LG TCH-500 Service manual

STEREO CAR CD
RECEIVER

SERVICE MANUAL

MODEL : TCH-500

MODEL : TCH-500SERVICE MANUAL

P/NO : 3828REF007F

FEBRUARY, 2001

Printed in Korea

-2-

CONTENTS

SECTION 1 SUMMARY

SERVICING PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

ESD PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

LOCATION OF CUSTOMER CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

SECTION 2 ELECTRICAL

ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1. TEST & ADJUSTMENT POINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

2. FM ADJUSTMENT POINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

3. AM(MW) ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

4. LW ADJUSTMENT(OPTIONAL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

ERROR INDICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

ELECTRICAL TROUBLESHOOTING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

INTERNAL BLOCK DIAGRAM AND PIN DESCRIPTION OF IC’s . . . . . . . . . . . . . . . . . 18

BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

CIRCUIT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

1. MAIN CIRCUIT DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2. AM(MW)/TUNER/FRONT CIRCUIT DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

PRINTED CIRCUIT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

1. MAIN P.C.BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

2. TUNER P.C.BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3. FRONT P.C.BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

SECTION 3 CABINET MAIN CHASSIS & MACHANISM

• EXPLODED VIEWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

SECTION 4 REPLACEMENT PART LIST

CABINET MAIN CHASSIS & MECHANISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

ELECTRICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

-3-

SECTION 1 SUMMARY

SERVICING PRECAUTIONS

(1) Always disconnect the power source before:

1) Removing or reinstalling any component, circuit board, module or any other instrument assembly.

2) Disconnecting or reconnecting any instrument electrical plug or other electrical connection.

3) Connecting a test substitute in parallel with an electrolytic capacitor in the instrument.

CAUTION : Awrong part substitution or incorrect polarity installation of electrolytic capacitors may result

in an explosion hazard.

(2) Do not defeat any plug/socket B+ voltage interlocks with which instruments covered by this service manual

might be equipped.

(3) Do not apply power to this instrument and or any of its electrical assemblies unless all solid-state device

heat sinks are correctly installed.

(4) Always connect a test instrument’s ground lead to the instrument chassis ground before connecting the test

instrument positive lead. Always remove the test instrument ground lead last.

1) The service precautions are indicated or printed on the cabinet, chassis or components. When servicing,
follow the printed or indicated service precautions and service materials.

2) The Components used in the unit have a specified conflammability and dielectric strength. When replac­ing any components, use components which have the same ratings. Components marked in the cir­cuit diagram are important for safely or the characteristics of the unit. Always replace with the exact com­ponents.

3) An insulation tube or tape is sometimes used and some components are raised above the printed writing
board for safely. The internal wiring is sometimes clamped prevent contact with heating components.
Install them as they were.

4) After servicing always check that the removed screws, components and wiring have been installed cor­rectly
and that the portion around the service part has not been damaged. Further check the insulation
between the blades of attachment plug and accessible conductive parts.

-4-

ESD PRECAUTIONS

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 know 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 device.

(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 material).

(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 be 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 device. (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).

-5-

SPECIFICATIONS

1.RADIO SECTION

1) FM

• Frequency range ......................................................................................................87.5 ~108.0 MHz

65.0~74.0 MHz(Optional)

• Intermediate frequency.............................................................................................10.7 MHz

• Usable sensitivity ......................................................................................................10 dBµV

• Signal to noise ratio..................................................................................................60 dB

2) AM(MW)

• Frequency range ......................................................................................................522 ~ 1620 kHz or

520~1,620kHz /
530 ~ 1710 kHz(optional)

• Intermediate frequency.............................................................................................450 kHz

• Usable sensitivity ......................................................................................................28 dBµV

• Signal to noise ratio..................................................................................................50 dB

3) LW (OPTIONAL)

• Frequency range ......................................................................................................144 ~ 281 kHz

• Intermediate frequency.............................................................................................450 kHz

• Usable sensitivity ......................................................................................................35 dBµV

• Signal to noise ratio..................................................................................................50 dB

2. COMPACT DISC SECTION

• Frequency response.................................................................................................40 Hz ~ 20 kHz

• Channel separation ..................................................................................................50 dB(1 kHz)

• Signal to noise ratio..................................................................................................60 dB

3. AUDIO SECTION

• Maximum output power(per channel).......................................................................45 Watt x 4 ch

• Frequency response.................................................................................................40 Hz ~ 20 kHz

• Speaker impedance..................................................................................................4~8 Ω x 4

• Signal to noise ratio..................................................................................................60 dB

4. GENERAL

• Power requirements .................................................................................................12 ~ 15 V DC

• Ground system.........................................................................................................Negative

NOTE: Specifications are subject to change without notice in the course of product improvement.

-6-

LOCATION OF CUSTOMER CONTROLS

FRONT

Display window

TURNING ON/OFF THE UNIT

CHLOUD

MUTE RDMINTRPTDISCST

1 2 3 4

6

5789101112131516

27 18 19 20 21 22 23 24

26 25

17 14

11. (DETACH) BUTTON

12. PWR(POWER) BUTTON

13. DISC SLOT

14. LOAD EJECT BUTTON

15. FUNC(FUNCTION) BUTTON

16. AS/PS(AUTO STORE/PRESET SCAN) BUTTON

17. BAND BUTTON

18. PRESET STATION BUTTONS 1~6

19. (PLAY/PAUSE) BUTTON

10. RDM(RANDOM) BUTTON

11. RPT(REPEAT) BUTTON

12. INT(INTRO) BUTTON

13. (SKIP/SEEK) BUTTON

14. -/+ (SEARCH/TUNE) BUTTON

15. MD/LD (MODE/LOUDNESS) BUTTON

16. (MUTE) BUTTON

17. VOLUME(UP/DOWN) BUTTON

18. MUTE INDICATOR

19. ST(STEREO) INDICATOR

20. DISK INDICATOR(CDC OPTION)

21. INT(INTRO) INDICATOR

22. RPT(REPEAT) INDICATOR

23. RDM(RANDOM) INDICATOR

24. CD OPERATING INDICATOR

25. MAIN DISPLAYSECTION

26. LOUD INDICATOR

27. LEVEL INDICATOR

To turn on the unit

Press PWR or any other button
(except ).

To turn off the unit

Press PWR.

That document from http://cxema.ru

-7-

SECTION 2 ELECTRICAL

ADJUSTMENTS

1. Test & Adjustment point

<TOP VIEW>

<TOP VIEW> <BOTTOM VIEW>

L204
L254

T201

L256

T202

L205

L255

L206

C
D

A

T101

B

E VR301

Figure 1. Tuner PCB Board

Figure 2. MAIN PCB Board

-8-

2. FM Adjustment point

Stereo modulator

SSG

Power Supply

PRE OUT

VTVM

IN OUT

SCOPE

+

GND

(Black Lead)

(Red Lead)

(Yellow Lead)

-

EXT
MODE

OUT

AUDIO OSC

Unit

ANT
Jack.

Figure 3.

(1) The impedance of FM antenna terminal is 75Ω.

Therefore, connect coaxial cable (3C-2V etc.) between FM SG and antenna terminal when wiring.

(2) There are two kind in indication of FM SG output attenuator.

1) Attenuator with marking of 75Ω open...open indication type.

2) Attenuator with marking of 75Ω load or close...load or close indication type.

(3) FM SG output level in this FM adjustment are described as open indication type. The left table shows rela-

tion among FM SG attenuator indication (dB), available power ratio (dBf) and antenna terminal voltage
(dB/µV) in each indication type.

Note :

1. BAND Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FM

2. BALANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Center

3. TREBLE/BASS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Center

4. Connect as shown in figure 3.

5. Refer to figure 1~2 for Adjustment Points.

Item

Type

Open indication
type

0dB

60dB

0dB

54dB

5.2dBf

65.2dBf

11.2dBf

65.2dBf

6dB/µV

66dB/µV
12dB/µV

66dB/µV

Load or close
indication type

FM SSG

Attenuator

Indication

STEP SUBJECT

FEED SIGNAL

MEASURE OUTPUT

ADJUST-

MENT

ADJUST FOR

TOFROM

Available

Power

Ratio

Antenna
Terminal

Voltage

1

Discriminator

MPX
Adjustment

68MHz 60dB

22.5kHz Dev.
FM SSG

98MHz 60dB
75kHz Dev.
FM SSG

ANT Jack
or
Point A

Same as
above

Between Point C &

Point D , DC Volt Meter.

Between Point E ,
Frequency Counter

T101

VR301

DC 0V ± 10mV

76kHz ± 50Hz

2

-9-

3. AM(MW) Adjustment

SSG

AM Dummy ANT

PRE OUT

VTVM

IN

OUT

SCOPE

OUT

Unit

ANT
Jack.

Figure 4.

Note :

1. BAND Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AM(MW)

2. Connect as shown in figure 4.

3. Refer to figure 1~2 for Adjustment Points.

STEP SUBJECT

FEED SIGNAL

MEASURE OUTPUT

ADJUST-

MENT

ADJUST FOR

TOFROM

1

2

3

520 or
522kHz

Tuning
Voltage
Adjustment

IF Coil
Adjustment

600kHz
or 603kHz
RF
Adjustment

No Input

600kHz or 603kHz
ANT input, 30dB,
400Hz (30%MOD)
SSG

600kHz or 603kHz
ANT input, 30dB,
400Hz (30%MOD)
SG.

ANT Jack

or
Point A

Same as
above

LCD Display
(Reception Frequency)

Output L or R ch,
VTVM & Oscilloscope

LCD Display
(Reception Frequency)

Output L or R ch,
VTVM & Oscilloscope

Between Point B and
GND, DC Volt Meter

TUNE +/­Button

T201 & T202

TUNE +/­Button

L204 & L205

L206

520 or 552kHz

Max.Output

600 or 603kHz

Max.Output

DC 1.2V ± 0.05V

-10-

4. LW Adjustment(Optional)

SSG

AM Dummy ANT

PRE OUT

VTVM

IN

OUT

SCOPE

OUT

Unit

ANT
Jack.

Figure 5.

Note :

1. BAND Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LW

2. Connect as shown in figure 5.

3. Refer to figure 1~2 for Adjustment Points.

STEP SUBJECT

FEED SIGNAL

MEASURE OUTPUT

ADJUST-

MENT

ADJUST FOR

TOFROM

1

2

144kHz

Tuning
Voltage
Adjustment

150kHz
RF
Adjustment

No Input

150kHz
ANT input, 30dB,
400Hz (30%MOD)
SSG.

ANT Jack
or
Point A

LCD Display
(Reception Frequency)

LCD Display
(Reception Frequency)

Output L or R ch,
VTVM & Oscilloscope

Between Point B and
GND, DC Volt Meter

TUNE +/­Button

TUNE +/­Button

L254 & L255

L256

144kHz

150kHz

Max.Output

DC 1.2V ± 0.05V

-11-

ERROR INDICATION

INDICATION CAUSE SOLUTION(Check Point)

• Mechanism.

• Mechanism connector CN501.

• TR Q502, ZD501

• IC503 Pin 9.14.15.16.20

• IC402 Pin 46.49.50.53.54

• Mechanism.

• Mechanism connector CN501.

• TR Q502, ZD501

• IC503 Pin 7.9.14.15.16.20

• IC402 Pin 46.49.50.53.54

• Mechanism connector CN501.

• TR Q502, ZD501

• IC503 Pin 7.17.18.19.

• IC501 Pin 43

• IC402 Pin 3

• Mechanism connector CN501.

• TR Q502, Q504.Q505

• IC503 Pin 1.2.4.7.10.11.12.24.26.27

• IC501 Pin 40.48.50

• IC402 Pin 2.13.

• TR Q501

• Mechanism pick-up laser diode.

• Will disappear when the temperature return to operation
range.

• TH401

• IC402 Pin 32.

E-01

E-02

E-03

E-04

E-09

LOADING malfunction

EJECT malfunction

SLID malfunction

SERVO malfunction

HIGH Temperature

-12-

ELECTRICAL TROUBLESHOOTING GUIDE

1. No Power

ANY KEY POWER ON

YES

YES

YES

YES

YES

YES

NO

Check power supply circuitry.
Q805, Q806, Q802, IC402 Pin 33.

NO

Check Loading supply circuitry.
Q502, Q504, IC402, IC503.

NO

Check laser circuitry.
Q501, Q504, Q505, IC501, IC503

Check focusing circuitry.
IC501, IC502, IC503

Check DISC.

NO

Check tracking servo circuitry.
IC501, IC502, IC503

NO

Check audio circuitry.
IC501, IC502, IC402, IC601, IC801

Is power turned on?

DISC loading?

Does initial reading occur?

Can disc be played?

Is audio output supplied?

OK

-13-

(2) LCD light abnornal

ANY KEY POWER ON

(without DISC)

YES

NO

Check voltage in the power
supply circuitry.

YES

Is u-com IC402 reset circuit
normal? Pin36

4.8V

0V

NO

Power supply circuitry defective.
Q407, Q802, Q805, Q806

NO

Reset circuit defective.
Q403, Q404 Surrounding circuit
defective.

YES

Is u-com IC402 X1,X2 terminal
Pin 40.41 input?
OSC : 4.5MHz

NO

X401,C408,C409 defective.

YES

Is u-com IC402 keyin Pin28
5volt input?

NO

Q407,PN901,front PCB pattern
defective.

YES

Is u-com IC402 Pin61,pin62
output waveform normal?

5V

NO

IC402 pin61~64,front PCB
pattern defective.

Is IC901 com1,com2,com3
output waveform normal?

Display LCD connector defective.

5V

NO

IC901 Surrounding circuit PCB
pattern defective.

Do display LCD then light?

-14-

(3) Initial reading is not carried out(with disc)

DISC loading?

YES

NO

NO

NO

NO

NO

NO

NO

NO

Is IC402 pin54 input waveform
normal?

IC401
pin54

open close

YES

Does laser light?
CN501 pin14

YES

YES

YES YES

Is signal output at tracking
output IC501 Pin 53?

Does IC502 Pin25(LKFS) GFS
as figure?

Disc initial reading damaged or
defective.

Disc defective.

Is rotation normal?
Is there any irregularity in
frequency?

YES

Is RF signal normal without
dropout?

NO

Check voltage in the power
supply circuitry.
Q502, Q504, Q505, IC503

NO

Leaf SW contact defective.
Connector defective.
Pattern short.

NO

(A)

(B)

Does disc motor rotate?

Is RF wave output?

RF

Is tracking servo operating?
Is the lower envelope of RF
waveform flat?

Is signal output at TEO?

Is signal output at IC501
Pin50?

IC501 defective.

Pattern defective.

Connector defective.
Pick-up defective.

IC502 defective.

NO

IC502 defective.

-15-

(A) when laser does not light.

Is below signal “L” at IC501
Pin 70?

NO

NO

NO

NO NO

NO

NO

NO

YES

Slide motor defective.
Connector defective.

YES

IC503 defective.

IC501defective.

IC501 defective.
Surrounding circuitry defective

Q501 defective.
Connector defective.
Laser defective

Connector defective.
Laser defective

IC501,502 defective.

NO

NO

Reset SW defective
Connector defective.

NO

IC401 defective.

Has Pick-up returned to the
innermost position?

Does pick-up stop after having
moved to the innermost position?
IC402 Pin 3

Has laser power source returned
to the Q501?
(Q501 collector voltage about

2.2V)

Flow laser current?
Both voltage of Q501 is about

1.0V?

NO

YES

R501, 511 % 1.0V

R501, 511 & 1.0V

Are data transferred from
IC402 Pin 6, 7, 8?

Is below signal output at IC502
Pin 26,27?

Are detect output input at IC501

Pin38?