LG LM-230 Service manual

- 1-1 -

CONTENTS

SECTION 1. GENERAL

• SERVICING PRECAUTIONS

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

1-2

• ESD PRECAUTIONS

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

1-4

• SPECIFICATIONS

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

1-5

SECTION 2. ELECTRICAL

• ADJUSTMENTS

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

2-1

• TROUBLESHOOTING

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

2-3

• WAVEFORMS OF MAJOR CHECK POINT

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

2-7

• BLOCK DIAGRAM

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

2-17

• SCHEMATIC DIAGRAMS

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

2-19

• WIRING DIAGRAM

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

2-27

• PRINTED CIRCUIT DIARGAMS

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

2-29

• INTERNAL BLOCK DIAGRAM OF IC’s

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

2-38

• REPAIRS REGARDING CD MECHANISM

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

2-45

SECTION 3. EXPLODED VIEWS

• CABINET AND MAIN FRAME SECTION

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

3-1

• TAPE DECK MECHANISM: AUTO STOP DECK(OPTIONAL)

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

3-3

• TAPE DECK MECHANISM: AUTO REVERSE DECK

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

3-5

• CD MECHANISM

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

3-7

SECTION 4. SPEAKER

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

4-1

SECTION 5. REPLACEMENT PARTS LIST

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

5-1

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.

- 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

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 (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.

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.

- 1-3 -

Armband

Conductive Sheet

Resistor (1 Mohm)

VOLUME KNOB

DOWN

VOLUME

RESET jump wire

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 -

- 2-1 -

TAPE DECK ADJUSTMENT

1. AZIMUTH ADJUSTMENT

Figure 1. Azimuth Adjustment Connection Diagram

CH1 CH2

Speaker Out

Playback Mode

Head

Test Tape MTT-114

L ch

R ch

GND

Dual-trace synchroscope

Electronic Voltmeter

L out

R out

Unit

SECTION 2. ELECTRICAL

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.

Deck Mode Test Tape Test Point Adjustment Adjust for

A Deck Playback MTT-114 Speaker Out

DECK Screw

Maximum

Azimuth Screw

B Deck Playback MTT-114 Speaker Out Azimuth Screw Maximum

2. MOTOR SPEED ADJUSTMENT

Figure 2. Motor Speed Adjustment Connection Diagram

Head

Playback Mode

Unit

Speaker Out

GND

L out

R out

Record/Playback head

Test Tape MTT-111

Frequency Counter

Deck Mode Test Tape Test Point Adjustment Adjust for Remark

Normal Speed MTT-111 Speaker Out VR201 3kHz ± 1% A Deck

HI-Speed MTT-111 Speaker Out more than 5.4kHz HI-Speed Dubbing Mode

- 2-2 -

3. RECORD BIAS ADJUSTMENT

Head

Unit

PN202

GND

Record/Playback head

Test Tape MTT-5511

Record/Playback and Pause Mode

Frequency Counter

Deck Mode Test Tape Test Point Adjustment Adjust for

Rec/Pause MTT-5511

ERASE HEAD

L203

60kHz±5kHz (Auto stop)

WIRE(PN202) 85kHz±5kHz(Auto Reverse)

Figure 3. Record Bias Adjustment Connection Diagram

- 2-3 -

TROUBLESHOOTING

Turn power on.

Is power on?

Does initial read work?

Does it play?

Does it output audio?

Check power supply circuit. PN807 PIN5, 6.2V PN807 PIN7, 5V IC803 PIN 2, 3.3V

Check the connector

PN801, PN802, PN809

Check the tracking servo circuit.

Check the PN807 PIN1, 3

YES

NONO

Check the DISK turns

Check the Laser

Check the focus circuit

Check the TRAKING circuit

- 2-4 -

FAILS TO INITIAL READ

1.2V

0.8V

NO NO

YES

Disc motor turns

Does RF waveform appear?

IC801 Pin3

Check the Data transmission from

PN809 pin11 to CD DSP

Check the Data transmission from

PN809 pin13 to MICOM

Check the change of SLDO

Voltage(IC801 pin23)

Check the change of SL +,

SL - Voltage

(IC802 pin 18, 19)

Check the Voltage change of PN 809

PIN20(OPEN, CLOSE)

Defective connector

PN809

Defective connector

PN809, Defective

MICOM

Defective connector

PN809, Defective

IC801

Defective IC801

Defective IC802

Defective contact PN802

Defective PICK-UP

Does laser light?

focus coil drive wareform.

TRACKING ERROR wareform

Is rotation normal?

Defective IC801

Defective PICK-UP

Is there no dropout of RF signal?

Does FA+ waveform appear at

IC802 pin13?

Does TE waveform appear at

801 pin 15?

- 2-5 -

A

Laser does not light.

Is “3.5V” applied to pin of IC 801?

Is power supplied to laser Q801?

(Q 801 collector: about 1.8V)

Does laser current flow?

1.0V across R808

Is data transferred from MICOM IC ?

Does voltage appear at IC 802 pin 17, 18?

Defective MICOM.

Defective connector.

Defective IC 801, 802

Defective slide motor and/or connector.

Defective LMT SW and/or connector.

Defective Q 801 and/or laser.

Defective laser and/or connector.

Did pickup return to

innermost circular?

Does it stop at inner pick circular after shift?

Is defect output from LM SW applied to pin 2 of PN802?

R808

»1.0V

R808

«1.0V

YES

OPEN

YES

- 2-6 -

YES

Laser lights

Does lens move up/down?

Check the signal of

FOCUS SEARCH

(IC801 Pin 21)

Chekc the signal of PN802

pin 13, 14

Does FE signal appear?

(IC801 pin 13)

Does DRF signal appear? (IC 801 pin67)

Defective IC801

Defective IC802

Open activator and/or connector

Defective IC801

Degraded laser diode

Defective PICK-UP

- 2-7 -

(CH1)

(CH2)

1. HF signal (RF signal ) waveform

(IC801 pin 3) during normal play

2. EFM signal (IC801 pin 3)waveform during Normal Play

3. Focus coil drive waveform(IC802 pin13)

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

• Focus coil drive waveform(FDO: IC801 pin21) and DRF(IC801 pin67) when focus search is accomplished

4. Tracking coil drive waveform and TE during track traverse (1) When time division is 20mS/Div.1V/Div.

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

(During forward track traverse)

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

(During backward Track Traverse)

5. Feed motor drive waveform(IC 802 pin18) During normal play

CH1 : FOCUS COIL DRIVE

SIGNAL 2V/Div.

CH2 : DRF

CH1 : TRACKING COIL DRIVE

SIGNAL 2V/Div. (IC802 pin27)

CH2 : TRACKING ERROR(TE: IC801 pin15)

1V/Div.

(

CH2 : TRACKING COIL DRIVE (IC802 pin27)

SIGNAL 2V/Div.

CH2 : TRACKING ERROR (TE: IC801 pin15)

1V/Div.

(

CH1 : TRACKING COIL DRIVE (IC802 pin27)

CH2 : TRACKING ERROR (TE: IC801 pin15)

(

0.5V/Div. 500nS/Div.

(

1S/Div. 1V/Div.

(

1mS/Div. 1V/Div.

(

0.5V/Div. 5µS/Div.

(

2S/Div.

0.5V/Div.

OV (CH1)

(CH2)

(CH1)

(CH2)

WAVEFORMS OF MAJOR CHECK POINT

- 2-8 -

VKK PART

Does DC - 33V appear at

CN302 Pin .

Check the Voltage of IC301

pin51

Dose -33V appear at

ZD902(-)

Check the Q903

TURN ON

Check the PATTERN

Replace the ZD902

Replace the Q903

Refer to power circuit

END

Check the -33V(LOWER)

of C916

Replace the D704,

D705

YES

P-SENS PART

Does +5V appear at ZD901?

Check the pattern of

IC301 Pin .

Check the waveform

of D913(cathod).

Check the R768 and

replace ZD901.

Replace the D703

YES

- 2-9 -

POWER CIRCUIT

Check the Fuse

Check the DC output

of C901(+), C902(-)

Check the DC Output of

C930(+)

Check the Voltage

output of IC901, IC902

Check the DC 12V

Output of IC903

Check the 5V of CN513

pin 7(CD FUNCTION)

END

Replace the Fuse

Check the AC Output of

CN901 pin1, 5

Check the AC Output of

CN701 PIN 9, 10

Replace the IC904

Replace the D901, D902,

D903, D904

Replace the D706, D707,

D708, D709

Check the IC901, IC902

Check the 5V of

IC301 pin78

Check the “Low” of Q904“B”

Check the Q904, CD Ass’y

Check the power Ass’y or

Replace the Transformer

Check the power Ass’y

or Replace the

Transformer

Check the 5V of IC301

PIN13& PN302,

CN302, PIN13

Check the HIGH of

Q905 “B” and Replace

Check the “High” of

IC501 pin 14

Check the IC501

YES

- 2-10 -

AUDIO ABNORMAL

Check the output of

IC601 Pin 12, 17

Refer to “IC601

Troubleshooting”

Refer to “Muting

Troubleshooting”

Check the 10V(Higher) of

IC601 pin 5 & Check

the power circuit

Check the input of

IC701 pin3

Check the Output of

IC701, pin14

END

YES

Muting circuit (MUTE)

Dose “Low” appear at

Q702 “B”

Check the “High” of Q701,

Q751 “B”

MUTE

Check the connector of

Q702 “B” and GND

Replace the TR

YES

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