LG OM7550 Service Manual

SERVICE MANUAL

Internal Use Only

Website http://biz.lgservice.com

AUGUST, 2015P/NO : AFN77277050

MODEL: OM7550

Mini Hi-Fi Audio

SERVICE MANUAL

MODEL: OM7550

CAUTION

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

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. AUDIO PROGRAM ................................................................................................................................... 1-8

2. CD PROGRAM ......................................................................................................................................... 1-9

3. EQ PROGRAM ....................................................................................................................................... 1-10

SPECIFICATIONS ........................................................................................................................................... 1-11

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

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 & UPDATE GUIDE

1. AUDIO PROGRAM

Download program file name must be MICOM_OM9550_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

1) (Fast) Format USB device

2) Copy Firmware file to USB device.

NO USB

Insert USB device at USB function



MICOM UP



FINISH



Auto POWER OFF

1-8

2. CD PROGRAM

Download program file name must be HG590_OM9550_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

1) (Fast) Format USB device

2) Copy Firmware file to USB device.

NO USB

Insert USB device at USB function



FIRMWARE



FINISH



Auto POWER OFF

1-9

3. EQ PROGRAM

Download program file name must be EQ_PRG_OMXX50_YYMMDDX_XXXX.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

1) (Fast) Format USB device

2) Copy Firmware file to USB device.

NO USB

Insert USB device at USB function



EQ UP



FINISH



Auto POWER OFF

1-10

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) 430 mm x 765 mm x 468 mm Net Weight (Approx.) 22.7 kg Operating temperature 5 °C to 35 °C (41 °F to 95 °F) Operating humidity 60 % Bus Power Supply 5 V 500 mA

• INPUTS / OUTPUTS

AUX IN / OUT 2,0 Vrms (1 kHz, 0 dB), 600 Ω, RCA jack (L, R) PORT. IN 1,2 Vrms (3.5 Ø jack) MIC 20 mV

• TUNER

FM Tuning Range 87,5 to 108,0 MHz or 87,50 to 108,00 MHz

• CD

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

• AMPLIFIER

Total output 1000 W FRONT 500 W x 1 (6 Ω at 150 Hz) Subwoofer 500 W x 1 (6 Ω at 1 kHz) THD 20 %

• Design and specifications are subject to change without notice.

1-11

1-12

SECTION 2

CABINET & MAIN CHASSIS

CONTENTS

DISASSEMBLY INSTRUCTIONS ..................................................................................................................... 2-2

1. HOW TO DISASSEMBLE THE SIDE COVER (LEFT & RIGHT) ............................................................. 2-2

EXPLODED VIEWS ........................................................................................................................................... 2-5

1. CABINET AND MAIN FRAME SECTION ................................................................................................. 2-5

2. DECK MECHANISM SECTION (DM19) ................................................................................................... 2-7

3. PACKING ACCESSORY SECTION ......................................................................................................... 2-9

2-1

DISASSEMBLY INSTRUCTIONS

1. HOW TO DISASSEMBLE THE SIDE COVER (LEFT & RIGHT)

Step 1) Insert JIG into groove and then raise Cover_Side with a lever(JIG) to outside direction.

-,*

Figure 1

Step 2) Tap(Push-silde) Cover_Side to back direction.

Figure 2

2-2

Step 3) Seperate Cover_Side to out direction.

Figure 3

2-3

2-4

2-62-5

EXPLODED VIEWS

1. CABINET AND MAIN FRAME SECTION

MAIN

SMPS

TOP

VFD

FRONT

B/T

468

A52

255

256

257

468

263

264

265

266

267

268

270

A46

468

443

285

286

284

283

282

A47

443

260

262

261

A41

250

251

443

A44

254

A43

A42

443

A49

A50

275

277

276

279

512

278

252

468

512

443

518

CABLE2

CABLE3

281

512

CABLE5

1439

A001

1002

1043

A005

1016

1013

1015

1020

1439

1018

1019

1012

A006

1045

1026

1049

1437

1024

1437

1005

1001

1003

1004

1011

1030

2. DECK MECHANISM SECTION (DM19)

2-82-7

3. PACKING ACCESSORY SECTION

825 FM Antenna

300 Power Cord

Owner’s manual

801A

Owner’s manual

801B

801C

Owner’s manual

900 Remote Control

803 Packing

804 Bag

803 Packing

808 Batteries

803 Packing

2-9

802 Box

2-10

SECTION 3 ELECTRICAL

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

CONTENTS

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. NO POWER ON (STANDBY LED IS BLINKING) ......................................................................................................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. POWER BLOCK DIAGRAM ..................................................................................................................................... 3-45

CIRCUIT DIAGRAMS .......................................................................................................................................................... 3-47

1. SMPS_POWER #1 CIRCUIT DIAGRAM ................................................................................................................. 3-47

2. SMPS_POWER #2 CIRCUIT DIAGRAM ................................................................................................................. 3-49

3. MAIN_CD DSP CIRCUIT DIAGRAM ....................................................................................................................... 3-51

4. MAIN_ADC/PWM CIRCUIT DIAGRAM.................................................................................................................... 3-53

5. MAIN_RF SERVO CIRCUIT DIAGRAM .................................................................................................................. 3-55

6. MAIN_AMP CIRCUIT DIAGRAM ............................................................................................................................. 3-57

7. MAIN_AUX OUT/ VFD PWR CIRCUIT DIAGRAM .................................................................................................. 3-59

8. FRONT CIRCUIT DIAGRAM.................................................................................................................................... 3-61

9. VFD/RMC1 CIRCUIT DIAGRAM.............................................................................................................................. 3-63

10. TOP CIRCUIT DIAGRAM ......................................................................................................................................... 3-65

CIRCUIT VOLTAGE CHART ............................................................................................................................................... 3-67

1. ICs ............................................................................................................................................................................ 3-67

2. CAPACITORS .......................................................................................................................................................... 3-68

3. CONNECTORS ........................................................................................................................................................ 3-69

4. ZENER DIODES ...................................................................................................................................................... 3-70

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

1. SMPS P. C. BOARD (TOP VIEW) ........................................................................................................................... 3-71

2. SMPS P. C. BOARD (BOTTOM VIEW) ................................................................................................................... 3-73

3. MAIN, VFD/RMC1 P.C.BOARD (TOP VIEW) .......................................................................................................... 3-75

4. MAIN, VFD/RMC1 P.C.BOARD (BOTTOM VIEW) .................................................................................................. 3-77

5. FRONT P.C.BOARD (TOP VIEW) ........................................................................................................................... 3-79

6. FRONT P.C.BOARD (BOTTOM VIEW) ................................................................................................................... 3-79

7. TOP(VOLUME_FR1) P.C.BOARD (TOP VIEW) ...................................................................................................... 3-81

8. TOP(VOLUME_FR1) P.C.BOARD (BOTTOM VIEW) .............................................................................................. 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/ THERMISTOR

1-1-1. Solution

Please check and replace F901, BD901, TH900, TH901 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 multimeter.

3) Check if the NTC thermistor TH900~TH902 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.

If BD901 is short-circuit,

replace it with a new one.

< BD901 >

3-2

< TH900, TH901 > If TH900~TH901 is open, replace it with a new one.

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, Q905~Q906 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 Q905~Q906 with a digital multimeter.  If it is short condition, it’s destroyed. Replace it with a new one. (Please replace 2 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.

< Q905~Q906 >

If Q905~Q906 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 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

+ 58 hidden pages

LG OM7550 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual