LG LHS-75SGS, LHS-75SGC, LHS-75SGW Service Manual

- 1-1 -

[CONTENTS]

SECTION 1.GENERAL

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

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

• SPECIFICATIONS...................................................................................................................1-5

SECTION 2. ELECTRICAL

• AUDIO TROUBLESHOOTING GUIDE .................................................................................. 2-1

• DVD TROUBLESHOOTING GUIDE ...................................................................................... 2-5

• DVD DETAILS AND WAVEFORMS ON SYSTEM TESTAND DEBUGGING..................... 2-13

• WIRING DIAGRAM.............................................................................................................. 2-25

• BLOCK DIAGRAMS............................................................................................................. 2-26

• AUDIO PART SCHEMATIC DIAGRAMS ............................................................................. 2-31

• DVD PART SCHEMATIC DIAGRAMS................................................................................. 2-47

• PRINTED CIRCUIT DIAGRAMS ......................................................................................... 2-53

• CIRCUIT VOLTAGE CHART................................................................................................ 2-63

SECTION 3. EXPLODED VIEWS

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

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

• PACKING ACCESSOR Y SECTION ...................................................................................... 3-5

SECTION 4. SPEAKER PART .................................................................................. 4-1

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

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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.

Storage in conductive bag

Drop impact

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

Magnet

How to hold the pick-up

Conductive Sheet

Cotton swab

Pressure

- 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 (1M Ω)

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.

Resistor (1 Mohm)

Conductive Sheet

Resistor (1 Mohm)

Armband

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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 sur-

face 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 PERSONNELTO THE PRESENCE OF UNINSULATED “DANGEROUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAGNITUDE TO CONSTITUTE ARISK OF ELECTRIC SHOCK.

THE EXCLAMATION POINTWITHIN AN EQUILATERAL TRIANGLE IS INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANTSAFETY INFORMATION IN SERVICE LITERATURE.

- 1-5 -

SPECIFICATIONS

GENERAL

Power supply Refer to main label Power consumption Refer to main label Mass 5.5 kg External dimensions (W x H x D) 435 x 54 x 350 mm Operating conditions Temperature: 5°C to 35°C, Operation status: Horizontal Operating humidity 5% to 85%

CD/DVD

Laser Semiconductor laser, wavelength 650 nm Signal system NTSC 525/60 Frequency response (audio) 150 Hz to 18 kHz Signal-to-noise ratio (audio) More than 75 dB (1 kHz, NOP -6 dB, 20 kHz LPF/A-Filter) Dynamic range (audio) More than 70 dB Harmonic distortion (audio) 0.5 % (1 kHz, at 1W position) (20 kHz LPF)

VIDEO

Video input 1.0 V (p-p), 75 Ω, negative sync., RCA jack x 2 Video output 1.0 V (p-p), 75 Ω, negative sync., RCA jack x 1 S-video output (Y) 1.0 V (p-p), 75 Ω, negative sync., Mini DIN 4-pin x 1

COMPONENT VIDEO OUT (Y) 1.0 V (p-p), 75 ohms, negative sync, RCA jack x 1

(Pb)/(Pr) 0.7 V (p-p), 75 ohms, RCA jack x 2

TUNER

Tuning Range 87.5 - 108.0 MHz or 65.0 - 74.0 MHz, 87.5 - 108.0 MHz Intermediate Frequency 10.7 MHz Signal-to Noise Ratio 60 dB (Mono) Frequency Response 150 - 8,000 Hz

AM[MW]

Tuning Range 520 - 1,720 kHz Intermediate Frequency 450 kHz

AMPLIFIER

Stereo mode 150W + 150W (6Ω at 1 kHz, THD 10 %) Surround mode Front: 150W + 150W (THD 10 %)

Center*: 150W Surround*: 150W + 150W (6Ω at 1 kHz, THD 10 %) Subwoofer*: 250W (4Ω at 30 Hz, THD 10 %)

SPEAKERS

Front/Rear Speaker Center speaker Passive Subwoofer

(LHS-75SGS) (LHS-75SGC) (LHS-75SGW) Type 2 Way 2 Speaker 2 Way 2 Speaker 1 Way 1 Speaker Impedance 6 Ω 6 Ω 4 Ω Frequency Response 145 - 20,000 Hz 120 - 20,000 Hz 50 - 1,500 Hz Sound Pressure Level 85 dB/W (1m) 85 dB/W (1m) 83 dB/W (1m) Rated Input Power 150 W 150 W 250 W Max. Input Power 300 W 300 W 500 W Net Dimensions (W x H x D) 104 x 235 x 120 mm 220 x 115 x 120 mm 195 x 398 x 419 mm Net Weight 1.0kg 1.0kg 6.6kg

(* Depending on the sound mode

settings and the source, there may be no sound output.)

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AUDIO TROUBLESHOOTING GUIDE

1. POWER CHECK FLOW

SECTION 2. ELECTRICAL

INSERT

WER CORD.

TURN ON

THE RED LED?

YES

TURN PO

IS PO

WER ON.

WER ON?

YES

DOES INITIAL

WORK?

READ

YES

CHECK POWER PLUG

AND POWER SUPPLY CIRCUIT

CHECK POWER SUPPLY CIRCUIT.

CHECK LASER CIRCUIT

CHECK FOCUS CIRCUIT

PLAY?

DOES IT

YES

DOES IT OUTPUT

AUDIO?

YES

CHECK DISC.

CHECK TRACKING SERV

CHECK AUDIO CIRCUIT.

O CIRCUIT.

- 2-2 -

2. AUDIO µ-COM CIRCUIT

POWER ON

Does CD/DVD appear at FLD?

Does AV 1/2 FM87.5 appear at FLD?

OK.

Does READING appear at FLD?

Does no Disc or

Time appear at FLD?

Check if DVD an Audio

Micom Interface is OK.

Check power.

Check DVD Module.

Check SMPS.

Does it appear

DVD Error at

FLD?

Check

Connector(PN902)if

is normally.

Check power part

of Main B/D.

Check oscillator

of x101.

Check if IC101 PIN80 is High.

Reconnect it.

Refer to SMPS

Refer to oscillator

Circuit.

Check DVD Reset Waveform.

Check if IC101 PIN92 is High.

Check if IC101 PIN

31, 32, 51, 88 are high

(5V).

Check if IC101 PIN96 is High.

Replace IC101.

Check IC101 Reset Wavefrom.

Check 5V line.

Check Power section Circuit.

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3. FRONT CIRCUIT (1/2)

PIN104 Pins PIN : -27V PIN 6 : -18V PIN7 : -22V PIN : 5V

- 2-4 -

4. FRONT CIRCUIT (2/2)

CHECK

IF R029, R036~R040,

R046~R051

OK.

REPLACE R029, R036~R040, R046~R051

Check

if PN104 pins10, 11

Waveform OK.

Check

if the Remocon

Waveform of the

PN104 pin16

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1. POWER CHECK FLOW

DVD TROUBLESHOOTING GUIDE

READING appear at FLD?

Does

Check DVD SECTION

Check

Connector(CN201)

if is normally.

Check

Connector CN202

Check

Connector CN203

Check

voltage each pin for PN902

Check SMPS board regulator

Check Connector PN902

- 2-6 -

2. SYSTEM OPERATION FLOW

Power On

1. 8032 initializes SERVO, DSP & RISC registers

2. Write RISC code to SDRAM

3. Reset RISC

Show LOGO

YES

Tray Closed?

Tray Close to Closed position

SLED at Inner

Side ?

SLED Moves to Inner Positi on

1. Judge whether have disc and disc type

2. Jump to related disc reading procedure

Reci eve

OPEN/CLOSE

Key?

YES

1. Execute Pressed Key & IR Key

2. System operation Routine Loop

1. Stop Playback & Open Tray

2. Display tray open message & LOGO

Receive

CLOSE Key?

YES

- 2-7 -

3. TEST & DEBUG FLOW

TEST

Check the AC Voltage

Power PCBA(120V)

YES

Switch on the Power PCBA

Is the DC Voltage

outputs OK?

(5V,3.3V, 8V, 12V, -12V, 11.5V)

YES

Make sure the main PCBA don't

short on VCCs and switch it on.

Replace power PCBA or

AC transformer.

Repair or Replace P ower PCBA

Is 3.3V and 1.8V DC

outputs normal on main

PCBA?

YES

Connect to PC RS232 Cable and update the FLASH memory code.

Update FLASH

successfully?

YES

Check the regulators or related diodes.

1. Check 27MHz system clock.

2. Check system reset circuit.

3. Check FLASH R/W enable signal PRD,RWR.

4. Check RS232 SIGNALS.

5. Check FLASH Memory related circuit.

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RESET or Power On.

Show LOGO?

Flash Memory operates

properly?

YESYES

SDRAM works properly?

YES

MT1389 VIDEO outputs

properly?

YES

Have TV signal output?

YES

Check AV cable connection to TV set.

Check connection lines between FLASH & MT1389 and the FLASH access time whether is suitable or not.

Check connection lines between SDRAM & MT1389 and the SDRAM is damaged.

Check the related circuit of MT1389.

Check the filtering and amp circuit of TV signal.

Does Tray move

inside when it is not

at closed position?

YES

NO NO

Normal TROUT &

TRIN signals?

YES

Normal TRCLOSE & TROPEN signal?

YES

Normal LOAD+ &

LOADsignal?

YES

Check the cable connection between main PCBA and loader.

Check the load OPEN & CLOSE switch

Check the Tray control IO pins on MT1389 & IP4504.

Check the Tray control amplifying circuit on Motor driver.

- 2-9 -

Does

the SLED move

to inner side when it is at

outter position?

YES YES

NO NO

Motor Driver STBY

Pin is High?

Check the connection line of

STBY signal.

Do not put in disc and tray

close.

Optical Lens has

movements for searching

Focus?

Is FMSO DC Level higher

than 1.4V?

YES

SL+ and SL- output

properly?

YES

Check the cable connection with

NO NO

MECHA.

Proper FOSO outputs

to motor driver?

Check the related circuit of FMSO.

Check the amp circuit on motor driver.

Check FOSO connection on MT1389 and motor dirver.

YESYES

Proper F+ & F- outputs?

YES

Check cable connect on with

pick-up head.

Check the amp circuit on motor

dirver.

- 2-10 -

Laser turns on when reading disc?

YES

Put disc in? Laser off

YES

Disc ID is correct?

LD01 or LD02 output properly?

Collector voltage of power transistor is OK?

Check cable connection between transistor ouput and pick-up head.

Proper RFL signal on MT1389?

YES

Check the laser power circuit on MT1336 and connecting to power transistor.

Check the related circuit on laser power transistor

Check the related circuit on MT1389 RFL signal.

YES

Does spindle rotate?

YES

Check LDO1 & LDO2 signal

Proper DMSO signal on MT1389

YES

SP+ & SP- output properly?

YES

Check the cable connection between spindle and main PCBA.

Check DMSO related circuit on MT1389.

Check the spindle control amp circuit of motor driver.

- 2-11 -

YES

Focus ON OK?

YES

Track On OK?

YES

NO NO

Proper signals on

A,B,C,D of MT1389

YES

Check FEO signal

on MT1389

YES

Check FOSO signal on MT1389

Normal TEO Signal on

MT1389?

YES

Properly TRSO signal

on MT1389?

YES

Check connections between

MT1389 and pick-up head.

Check the FOSO connection on

MT1389 and motor driver.

Check the related circuit on MT1389

Check the TRSO

connection on MT1389

and motor dirver.

Disc is play ?

YES

T+ & T- output

properly?

YES

Check cable connection on

pick-up head.

Check RFO & RFLVL signal waveform.

Check the tracking control

amp circuit on motor

driver.

- 2-12 -

Normal Audio output when disc playback?

YES

Normal IR.VFD & Front pannel key functions?

YES

TEST END

NO NO

Audio PWM IC received

correct data stream?

YES

Normal Audio PWM IC

out?

YES

Check Audio filter,amplify,mute

IR.VFD Front pannelkey & MT1389

Check the cable connection on

circuit.

Communications between

is normally?

YES

Front pannel.

Check connection between MT1379

& Audio PWM IC.

Check the related

circuit of Audio PWM IC.

Check communication lines on

MT1389.

- 2-13 -

DVD DETAILS AND WAVEFORMS ON SYSTEM TEST AND DEBUGGING

1. SYSTEM 27MHz CLOCK,RESET,FLASH R/W SIGNAL

1) MT1389 main clock is at 27MHz(X601)

2) MT1389 reset is high active

FIG 1-1

FIG 1-2

- 2-14 -

3) RS232 waveform during procedure(Downloading)

4) Flash R/W enable signal during download(Downloading)

FIG 1-3

FIG 1-4

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