LG LX-220 Service manual

SECTION 1. GENERAL

SERVICING PRECAUTIONS

[CONTENTS]

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1-2

ESD PRECAUTIONS

SPECIFICATION

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1-4

1-5

SECTION 2. TROUBLESHOOTING

ADJUSTMENTS

TROUBLESHOOTING...............................................................................................................2-3

WAVEFORMS OF MAJOR CHECK POINT...............................................................................2-7

BLOCK DIAGRAM

SCHEMATIC DIAGRAMS

WIREING DIAGRAM................................................................................................................2-26

PRINTED CIRCUIT DIAGRAMS..............................................................................................2-28

INTERNAL BLOCK DIAGRAM OF ICs....................................................................................2-39

PRINTED CIRCUIT DIAGRAMS

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2-1

2-16

2-18

2-53

SECTION 3. EXPLODED VIEWS

CABINET AND MAIN FRAME SECTION

...................................................................................

3-1

SECTION 4. SPEAKER SECTION

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

SECTION 5. REPLACEMENT PARTS LIST

REPLACEMENT PARTS LIST

....................................................................................................

- 1-1-

5-1

SECTION 1. GENERAL

SERVICING PRECAUTIONS

[NOTES REGARDING HANDLING OF THE PICK-UP]

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

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!

NEVER look directly at the laser beam, and don!t let contact fingers or other exposed skin.

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

Magnet

How to hold the pick-up

Cotton swab

Conductive Sheet

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

- 1-2-

Pressure

[NOTES REGARDING COMPACT DISC PLAYER REPAIRS]

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.

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 )

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

Resistor (1 Mohm)

Conductive Sheet

(1 Mohm)

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.

VOLUME

VOLUME KNOB

DOWN

RESET jump wire

- 1-3-

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.

- 1-4-

Dual-trace

Electronic

SECTION 2. ELECTRICAL SECTION

ADJUSTMENTS

This set has been aligned at the factory and normally will not require further adjustment. As a result, it is not recommended that any attempt is made to modificate any circuit. If any parts are replaced or if anyone tampers with the adjustment, realignment may be necessary.

IMPORTANT

1. Check Power-source voltage.

2. Set the function switch to band being aligned.

3. Turn volume control to minimum unless otherwise noted.

4. Connect low side of signal source and output indicator to chassis ground unless otherwise specified.

5. Keep the signal input as low as possible to avoid AGC and AC action.

TAPE DECK ADJUSTMENT

1. AZIMUTH ADJUSTMENT

Deck ModeTest TapeTest TapeAdjustmentAdjust for

PalybackMTT-114Speaker Out

DECK Screw

Azimuth Screw

Maximum

synchroscope

CH1 CH2

GND

Test Tape MTT-114

Voltmeter

Head

L ch

R ch

Playback Mode

Unit

Figure 1. Azimuth Adjustment Connection Diagram

Speaker Out

L out

R out

2. MOTOR SPEED ADJUSTMENT

Deck ModeTest TapeTest TapeAdjustmentAdjust for

Rec/PauseMTT-5511

Head

Test Tape MTT-5511

Record/Playback head

Figure 2. Motor Speed Adjustment Connection Diagram

ERASE HEAD WIRE(PN201)85kHz±5kHz(Auto Reverse)

Record/Playback and Pause Mode

Unit

PN202

L201

GND

60kHz±5kHz (Auto stop)

Frequency Counter

- 2-1-

3. TUNER ADJUSTMENT

Electronic

(FM)

ItemTest PointAdjustmentAdjust for

DC VoltageCheck Point TP1, TP2L1010V±50mV

Signal Generator

FM Antenna Terminal

Unit

GND

Speaker

Figure 3. Tuner(S curve) Adjustment Connection Diagram

OSCILLOSCOPE

- 2-2-

TROUBLESHOOTING

CD PART

Turn power on.

Is power on?

Does initial read work?

Does it play?

Check the DISK circuit

YES

Check the Laser

YES

Check the focus circuit

YES

Check the TRAKING servo.

Check power supply circuit. PN508 PIN8, 6.2V PN508 PIN7, 5V IC503 PIN2, 3.3V

NONO

Check the connector PN503,

PN504, PN507

Check the tracking servo.

Does it output

audio?

- 2-3-

Check the PN508 PIN1, 3

FAILS TO INITIAL READ

Disc motor turns

YES

Does RF waveform appear?

IC501 Pin3

YES

Check the Voltage change of PN 507

NONO

PIN2(OPEN, CLOSE)

YES

Check the Data transferred from PN507

pin8 to CD DSP

YES

Check the Data transferred from PN507

pin6 to MICOM

YES

SLDO Voltage

(IC501 pin23)

YES

Check the change of SL +,

SL - Voltage

(IC502 pin 18, 19)

1.2V

0.8V

Defective connector

PN507

Defective connector

PN507, Defective

MICOM

Defective connector

PN507, Defective

IC501

Defective IC501

Defective IC502

Does laser light?

YES

Does FA+ waveform appear at

IC502 pin18?

focus coil drive wareform.

YES

Does TE waveform appear at

IC501 pin15?

TRACKING ERROR wareform

YES

Is rotation normal?

YES

Is there no dropout of RF signal?

YES

Defective contact PN503

Defective PICK-UP

Defective IC501

Defective PICK-UP

- 2-4-

Laser does not light.

Is "3.5V# applied to pin80

of IC801?

YES

Did pickup return to

innermost circular?

YES

Does it stop at inner pick circular after shift?

Is data transferred from MICOM IC ?

Does voltage appear at IC 502 pin18, 19?

Is defect output from LM SW applied to pin 5 of

YES

PN503?

OPEN CLOSE

YES

Defective MICOM.

Defective IC501, 502

Defective slide motor and/or connector.

Defective LMT SW and/or connector.

YES

Is power supplied to laser Q501?

(Q501 collector: about 1.8V)

YES

Does laser current flow? (R508!s voltage are 1.0V)

YES

R508 »1.0V

R508 «1.0V

- 2-5-

YES

Defective MICOM.

Defective connector.

Defective Q 501 and/or laser.

Defective laser and/or connector.

Laser lights

Does lens move up/down?

YES

Does FE signal appear?

(IC501 pin 13)

YES

Check the signal of FOCUS

(IC501 Pin 21)

YES

Chekc the signal of PN502

pin 13, 14

YES

Defective IC501

Defective IC502

Open activator and/or connector

Defective IC501

Does DRF signal appear?

(IC501 pin67)

- 2-6-

Degraded laser diode

Defective PICK-UP

WAVEFORMS OF MAJOR CHECK POINT

1. HF signal (RF signal ) waveform (IC501 pin4) during normal play

0.5V/Div.

(

500nS/Div.

3. Focus coil drive waveform(IC502 pin13)

When focus search failed or there is no disc on the tray

1S/Div.

(

1V/Div.

4. Tracking coil drive waveform and TE during track

traverse (1) When time division is 20mS/Div.1V/Div.

2. EFM signal (IC501 pin 3)waveform during Normal Play

0.5V/Div.

(

5µS/Div.

Focus coil drive waveform(FDO: IC501 pin21) and

DRF(IC501 pin67) when focus search is accomplished

OV (CH1)

OV (CH2)

CH1 : FOCUS COIL DRIVE

SIGNAL 2V/Div.

(

CH2 : DRF

(2) When time division 1mS/Div, 1V/Div

(During forward track traverse)

CH1 : TRACKING COIL DRIVE (IC502 pin27)

(

CH2 : TRACKING ERROR (TE: IC501 pin15)

(3) When time division is 0.5nS/div.

(During backward Track Traverse)

CH1 : TRACKING COIL DRIVE

SIGNAL 2V/Div. (IC502 pin27)

(

CH2 : TRACKING ERROR(TE: IC501 pin15)

1V/Div.

OV (CH1)

OV (CH2)

1mS/Div.

(

1V/Div.

OV (CH2)

(CH1)

(CH2)

CH1 : TRACKING COIL DRIVE (IC502 pin27)

SIGNAL 2V/Div.

(

CH2 : TRACKING ERROR (TE: IC501 pin15)

1V/Div.

5. Feed motor drive waveform(IC 502 pin18) During normal play

2S/Div.

(

0.5V/Div.

- 2-7-

P-SENS PART

Does +5V appear at ZD702?

YES

Check the pattern of

IC301 Pin .

VKK PART

Does DC - 27V appear at

PN303 Pin .

YES

Check the waveform

Check the R718 and replace

Dose -27V appear at

ZD601(-)

of D706(+).

YES

ZD 702

Replace the D706

YES

Check the TURN ON

Check the -27V(Lower) of

C603(-)

Replace the D601,

D602

Replace the Q601

Refer to power circuit

- 2-8-

POWER CIRCUIT

Check the Fuse

YES

Replace the Fuse

Check the DC output

of C715(+), C716(-)

YES

Check the DC 12V Input of

IC702

YES

Check the DC 6.2V

output of IC704

YES

Check the DC 12V

Output of IC703

YES

Check the "Collector# (5.6V)

of Q704 (CD FUNCTION)

Check the power

YES

Replace the D701, D702,

703, 704

Check the Pattern of IC702

and IC704

Check the "High# of

IC703 pin4

YES

Replace the IC703

Refer to IC401

TROUBLESHOOTING

Replace the Transformer

Check the "LOW# of

IC401 pin8

- 2-9-

MUTING CIRCUIT (MUTE)

Dose "High# appear at

Q701, Q751 "B#

YES

check the "LOW# Q701,

Q751, "C#

YES

MUTE

AUDIO ABNORMAL

Check the output of

IC701 Pin 2, 4

YES

Check the input of

IC701 pin7, 11

Refer to "IC203 Troubleshooting#

(ONLY Q201/Q251)

Check the "High# of Q702 "E#

YES

Replace the Q702

Replace the TR

Check the speaker connector

Refer to "IC301

Troubleshooting#

YES

Check the DC 10V of IC400

PIN24

YES

Check the DC 12V Output of

IC702

YES

Power check

Check the FUNCTION input

terminal

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