LG LM-M540 Service Manual

- 1-1 -

[CONTENTS]

❍ SECTION 1. GENERAL

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

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

❍ SECTION 2. ELECTRICAL SECTION

• ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

• ELECTRICAL TROUBLESHOOTING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

• INTERNAL BLOCK DIAGRAM of ICs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

• BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31

• SCHEMATIC DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

• WIREING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-45

• PRINTED CIRCUIT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-47

❍ SECTION 3. EXPLODED VIEWS

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

• TAPE DECK MECHANISM (A/R & A/S : LEFT A/S DECK) . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

• TAPE DECK MECHANISM (A/R & A/S : RIGHT A/R DECK) . . . . . . . . . . . . . . . . . . . . . . . . . .3-5

• CD MECHANISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

❍ SECTION 4. SPEAKER PART

• SPEAKER PART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

❍ SECTION 5. REPLACEMENT PARTS LIST

• REPLACEMENT PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

- 1-2 -

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

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.

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.

Resistor
(1 Mohm)

Conductive
Sheet

Resistor
(1 Mohm)

Armband

RESET jump wire

VOLUME

VOLUME KNOB

DOWN

UP

- 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 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 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.

- 2-1 -

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.

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

Deck Mode Test Tape Test Point Adjustment Adjust for

Palyback MTT-114 Speaker Out

DECK Screw

Maximum

Azimuth Screw

- 2-2 -

❏ ELECTRICAL TROUBLESHOOTING GUIDE

■ AUDIO PART

P-SENS PART CHECK

ZD 901(5V) Voltage check

IC301 26PIN PATTERN Check

Half-wave rectification wave form check

R783 check, then ZD901 replacement

D713 Replacement

VKK CHECK

CN302 28pin DC -33V check

IC301 51PIN check

ZD902 -33V check

Q903 turn on check

Pattern disconnection check

D912, D911 replacement

normal

ZD902 replacement

Refer to power

supply check

C916 -33V and less check

Q903 replacement

- 2-3 -

POWER CHECK

Every kinds of Fuse check

C901(+), C902(-) DC power output check

C903(+) DC power output check

IC901, IC902 power output check

IC903 power output check (12V)

CN513 7PIN 5V check (at CD Function)

normal operation

Fuse replace

CN901 1, 5 AC voltage output check

D901 replacement

Power supply Ass’y check
and transformer replacent

IC301 5V Power output
PN302/CN302 13 PIN check

Check

IC5019BU2090 check & replace

IC501(BU2090) 14PIN HIGH check

Q905 Base HIGH(C103M)
Check and replace defective

Power supply Ass’y check
and transformer replacent

CN901, 9, 10 pin DC power output check

IC901, IC902 check and replacement

D902, D903, D904, D905 (1SR35)
check and replacement

IC301 78PIN 5V check

IC904 replacement

Q904(A1273) Base Low check

Q904, CD Ass’y check replacement

- 2-4 -

Muting circuit Troubleshooting (if MUTE)

Q702(A102) Base “LOW”

Q701, Q751(IC302) Base “LOW” check

MUTE

Q702 Base and GND operation
status check

Refer to IC601(TDA7468D) IC specification

Refer Muting troubleshooting

Refer SPK replay troubleshooting

IC701 12PIN (over 2V) check and power
supply circuit check

No sound

IC 601 12, 27 PIN Output check

IC701 input check (14PIN)

IC701 output check (6PIN)

RY701 check

normal

- 2-5 -

SPK Relay Troubleshooting

D704(+) 12V check

Q704 Collector “Low” check

Output check

normal operation

Refer power check

Q704 Base “High”

Q704 Replacement

RELAY Replacement
(RY701)

Refer IC501(BU2090) Troubleshooting

AUX

IC601 5, 24 PIN signal input check

JK600 signal input check

Specific FUNCTION MODE has no sound

TAPE

IC601 3,26 PIN signal input check

Refer IC202 Troubleshooting

- 2-6 -

CD

IC601 6,23 PIN signal input check

CN513 1,3 PIN signal check and refer to CD Troubleshooting

TUNER

IC601 4, 25 PIN signal input check

Refer TUNERMODULE

MIC

IC602 2PIN check

Refer to IC404 Troubleshooting

IC301 Troubleshooting

C301 17, 46, 72, 90 power applied check

IC301 26PIN 5V applied check

X301 oscilates or not

When IC301 11Pin voltage input. High➞Low➞High

IC301 replace

Refer to power supply check

P-SENS terminal check

X301 replacement

RESET circuit check

- 2-7 -

IC501 Troubleshooting

IC501 16PIN power applied check

IC501 2, 3 PIN CLK Data check

CONTROL function check

normal

Refer to IC301 Troubleshooting

Refer to power supply check

IC501 replace Pattern check between IC301 and IC501

IC301 3,4 PIN data check
(When switched to CD, TAPE Function)

IC601(TDA7468D) Troubleshooting

IC601 1PIN power applied check

IC601 7,22 Pin waveform output check

IC601 8,21Pin waveform input check

IC601 12,17Pin waveform output check

normal

IC601 15,14 Pulse waveform check
(with tunning VOL DIAL)

Refer to power supply check

IC301 76,75, 5, 10 Pin check

IC601 replacement

MICOM(82,83) - IC401(21,22) Pattern checkIC601 replace

IC301 Troubleshooting

- 2-8 -

IC701, IC751 Troubleshooting

3PIN signal input check

8, 15Pin(-), 7, 13Pin(+) voltage check

14 Pin signal output check

OK

Refer to Muting circuit

Refer to power supply check

9, 10PIN power check (over 5V)

PLAY check

IC202 18Pin VCC power applied

IC202 5,20 Pin signal output check

Muting circuit check

Refer to power supply check

Deck Mecha operation performance check

Deck Mecha replace

IC202 replacement

- 2-9 -

Rec check (Q252, Q202 ON : R273, R223 High)

IC202 11,14PIN signal input check

IC202 9,16 Pin signal input check

IC201 6(12V), 4 Pin High check

L203 2,3PIN oscilation check

Deck replacement

Q253, Q203 Base "Low" check

Q253,Q203 replacement

Refer to IC203 Troubleshooting

IC202 18Pin VCC voltage check

Power check, IC203 Troubleshooting check

C236(+) power supply check

Refer to power supply check

IC203 Troubleshooting check

Q208 replacement

L203 replacement

Q208 Base 0.6V supplied check

Q208 Collector Low

Q207 replace

normal

Dubbing check ("NORMAL or REC"//"HIGH")

Q252, 202 "OFF"//"ON" : R273,223 "Low"//"HIGH"

Q253,203 "ON"//"OFF"

Refer to REC Check

IC203 Troubleshooting check

- 2-10 -

■

CD PART

TURN ON CD

CONNECTOR CHECK ( PN808,PN807 )

CHECK POWER SUPPLY CIRCUIT( PN808 )

CHECK MICOM INTERFACE CIRCUIT( PN807 )

CHECK MICOM INTERFACE CIRCUIT( PN807 )

CONNECTOR CHECK(PN801,PN802)

CHECK PICKUP MOVEMENT

CHECK BA5810FP (IC803)

CHECK MN6627933CG (IC801)

CHECK AN22004 (IC802)

CONNECTOR CHECK (PN808)

CONNECTOR CHECK

( PN808,PN807,PN802,PN801 )

OPEN CLOSE CHECK

“ READING ”

DISPLAY CHECK

READING OK CHECK

IF PLAY, AUDIO

OUTPUT CHECK

OK

YES

YES

YES

YES

YES

NO

NO

NO

NO

- 2-11 -

OPEN CLOSE NG

NO

NO

NO

NO

CONNECTOR LOCKING CHECK ( PN808,PN807 )

DEFECTIVE MAIN

POEWR SUPPLY

DEFECTIVE MICOM

DEFECTIVE IC803

DEFECTIVE

MECHANISM

CHECK POWER SUPPLY CIRCUIT( PN808 ,PN807)

PN808 PIN 5 = 6.2V, PIN 7 = 5V

PN807 PIN 1 = 5V

CHECK VOLTAGE CHANGE OF OPEN CLOSE ,

AND BTLMUTE VOLTAGE(= 5V)

(PN807 PIN 20:OPEN, 19:CLOSE, 4:BTLMUTE)

CHECK VOLTAGE CHANGE LO+, LO- OF IC803

(PN807, PIN OPEN:20, CLOSE:19)

YES

YES

YES

- 2-12 -

READING DISPLAY CHECK (= ONLY “CD “DISPLAY)

CONNECTOR LOCKING CHECK

(PN808,PN807,PN802,PN801 )

DEFECTIVE CONNECTOR OR

MAIN POWER SUPPLAY

DEFECTIVE IC805

DEFECTIVE MICOM OR

CONNECTOR

CHECK RESET SIGNAL OF PN807

PN807 PIN12 : 5V

CHECK VOLTAGE THE PIN 2 OF IC805

IC805 PIN2 : 3.3V

DEFECTIVE MICOM OR

CONNECTOR

DEFECTIVE IC801

CHECK MICOM INTERFACE

CIRCUIT( PN807 )

PN807 PIN 11,13,14,15 SIGNAL CHECK

(11: STAT, 13: MDATA, 14:MCLK, 15:MLD)

CHECK THE WAVE FORM #1

CHECK POWER SUPPLY

PORT( PN808 ,PN807)

PN808 PIN 5 = 6.2V, PIN 7 = 5V

PN807 PIN 1 = 5V

YES

YES

NO

NO

NO

NO

NO

YES

YES

YES

- 2-13 -

AAAA

BBBB

CCCC

DDDD

EEEE

READING OK CHECK (= “NO DISC” DISPLAY)

CONNECTOR LOCKING

CHECK(PN801,PN802)

DOES SLED MOVE ?

DOES LENSE MOVE ?

(= UP & DOWN)

DOES LASER LIGHT ?

DOES SPINDLE ROTATE ?

IS READING OK ?

CHECK PN801 PIN 14,15

(TA- ,TA+)

CHECK PN802 PIN

5,6( SP+,SP-)

CHECK PN802 PIN 10( LD )

CHECK PN801 PIN 13,16

( FA-, FA+)

CHECK PN802 PIN 3,4( SL+,SL-)

DEFECTIVE PICKUP OR

IC803 OR IC801 OR IC802

DEFECTIVE PICKUP OR

IC803 OR IC801

DEFECTIVE PICKUP OR

IC802

DEFECTIVE PICKUP OR

IC803

DEFECTIVE PICKUP OR

IC803 OR IC801 OR IC802

NO

NO

NO

NO

NO

YES

YES

YES

YES

YES