIRING DIAGRAM .............................................3-19

BLOCK DIAGRAMS ...........................................3-21

1. SMPS BLOCK DIAGRAM .........................3-21

2. MAIN & FRONT BLOCK DIAGRAM .........3-23

SCHEMATIC DIAGRAMS ...................................3-25

1. SMPS SCHEMATIC DIAGRAM ................3-25

2. MAIN SCHEMATIC DIAGRAM..................3-27

3. AMP SCHEMATIC DIAGRAM ...................3-29

4. DECK SCHEMATIC DIAGRAM.................3-31

5.

FRONT SCHEMATIC DIAGRAM

6.

KEY-L SCHEMATIC DIAGRAM

7.

KEY-R SCHEMATIC DIAGRAM

PRINTED CIRCUIT BOARD DIAGRAMS...........3-37

1. MAIN P.C.BOARD .....................................3-37

2. FRONT P.C.BOARD ..................................3-41

3. SMPS P.C.BOARD ....................................3-43

4. KEY-L P.C.BOARD ....................................3-44

5. KEY-R P.C.BOARD ...................................3-44

.................3-33

...................3-35

...................3-36

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

MODEL : MCS112F.........................................2-9

PACKING ACCESSORY VIEW...........................2-13

SECTION 3 AUDIO PART ELECTRICAL

AUDIO ELECTRICAL

TROUBLESHOOTING GUIDE..............................3-1

1. POWER (SMPS) .........................................3-1

2. P-SENS .......................................................3-2

3. VKK CHECK................................................3-2

4. MICOM PART CHECK I ..............................3-2

5. MICOM PART CHECK II .............................3-3

6. IC103(KS4CD21CS) CHECK......................3-4

7. FLD DISPLAY CHECK ................................3-5

8. PWM MODULATION PART CHECK ...........3-6

9. POWER AMP PART CHECK ......................3-7

10. AUX FUNCTION CHECK ............................3-8

11. TUNER FUNCTION CHECK .......................3-9

12. TAPE FUNCTION CHECK ........................3-10

13. TAPE PLAY PART CHECK ........................3-11

14. TAPE REC PART CHECK .........................3-12

INTERNAL BLOCK DIAGRAM OF ICs..............3-13

1. ES6838.......................................................3-13

2. HA12237F. ..................................................3-14

SECTION 4 CD PART ELECTRICAL

CD ELECTRICAL

TROUBLESHOOTING GUIDE..............................4-1

1. CD PART TROUBLESHOOTING................4-1

2. USB PART TROUBLESHOOTING..............4-9

WAVEFORMS OF MAJOR CHECK POINT .......4-10

SCHEMATIC DIAGRAMS ...................................4-13

1. CD SCHEMATIC DIAGRAM .....................4-13

2. USB SCHEMATIC DIAGRAM ...................4-15

PRINTED CIRCUIT BOARD DIAGRAM.............4-17

CD P.C.BOARD .............................................4-17

SECTION 5 REPLACEMENT PARTS LIST

............................................5-1

1-1

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.

LGE Internal Use Only

1-2

Only for training and service purposes

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.

1-3

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 know 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]

THE LIGHTNING FLASH WITH ARROWHEAD 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 INTENED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE LITERATURE.

LGE Internal Use Only

1-4

Only for training and service purposes

LOCATION OF USERS CONTROLS

FRONT PANEL

1

2

6

7

3

4

5

1. POWER

You can set up the unit into an economic power save mode. In the power-on status, press and hold

(POWER) for about 3 seconds. To cancel

power save mode, press (POWER).

2. ST./MONO

Press ST./MONO. This will change the tuner from stereo to mono and usually improve the reception.

3. MP3 OPT. (MP3 Optimizer)

This function is optimized for compressible MP3 files so that it improves the bass sound.

4. DEMO

Press DEMO in power off state to demonstrate the function on display window. To cancel it, press or DEMO again.

5. Headphone jack

Connect a headphone plug (ø3.5 mm) into the jack to listen to the sound through headphones (not supplied).

8

9

10

11

6. CD tray

7. XTS - PRO

The function creates the optimum sound for you to play of the original sound. Each time you press XTS - PRO, “XTS -- PRO ON” or “XTS -- PRO OFF” is displayed in turn. (The XTS Pro function will not be operated when a headphone has been connected.)

8. D.SKIP

If more than one portable USB player is connected to the system at the same time, press D.SKIP to select one of them.

9. AUX

You can connect many other types of audio or audio visual device to the system via the auxiliary sockets (AUX IN) on the back of the player.

10.VOLUME

Control the volume when using any function.

11. USB connector - OPTIONAL

Connect a remote USB compatible player here.

1-5

LGE Internal Use Only

REMOTE CONTROL

1

2

3

4

5

6

7

8

9

10

11

12

13

14

1. Search for a folder of MP3/WMA files

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

2. Fall asleep while listening to your player

Firstly, start a radio station or music. Press SLEEP on the remote one or more times to select a delay of between 10 and 180 minutes, after which the player will turn off.

3. Use when playing a CD

4. Listen to your tracks again and again

Press REPEAT once to repeat the track currently playing. Press REPEAT twice to repeat the whole CD, or if you’re listening to the whole folder of MP3/WMA CD . The display will show what is being repeated.

5. Use when playing a cassette tape

6. Sound quality adjustment

You can select a desired sound mode by using EQ.

7. Play any track on a CD

Press the corresponding number buttons on the remote control.

8. Temporarily stop the sound

Press the button again to return to the sound.

9. To change the functions

Change the functions between FM, AM, CD, AUX, USB or TAPE

10.Dimm the display light

11. For storing radio stations

If you have saved radio stations using PROGRAM/ MEMO, you can scroll through them and select one (see Listening to the radio).

12.eXtreme Dynamic Sound System

Reinforce the treble, bass and surround sound effect. XDSS ON will show in the display. Press again for XDSS OFF.

13.RANDOM

Press RANDOM, play tracks/files you can in a random order or cancel it.

14.See information about your music

MP3/WMA files often come with tags. The tag gives the Title, Artist or Album. Press INFO while a file is playing to see this information. If there are no tags, “NO ID3 TAG” or “NO WMA TAG” will show.

LGE Internal Use Only

1-6

Only for training and service purposes

SPECIFICATIONS

• GENERAL

Net Weight 5.57kg (MCD212 Model)

5.36kg (MCD112 Model)

External dimensions (WxHxD) 170 x 243 x 282mm

• TUNER

FM Tuning Range 87.5 ~ 108.0MHz or 65 ~ 74MHz,

87.5 ~ 108.0MHz

AM Tuning Range 522 ~ 1620kHz or 520 ~ 1720kHz

• AMPLIFIER

Output Power 100W + 100W (MCD212 Model)

50W + 50W (MCD112 Model) T.H.D 0.5% Frequency Response 40 ~ 20000Hz Signal-to-noise ratio 75dB

• CD

Frequency response 40 ~ 20000Hz Signal-to-noise ratio 75dB Dynamic range 75dB

• SPEAKERS

MCS212F Type Bass Reflex 2 Way 2 Speaker

Impedance 4Ω Rated Input Power 100W Max. Input Power 200W Net Dimensions (WxHxD) 220 x 342 x 270mm Net Weight (1EA) 3.46kg

MCS112F Type Bass Reflex 2 Way 2 Speaker

Impedance 4Ω Rated Input Power 50W Max. Input Power 100W Net Dimensions (WxHxD) 200 x 337 x 228mm Net Weight (1EA) 2.92kg

1-7

LGE Internal Use Only

MEMO

LGE Internal Use Only

1-8

Only for training and service purposes

SECTION 2 EXPLODED VIEWS

255

256

E

F

G

I

J

H

A

B

M

N

A

J

K

H

L

K

M

I

C

G

E

F

D

A26

A41

A47

A46

266

263

305

451

267

289

456

450

264

458

450

290

454

CABLE2

CABLE4

CN806

P9701

P9702

260

CD

MAIN

SMPS

291

257

255

259

253

254

450

N

C

450

A00

CABLE1

CABLE5

CN201

CABLE3

A43

A40

FRONT

CABINET EXPLODED VIEW

2-1 2-2

LGE Internal Use Only

TAPE DECK MECHANISM EXPLODED VIEW

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

BRASS MOTOR PULLEY MAYBE CHANGED FOR WOW FLUTTER WHEN NECESSARY

009

003

A00

001

002

007

008

022

006

016

015

017

023

018

019

025

020

A01

RING FW MAYBE ADDED FOR WOW FLUTTER WHEN NECESSARY

011

LGE Internal Use Only

009

013

A02

2-3 2-4

Only for training and service purposes

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

019

A00

003

009

007

008

016

017

022

018

023

015

020

RING FW MAYBE ADDED FOR WOW FLUTTER WHEN NECESSARY

024

011

009

013

A03

2-5 2-6

LGE Internal Use Only

CD MECHANISM EXPLODED VIEW

416

151

159

165

164

417

166

417

167

416

177

175

172

170

419

417

418

190

189

188

A30

A32

A26

181

187

186

184

421

185

156

155

153

173

168

163

162

441

440

422

A35

417

LGE Internal Use Only

2-7 2-8

Only for training and service purposes

SPEAKER EXPLODED VIEW

MODEL : MCS112F

A80L

A80R

A80AL

A80AR

850L

850R

853

A80B

855

856

854

851

852

WIRE80

2-9 2-10

LGE Internal Use Only

MEMOMEMO

LGE Internal Use Only

2-11 2-12

Only for training and service purposes

PACKING ACCESSORY VIEW

2-13

LGE Internal Use Only

MEMO

LGE Internal Use Only

2-14

Only for training and service purposes

SECTION 3 AUDIO PART ELECTRICAL

AUDIO ELECTRICAL TROUBLESHOOTING GUIDE

1. POWER (SMPS)

POWER (SMPS)

YES

Check the fuse

F901

YES

Check

the DC V of C905.

If DC V is over

400V

YES

Chcek the

DC V of C909, C903,

C921 If DC V is in 14~19V

and it is steady.

YES

Check the

DC V of C981, C945.

If DC V is 6.1V

NO

Replace the fuse

Check BD901, LF901, 902

Check IC901, 902

YES

Check short of

P9701, P9702 line

Check short of P9702 line

NONO

Replace IC 901,902

YES

Chcek the

DC V of C950, C951

If DC V is in

31.5V

YES

OK

NO

Check short of P9701 line

3-1

LGE Internal Use Only

2. P-SENS

P-SENS

YES

Check

the PIN6 of P9702

If DC V is over 5.6V

3. VKK CHECK

VKK check

Check

the PIN3 of P9702

If DC V is over -28V ±2

OK

YES

NO

Check power circuit Trouble shooting

4. MICOM PART CHECK I

MICOM part check I

YES

Check P-SENS

(P7904)_PIN6.

YES

Check both

end voltage of IC101

(KIA7042).

YES

Check voltage of IC100

78KO/KF2_PIN1.

YES

OK OK

LGE Internal Use Only

NO

SMPS troubleshooting.

NO

Check if IC101(KIA7042) of output voltage is over 4.3V.

Refer to

Check

if input voltage of

IC101(KIA7042) is

over 5V.

YES

NO

3-2

Check the

periphery of IC101

(KIA7042).

YES

Only for training and service purposes

NO

Replace IC101

(KIA7042).

5. MICOM PART CHECK II

MICOM part check II

YES

voltage of P7904_PIN5

Check if

is 5.6V.

YES

Check

both end voltage of

D101

YES

Check

Q101_ emitter/collector

5V.

YES

NO

NO NO

Refer to

SMPS troubleshooting.

Check if output of

D101(1SR35) is 5V.

YES

Check D101.

YES

OK

Check Q102_base

0.6V HIGH.

YES

NO

Replace D101.

Check if output of IC101

(KIA7042) is over 4.3V.

YES

Check if IC103_PIN8 and

IC100_PIN19, 20, 59 are 5V.

YES

X101 : 32.768kHz

X100 : 9.8304MHz

Check the operation.

YES

OK

Q102_collector 0.6V LOW.

Check Q102.

OK

YES

3-3

NO

Check IC101.

YES

OK

Replace Q102.

NO

Replace IC101.

LGE Internal Use Only