LG CD-372A User manual

- 1-1 -

❍

SECTION 1. SUMMARY

• SERVICING PRECAUTIONS

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

1-2

• ESD PRECAUTIONS

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

1-4

• SPECIFICATIONS

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

1-5

❍

SECTION 2. ELECTRICAL SECTION

• ADJUSTMENT

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

2-1

• TROUBLESHOOTING GUDIE

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

2-2

• INTERNAL BLOCK DIAGRAM OF IC’s

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

2-11

• IC VOLTAGE SHEET

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

2-16

• BLOCK DIAGRAM

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

2-20

• SCHEMATIC DIAGRAMS

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

2-22

• WIRING DIAGRAMS

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

2-36

• PRINTED CIRCUIT BOARD DIARGAMS

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

2-38

❍

SECTION 3. EXPLODED VIEWS

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

3-1

❍

SECTION 4. REPLACEMENT PARTS LIST

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

4-1

[CONTENTS]

❏ SERVICING PRECAUTIONS

[NOTES REGARDING HANDLING OF THE PICK-UP]

➊ 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.

➋ 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.

- 1-2 -

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

Pressure

Cotton swab

Conductive Sheet

SECTION 1. SUMMARY

[NOTES REGARDING COMPACT DISC PLAYER REPAIRS]

➊ 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.

➋ 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 (1MΩ)

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.

- 1-3 -

Armband

Conductive

Sheet

Resistor

(1 Mohm)

Resistor

(1 Mohm)

❏ 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]

- 1-4 -

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 -

❏ SPECIFICATIONS

* Designs and specifications are subject to change without notice for improvement.

- 2-1 -

❏ ADJUSTMENT

1.AM ADJUSTMENT

SECTION 2. ELECTRICAL SECTION

STEP ITEM SSG OUTPUT SET FREQUENCY ADJUSTMENT ADJUST FOR

1 IF 450KHz 522(530)KHz T102 Maximum

2 VT --- 1611(1610)kHz T101 5.5V

3 SENSITIVITY 603(600)kHz 603(600)kHz L103 Maximum

4 SENSITIVITY 1404(1400)kHz 1404(1400)kHz TC101 Maximum

5 Repeat steps 3 and 4 for several times

2.FM ADJUSTMENT

STEP ITEM SSG OUTPUT SET FREQUENCY ADJUSTMENT ADJUST FOR

1 VT --- 108MHz L102 5.0V

2 SENSITIVITY 90MHz 90MHz L101 Maximum

3.TAPE DECK ADJUSTMENT

DECK MODE TEST TAPE TEST POINT ADJUSTMENT ADJUST FOR

BLAY BACK MTT-114 L/R Output Azimuth adjusting screw L/R Maximum

4.RECORD BIAS ADJUSTMENT

DECK MODE TEST TAPE TEST POINT ADJUSTMENT ADJUST FOR

REC MODE MTT-5511 JW427 T401 68KHz±2KHz

- 2-2 -

CD PART

Check power supply circuitry.

Is audio output supplied?

Can disc be played?

Check laser circuitry.

Check focusing circuitry.

Check tracking servo circuitry.

Check Audio circuitry.

Check disc.

Is the function selector in the CD

position?

Is power turned ON?

Does initial Reading occur?

OK

END

NO

YES

❏ TROUBLESHOOTING GUIDE

1] CD PART

• CD CIRCUIT

- 2-3 -

(1) If display LCD lighting is abnormal

Is the function selector in

the CD position?

Do display LCD then light?

Check voltage in the power

supply circuitry.

(WITHOUT DISC)

•

X701 defective.

• Reset circuit defective.

• Surrounding circuit

defective.

•

Power supply circuitry

defective

•

Check Q516 and CN603

Is IC201 Pin51 52 53 54 to

72 output waveform normal?

Is µ-COM reset circuit

nomail

micom

VDD

Is µ-COM 701pin14 and 15

(OSC) input?

•

Pattern defective.

•

Display defective.

NO NO

NO

YES

RESET 0V

0V

3V

About 0.125

µ

sec

CD FUNCTION

YES

- 2-4 -

(2) If initial reading is not carried out(with Disc)

Is IC201 Pin42 output

waveform normal?

•

Limit SW contact defective.

•

Connector depective.

•

Patter short.

Dose disc motor rotate?

•

IC 601

defective.

•

Connector

defective.

•

Pick up

defective

Is TER signal

output at IC601

pin34 ?

•

Pattern

defective.

•

IC 603

defective.

•

Pick up

defective

•

Connector

defective.

•

IC 601

defective.

Dose IC601 pin20 (LOCK) as figure?

Is HF wave-

form output?

IC601 pin 2

Is tracking servo

operating?

Is the lower IC601

pin2 waveform flat?

Is signal output at

IC601 pin29

Is rotation normal?

Is there any irregularity in

frequency?

Is HF signal normal without

dropout?

•

Disc initial reading

damaged defective.

•

Pick up defective.

Dose laser light?

Is signal output at tracking output IC603

pin26 ,27 ?

YES

Door open

Door close

LOW

YES

NO

NONO

NO NO

3~4V

0V

NO

A

B

- 2-5 -

When laser does not light

Does lenses move up and down?

•

IC701 defective.

•

IC 601, 603 defective.

•

Slide motor defective.

•

Connector defective.

Is below signal output at

IC603 Pin17,18 ?

Does pick-up stop after having

moved to the innermost

position?

Dose generate about 2.5V at

IC601 Pin18 (LD)?

Has laser power source returned to

the Q601

(Q601 collector voltage about 1.8V)

Flow laser current?

Both voltage of R610 is about 0.7V?

R610

» 0.7V

R610 « 0.7V

•

Laser defective.

•

connector defective, short etc.

•

Q601 defective, connector

defective.

•

Laser defective.

•

Connector defective.

•

IC601 defective.

•

Surrounding Circuitry defective.

•

connector defective.

•

IC602 defective.

•

IC603 defective.

Has Pick-up returned to the

innermost position?

Are data transterred from

IC 701?

NO NO

NO

YES

A

- 2-6 -

When laser light

Does lenses move up and down?

•

IC701 defective.

•

IC 603 defective.

•

Actuator short.

•

Connector OPEN.

•

Connector short.

•

IC601 defective.

•

Pick-up defective.

• Turntable height error.

• Laser diode degraded.

•

IC 601 defective.

•

Pattern defective.

Is Fok signal output?

IC101 Pin2 0.4V over OK.

Is Fok signal input to IC601

Pin13 ?

The waveform of IC601 pin2 Is

below figure?

Is IC601 pin2 signal waveform

output?

Is signal output at focus

search terminal?

Is signal output at IC601

1, 2?

NO NO

NO

Amplitude

0.5~1.5V

NO

YES

B

C

- 2-7 -

C

Is FSL signal Output?

IC601 pin13

• IC701 defective.

•

Pick-up defective.

•

Connector defective.

•

Pattern defective between

•

IC602 Pin18 19 20 21 and

IC701

When Fok focus

Servo Conform

by FEO signal.

•

IC 601 defective.

Is FEO signal output at IC601

Pin31 ?

Is SMDS signal output

by IC602 Pin13 ?

Is SMPD signal output by

IC602 Pin12 ?

Has voltage at disc motor?

•

IC601, 603 defective.

•

Surrounding circuitry

defective.

• Disc Motor defective.

• Connector defective.

YES

At start

NO

FEO

- 2-8 -

Is the function selector

In the TUNER position?

Is u-com reset circuit normal?

Is u-com IC701 #17 pin and

#18 (OSC) input?

IC 701 #51,52,53 output Wave

Form Normal?

2] LCD PART

• LCD CIRCUIT

If display LCD lighting is abnormal

- 2-9 -

A. MAIN

B. TUNER

No Power at IC351 Pin 4,8

Is B+ applied

to PN501?

Check Q501,502 and Q503

Check Fuse(F501, F502)

Is there a DC voltage

at the (+)terminal of

D501~D504

Replace D501~D504

Replace PN 501

TUNER ABNORMAL.

Is B+ applied to

R137,141?

Check IC101,102

Check Q510,511

Is there a DC Voltage

at the Q517,518

Replace IC101

YES

NO

3] MAIN PART

• MAIN CIRCUIT

- 2-10 -

D. TAPE REC

C. CASSETT DECK

DECK ABNORMAL.

Is B+ applied to Q504?

Is DECK LEAF SW normal?

Check PN402.

Replace LEAF SW.

Check SW402.

Is there a DC voltage at

the Collector terminal

of Q504

Replace Q504

TAPE REC ABNOMAL.

Is oscillation

of L401 normal?

Check S401 and Q402.

Replace L401.

YES YES

YES

NO

- 2-11 -

❏ INTERNAL BLOCK DIAGRAM OF ICs

■ LC72131

• Block Diagram

• Pin Assignments (Top View)

- 2-12 -

• Pin Assignments (Top View)

■ TDA7440D

• Block Diagram

- 2-13 -

■ S3C8248

• Block Diagram

• Pin Assignments (Top View)

- 2-14 -

■ TA2149BN

• Block Diagram

■ KIA8207K(TA8207K)

• Block Diagram

- 2-15 -

■ TDA2104(MP3 DECODER)

• Block Diagram

• Pin Assignments (Top View)

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LG CD-372A User manual

LG CD-372A User manual

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