LG CM4750, CMS4750F Service manual

SERVICE MANUAL

CAUTION

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

SERVICE MANUAL

Internal Use Only

Website http://biz.lgservice.com

AUGUST, 2015P/NO : AFN77277047

MODEL:

CM4750

(CM4750, CMS4750F/W)

MODEL: CM4750 (CM4750, CMS4750F/W)

Mini Hi-Fi System

CONTENTS

SECTION 1 ........ GENERAL

SECTION 2 ........ CABINET & MAIN CHASSIS

SECTION 3 ........ ELECTRICAL

SECTION 4 ........ REPLACEMENT PARTS LIST

1-1

SECTION 1

SUMMARY

CONTENTS

SERVICING PRECAUTIONS ................................................................................................................... 1-3

ESD PRECAUTIONS .................................................................................................................................. 1-5

HIDDEN KEY MODE................................................................................................................................... 1-6

SERVICE INFORMATION FOR EEPROM .......................................................................................... 1-7

PROGRAM DOWNLOAD & UPDATE GUIDE ................................................................................... 1-8

1. MCS PROGRAM ....................................................................................................................................... 1-8

2. EQ PROGRAM ......................................................................................................................................... 1-9

SPECIFICATIONS ..................................................................................................................................... 1-10

1-2

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.

Storage in conductive bag

Drop 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.

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

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 lens.

Pressure

Magnet

How to hold the pick-up

Cotton swab

Conductive Sheet

6) Never attempt to disassemble the pick-up. Spring has 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.

1-3

Pressure

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 or 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 (1 M)

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.

Armband

Resistor (1 M)

Conductive Sheet

1-4

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 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 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

HIDDEN KEY MODE

Push both Front key and RCU key to activate it for 5 seconds.

1. Disc Lock On/Off (CD Function Only Active)

 Front Key : STOP  RCU Key : STOP

2. Check Version and Option code

 Front Key : STOP  RCU Key : PLAY/PAUSE  You can change [Audio MCU Version <-> CD Controller Version <-> EEPROM Option] by SKIP+/-.

3. Clear EEPROM

 Front Key : STOP  RCU Key : SKIP-

4. Edit EEPROM

 Front Key : STOP  RCU Key : SKIP+  You can change the digit of option by SKIP+/-.  You can edit 0~f by REPEAT or PLAY/PAUSE key.

5. Bluetooth DUT

 Front Key : STOP  RCU Key : PROGRAM  Bluetooth model only

6. Power Disc Lock On/Off (CD Function Only Active)

 Front Key : STOP  RCU Key : EQ

7. Amp Clip On/Off

 Front Key : STOP  RCU Key : Mute

Amp Clip Mode Change (Amp Clip On --> Amp Clip Off --> Level Down display).

1-6

SERVICE INFORMATION FOR EEPROM

POWER ON

FLD no disc status or AUX status.

Remote control ‘Fwd skip’ + Front ‘STOP’ push same

timing during 5 seconds.

FLD ‘OP-0….

Move to appropriate position and make changes with

remote control ‘skip, mode, play’ key.

Press ENTER key

FLD ‘write ok’

Remote control ‘Fwd skip’ +

Front ‘STOP’ push same timing

FLD ‘E2P CLR’

Completed

1-7

PROGRAM DOWNLOAD & UPDATE GUIDE

1. MCS PROGRAM

Download program file name must be

- HG520_FW_CM4750_DATE.bin

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

Insert USB device at USB function.



FIRMWARE



FINISH



POWER OFF MANUALLY When completed, remove USB device.

1-8

2. EQ PROGRAM

Download program file name must be EQ_PRG_CM4750_***.BIN

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

Insert USB device at USB function.



EQ UP



FINISH



POWER OFF AUTOMATICALLY When completed, remove USB device.

1-9

SPECIFICATIONS

• GENERAL

Power requirements Refer to the main label. Power consumption Refer to the main label. Dimensions (W x H x D) 206 x 308 x 284 mm Net Weight (Approx.) 3.1 kg Operating temperature 5 °C to 35 °C (41 °F to 95 °F) Operating humidity 5 % to 90 % Bus Power Supply (USB) 5 V 500 mA

• INPUTS

AUX IN 2.0 Vrms (1 kHz, 0 dB), 75 Ω, RCA jack (L, R) x 1 PORT IN 1.2 Vrms (3.5 mm stereo jack)

• TUNER

FM Tuning Range 87.5 to 108.0 MHz or 87.50 to 108.00 MHz

• AMPLIFIER

Stereo mode 300 W + 300 W (3 Ω at 1 kHz, THD 20 %) Surround mode Front 300 W + 300 W (3 Ω at 1 kHz, THD 20 %) Subwoofer 400 W (3 Ω at 60 Hz, THD 20 %)

• CD

Frequency Response 100 to 20 000 Hz Signal-to-noise ratio 75 dB Dynamic range 75 dB

• FRONT SPEAKER

Model CMS4750F Type 2 Way 2 Speaker Impedance 4 Ω Rated Input Power 300 W Max. Input power 600 W Net Dimensions (W x H x D) 300 x 358 x 265 mm Net Weight 5.5 kg

• SUBWOOFER SPEAKER

Model CMS4750W Type 1 Way 1 Speaker Impedance 3 Ω Rated Input Power 400 W Max. Input power 800 W Net Dimensions (W x H x D) 310 x 358 x 305 mm Net Weight 5.7 kg

 Design and specifications are subject to change without notice.

1-10

SECTION 2

CABINET & MAIN CHASSIS

CONTENTS

EXPLODED VIEWS ..................................................................................................................................... 2-3

1. CABINET AND MAIN FRAME SECTION (CM4750) ................................................................................ 2-3

2. MECHANISM DECK SECTION (DP17TM3) ............................................................................................ 2-5

3. PACKING ACCESSORY SECTION ......................................................................................................... 2-7

4. SPEAKER SECTION ................................................................................................................................ 2-8

2-1

2-2

EXPLODED VIEWS

1. CABINET AND MAIN FRAME SECTION (CM4750)

FRONT

B/T

SMPS

MAIN

260L

260R

464

A47

264

463

269

262

460

464

263

255

464

A43

464

A46

464

265

266

A44

266

464

261

252

A52

259

464

A42

251

253

CABLE1

CABLE4

300

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.

2. MECHANISM DECK SECTION (DP17TM3)

1026

1439

A001

1002

1005

1001

1049

1437

1024

1030

1024

1043

1045

A005

A006

1016

1013

1015

1020

1024

1003

1439

1018

1019

1011

1012

1437

1004

3. PACKING ACCESSORY SECTION

801 Instruction Ass'y

825 FM Wire Antenna

804 Bag

808 Batter

900 Remote Contro

803 Packing

802 Bo

4. SPEAKER SECTION

4-1. FRONT SPEAKER (CMS4750F)

A60

4-2. SUBWOOFER SPEAKER (CMS4750W)

A90

2-10

SECTION 3

ELECTRICAL

CONTENTS

ONE POINT REPAIR GUIDE ................................................................................................................... 3-2

1. NO POWER ............................................................................................................................................3-2

2. NO BOOTING WHEN POWER ON THE SET........................................................................................3-4

3. VFD IS NOT DISPLAYED WHEN POWER ON THE SET .....................................................................3-5

4. NO OPERATION OF MD ........................................................................................................................3-6

5. NO SOUND ...........................................................................................................................................3-11

AUDIO ELECTRICAL TROUBLESHOOTING GUIDE ................................................................... 3-17

1. POWER (SMPS) ...................................................................................................................................3-17

2. MCS PART CHECK ..............................................................................................................................3-20

3. IC504(M24C16) CHECK .......................................................................................................................3-20

4. FLD DISPLAY CHECK .........................................................................................................................3-21

5. PWM MODULATION CHECK ...............................................................................................................3-22

6. POWER AMP PART CHECK ...............................................................................................................3-24

7. TUNER / AUX FUNCTION CHECK ......................................................................................................3-25

8. TUNER FUNCTION CHECK.................................................................................................................3-26

CDP ELECTRICAL TROUBLESHOOTING GUIDE........................................................................3-27

1. CD FUNCTION .....................................................................................................................................3-27

2. DOUBLE USB FUNCTION ...................................................................................................................3-28

WAVEFORMS OF MAJOR CHECK POINT ......................................................................................3-29

1. SDRAM .................................................................................................................................................3-29

2. SERVO ..................................................................................................................................................3-29

3. AUDIO PATH ........................................................................................................................................3-30

4. USB .......................................................................................................................................................3-31

WIRING DIAGRAM....................................................................................................................................3-33

BLOCK DIAGRAMS .................................................................................................................................3-35

1. SYSTEM BLOCK DIAGRAM ................................................................................................................3-35

2. SMPS BLOCK DIAGRAM .....................................................................................................................3-37

3. AUDIO PATH BLOCK DIAGRAM .........................................................................................................3-39

4. POWER DIAGRAM ...............................................................................................................................3-41

CIRCUIT DIAGRAMS ...............................................................................................................................3-43

1. SMPS CIRCUIT DIAGRAM ..................................................................................................................3-43

2. MAIN - DSP CIRCUIT DIAGRAM .........................................................................................................3-45

3. MAIN - SERVO CIRCUIT DIAGRAM ....................................................................................................3-47

4. MAIN - ADC/ PWM CIRCUIT DIAGRAM .............................................................................................. 3-49

5. MAIN - AMP CIRCUIT DIAGRAM.........................................................................................................3-51

6. FRONT CIRCUIT DIAGRAM ................................................................................................................3-53

CIRCUIT VOLTAGE CHART .................................................................................................................3-55

1. ICs .........................................................................................................................................................3-55

2. CAPACITORS .......................................................................................................................................3-57

PRINTED CIRCUIT BOARD DIAGRAMS .......................................................................................... 3-59

1. SMPS P.C.BOARD ...............................................................................................................................3-59

2. MAIN P.C.BOARD ................................................................................................................................3-61

3. FRONT P.C.BOARD .............................................................................................................................3-63

3-1

ONE POINT REPAIR GUIDE

1. NO POWER

If the unit doesn’t work by no power problem, repair the set according to the following guide.

1-1. FUSE & BRIDGE DIODE

1-1-1. Solution

Please check and replace F901, BD901, TH901 or TH903 on SMPS board.

1-1-2. How to troubleshoot (Countermeasure)

1) Check if the fuse F901 is open or short-circuit.

2) Check if the bridge diode BD901 is short-circuit by over current with a digital multi meter.

3) Check if the NTC thermistor TH901 or TH903 is normal or open.

1-1-3. Service hint (Any picture / Remark)

< F901 >

If F901 is not short-circuit,

replace it with a same

speciﬁ cations one.

replace it with a new one.

< BD901 >

If BD901 is short-circuit,

< TH901 >

If TH901 is open,

replace it with a new one.

3-2

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