LG CM9750 Schematic

SERVICE MANUAL

CAUTION

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

Internal Use Only

Website http://biz.lgservice.com

JULY, 2015

MODEL: CM9750 (CM9750, CMS9750F)

MODEL: CM9750

(CM9750, CMS9750F)

MINI HI-FI SYSTEM

P/NO : AFN77277023

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 GUIDE ...................................................................................................................... 1-8

FOTA UPDATE ................................................................................................................................................ 1-11

SPECIFICATIONS ........................................................................................................................................... 1-12

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

HIDDEN MODE KEYS

Version Check Front Stop + RMC ‘ ’ for 5s

EEPROM Initial Front Stop + RMC ‘ ’ for 5s

EEPROM Edit Front Stop + RMC ‘ ’ for 5s

APD Test Display Front Stop + RMC ‘3’ for 5s

Clip Front Stop + RMC ‘Mute’ for 5s

Disc Lock On/Off Front Stop + RMC ‘Stop’ for 5s

Front Stop + RMC ‘EQ’ for 5s

Power Disc Lock On/Off

Demo All Key Lock On/Off Front Stop + RMC ‘9’ for 5s

BT Auto Power On/Off Front/RMC Power Key for 5s

Child Safe On/Off Volume 0(Min) + Front ENTER Key for 3s

or Front Stop + Front Open for 5s

1-6

SERVICE INFORMATION FOR EEPROM

POWER ON

VFD “NO DISC” status

Front ‘STOP’ + Remote control “ ”

push same timing during 5s

FLD “OP00-…..”

Move to appropriate position

And make changes

with RMC “ , , , REPEAT” key.

It is possible at any function. (ex. It is possible at VFD “NO USB” status, too.) This is an example.

Press STOP Key

VFD “WRITE OK”

Front ‘STOP’ + Remote control “ ”

push same timing during 5s

VFD “E2P CLR”

Completed

1-7

PROGRAM DOWNLOAD GUIDE

1. AUDIO PROGRAM

Download program file name must be MICOM_CM8450_YYMMDDX.HEX

If security program(Water Wall) is activated on PC, you must save the file to the USB storage device and disable the security software, then download the file to your set. Downloading file proceeds in the same way at USB1 function and USB2 function.

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



MICOM UP



FINISH



Auto POWER OFF

1) (Fast) Format USB device

2) Copy Firmware file to USB device.

1-8

2. CD PROGRAM

Download program file name must be HG580_CM8450_YYMMDDX.bin

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



Auto POWER OFF

1) (Fast) Format USB device

2) Copy Firmware file to USB device.

1-9

3. EQ PROGRAM

Download program file name must be EQ_PRG.BIN

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



Auto POWER OFF

1) (Fast) Format USB device

2) Copy Firmware file to USB device.

1-10

FOTA UPDATE

Step1 : App connecting

(Check FW version)

Step4 : Download from CDN server

Step2 : Device version info

Step5 : Transfer FW

Step3 : Select update button

Step6 : FW Flash Writing

Step7 : FOTA complete

1-11

SPECIFICATIONS

• GENERAL

Power requirements Refer to the main label. Power consumption Refer to the main label. Networked standby : 0.4 W (If all network ports are activated.) Dimensions (W x H x D) 450 mm x 160 mm x 335 mm Net Weight (Approx.) 6.5 kg Operating temperature 5 °C to 35 °C (41 °F to 95 °F) Operating humidity 60 % Bus Power Supply 5 V 500 mA

• INPUTS

AUX IN 2.0 Vrms (1 kHz, 0 dB), 600 Ω, RCA jack (L, R) PORT. IN 1.2 Vrms (3.5 Ø jack) MIC 27 mV

• CD

Frequency Response 40 to 20 000 Hz Signal-to-noise ratio 75 dB Dynamic range 80 dB

• AMPLIFIER

Total output 3 000 W FRONT 500 W x 2 (4 Ω at 1 kHz) WOOFER 1 000 W x 2 (8 Ω at 70 Hz) THD 25 %

• FRONT SPEAKER

Type Front : 2 Way 2 Speaker Surround : 1 Way 1 Speaker Impedance Front : 4 Ω Surround : 8 Ω Rated Input Power Front : 500 W Surround : 1 000 W Max. Input power Front : 1 000 W Surround : 2 000 W Net Dimensions (W x H x D) 414 mm x 562 mm x 376 mm Net Weight 18.3 kg

• Design and specifications are subject to change without notice.

1-12

SECTION 2

CABINET & MAIN CHASSIS

CONTENTS

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

1. CABINET AND MAIN FRAME SECTION ................................................................................................. 2-3

2. MECHANISM DECK SECTION ................................................................................................................ 2-5

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

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

2-1

2-2

MAIN

A46

443

273

468

A47

443

274

266

443

467

509

468

262

FRONT

FRONT_CTRL

NFC Tag

443

253

CABLE1

A52

443

A45

443

263

265

443

CABLE2

272

252

A42

250

251

254

SMPS

276

275

468

467

263

467

264

443

498

271

498

271

467

270

A43

300

EXPLODED VIEWS

1. CABINET AND MAIN FRAME SECTION

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.

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

2. MECHANISM DECK SECTION

3. PACKING ACCESSORY SECTION

801 Owner’s manual

Filter, Ferrite Core

826A

803 Packing

804 Bag

808 Batteries

900 Remote Control

Packing803

802 Box

4. SPEAKER SECTION

A60L

A60R

SECTION 3 ELECTRICAL

CONTENTS

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

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

2. NO AMP POWER ................................................................................................................................... 3-3

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

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

5. AUDIO OUTPUT IS SMALL OR NO AUDIO OUTPUT .......................................................................... 3-6

6. D-PROTECTION IS DISPLAYED ........................................................................................................... 3-7

7. SPEAKER NO AUDIO ............................................................................................................................ 3-8

8. NO BOOTING IN CD/USB FUNCTION .................................................................................................. 3-9

9. NO OPERATION OF MD ...................................................................................................................... 3-14

10. NO SOUND ........................................................................................................................................... 3-19

ELECTRICAL TROUBLESHOOTING GUIDE ................................................................................................. 3-25

1. POWER SUPPLY ON SMPS BOARD .................................................................................................. 3-25

2. SYSTEM PART ..................................................................................................................................... 3-28

3. NO AUDIO CHECK ............................................................................................................................... 3-29

4. NO LIGHTING (SPEAKER LED) .......................................................................................................... 3-34

WAVEFORMS OF MAJOR CHECK POINT .................................................................................................... 3-35

1. DSP (IC501) .......................................................................................................................................... 3-35

2. PWM (IC202) ........................................................................................................................................ 3-36

3. SERVO (IC401) ..................................................................................................................................... 3-37

4. MOTOR DRIVER (IC400) ..................................................................................................................... 3-38

5. ADC (IC201) .......................................................................................................................................... 3-39

6. USB (CN502) ........................................................................................................................................ 3-39

7. BLUETOOTH (CN504) .......................................................................................................................... 3-40

WIRING DIAGRAM .......................................................................................................................................... 3-41

BLOCK DIAGRAMS ........................................................................................................................................ 3-43

1. SYSTEM BLOCK DIAGRAM ................................................................................................................ 3-43

2. SMPS BLOCK DIAGRAM ..................................................................................................................... 3-45

3. POWER BLOCK DIAGRAM ................................................................................................................. 3-47

CIRCUIT DIAGRAMS ...................................................................................................................................... 3-49

1. SMPS - POWER #1 CIRCUIT DIAGRAM ............................................................................................ 3-49

2. SMPS - POWER #2 CIRCUIT DIAGRAM ............................................................................................ 3-51

3. MAIN - CD DSP CIRCUIT DIAGRAM ................................................................................................... 3-53

4. MAIN - ADC/ PWM CIRCUIT DIAGRAM .............................................................................................. 3-55

5. MAIN - RF SERVO CIRCUIT DIAGRAM .............................................................................................. 3-57

6. MAIN - EXP/ VISENSE CIRCUIT DIAGRAM ....................................................................................... 3-59

7. MAIN - AMP CIRCUIT DIAGRAM......................................................................................................... 3-61

8. MAIN - MIC/ AUX CIRCUIT DIAGRAM ................................................................................................ 3-63

9. FRONT CIRCUIT DIAGRAM ................................................................................................................ 3-65

10. FRONT_CTRL CIRCUIT DIAGRAM ..................................................................................................... 3-67

CIRCUIT VOLTAGE CHART ........................................................................................................................... 3-69

1. CAPACITORS ....................................................................................................................................... 3-69

2. CONNECTORS ..................................................................................................................................... 3-70

PRINTED CIRCUIT BOARD DIAGRAMS ....................................................................................................... 3-71

1. SMPS P.C.BOARD ............................................................................................................................... 3-71

2. MAIN P.C.BOARD ................................................................................................................................ 3-75

3. FRONT P.C.BOARD ............................................................................................................................. 3-79

4. FRONT_CTRL P.C.BOARD .................................................................................................................. 3-83

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/ FET

1-1-1. Solution

Please check and replace F901, BD901, BD902, Q902~Q905 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 or BD902 is short-circuit by over current with a digital multimeter.

3) Check if the FET Q902 ~ Q905 is normal or short.  If it is short condition, it’s destroyed. Replace it with a new one. (Please replace 4 FET at the same time although several FET is OK)

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

< F901 >

If F901 is not short-circuit,

replace it with a same

speciﬁ cations one.

If BD901, BD902 is short-circuit,

<BD901, BD902 >

replace it with a new one.

< Q902 ~ Q905 >

If Q902 ~Q905 is short (pin1-3),

replace it with a new one.

3-2

ONE POINT REPAIR GUIDE

2. NO AMP POWER

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

2-1. FUSE/ FET

2-1-1. Solution

Please check and replace F911, Q911 ~ Q914 on SMPS board.

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

1) Check if the fuse F911 is open or short-circuit.

2) Check the Drain-Source or Drain-Gate, Gate-Source Resistance of Q911~Q914 with a digital multimeter.  If it is short condition, it’s destroyed. Replace it with a new one. (Please replace 4 FET at the same time although several FET is OK)

2-1-3. Service hint (Any picture / Remark)

< F911 >

If F911 is not short-circuit,

replace it with a same speciﬁ cations one.

< Q911 ~ Q914 >

If Q911 ~ Q914 is short-circuit,

replace it with a new one.

3-3

ONE POINT REPAIR GUIDE

X500

(24 MHz)

X501

(32.768 kHz)

KEY2

(R526)

R522

PWR_CTRL

3. NO BOOTING WHEN POWER ON THE SET

The set doesn’t work when press the power button on the FRONT_CTRL board or the remote control.

3-1. IC501

3-1-1. Solution

Replace IC501 on MAIN board.

3-1-2. How to troubleshoot (Countermeasure)

1) Check the 5.6 VA (CN106) and DVCC_3.3 V (IC505) in standby mode.  If there is no 5.6 VA, check the SMPS and if doesn’t appear 3.3 V, check IC505.

2) Check 5.6 VA, +12 V, FL+, FL-, an +39 V when power on the set.  If the set doesn’t work regardless of what the KEY2 changes high to low while pressing the power button. X500 and X501 work normally but, if you can not power on the set, replace the IC501 with a new one on the MAIN board.

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

X501

(32.768 kHz)

KEY2

(R526)

< MAIN board top view >

R522

PWR_CTRL

X500

(24 MHz)

< MAIN board bottom view >

3-4

ONE POINT REPAIR GUIDE

CN315

VFD_STB,

VFD_CLK,

VFD_DO

4. VFD IS NOT DISPLAYED WHEN POWER ON THE SET

When power on the set, any icons or characters on VFD are not displayed.

4-1. VFD (VFD301)

4-1-1. Solution

Please check and replace VFD301 on FRONT board.

4-1-2. How to troubleshoot (Countermeasure)

1) Check if 39 V, FL+ and FL- are output from SMPS to VFD via the MAIN board.

2) Check if the IC501 outputs VFD_RST, VFD_CLK, VFD_DO, and VFD_STB to the FRONT board.

3) Check if the VFD grid current amplifier circuit on the FRONT board. Check the drive signal to the transistor’s base.  If the control signals from VFD (DGND_2, VH, VDD) isn’t output, replace VFD with a new one.

4-1-3. Service hint (Any picture / Remark)

CN315

VFD_STB,

VFD_CLK,

VFD_DO

R327(TP 304) Q301 Emitter

< FRONT circuit > < Waveform of the grid current driver>

about

30 Vp-p

3-5

ONE POINT REPAIR GUIDE

IC700~IC705

5. AUDIO OUTPUT IS SMALL OR NO AUDIO OUTPUT

Audio signal output is small or not. when you power on the Middle Power Mini System.

5-1. AMP IC (IC700~IC705)

5-1-1. Solution

Replace IC700~IC705 on MAIN board.

5-1-2. How to troubleshoot (Countermeasure)

1) Please check if this system is on bass blast mode.  C, RL and RR make sound only on bass blast mode.

2) Check the IC700~IC705 on your eyes.

3) Check the audio signal output check (pin13 of IC700~IC705). First, Check the PWM Data input (pin3 of IC700~IC705)

4) If the audio signal output has no output, try to change IC which has no output.

5) Lastly, check Speaker Terminal (TM700).

5-1-3. Service hint (Any picture / Remark)

IC700~IC705

< MAIN board top view >

3-6

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