LG 42LB4D Instrucciones de funcionamiento

LCD TV - 2007

Troubleshooting

42LB4D

LCD Flat Panel

LCD TV - 2007

General Guidance

An isolation Transformer should always be used during the servicing of a receiver whose chassis is not

isolated from the AC power line. Use a transformer of adequate power rating as this protects the technician

from accidents resulting in personal injury from electrical shocks. It will also protect the receiver and it's

components from being damaged by accidental shorts of the circuitry that may be inadvertently introduced

during the service operation. If any fuse (or Fusible Resistor) in this TV receiver is blown, replace it with the

specified. When replacing a high wattage resistor (Oxide Metal Film Resistor, over 1W), keep the resistor 10

mm away from PCB. Keep wires away from high voltage or high temperature parts.

Before returning the receiver to the customer, always perform an AC leakage current check on the

exposed metallic parts of the cabinet, such as antennas, terminals, etc., to be sure the set is safe to

operate without danger of electrical shock.

Leakage Current Cold Check (Antenna Cold Check) With the instruments AC plu

removed from power

source, connect an electrical jumper across the two AC plug prongs. Place the AC switch in the on position,

connect one lead of ohm-meter to the AC plug prongs tied together and touch other ohm-meter lead in turn

to each exposed metallic parts such as antenna terminals, phone jacks, etc. If the exposed metallic part has

a return path to the chassis, the measured resistance should be between 1MΩand 5.2MΩ. When the expose

d metal has no return path to the chassis the reading must be infinite. An other abnormality exists that

must be corrected before the receiver is returned to the customer.

LCD TV - 2007

SERVICING PRECAUTIONS

CAUTION: Before servicing receivers covered by this service manual and its supplements and addenda,

read and follow the SAFETY PRECAUTIONS on page in this publication. NOTE: If unforeseen circumstances

create conflict between the following servicing precautions and any of the safety precautions in this

publication, always follow the safety precautions.

Remember: Safety First.

General Servicing Precautions

1. Always unplug the receiver AC power cord from the AC power source before;

a. Removing or reinstalling any component, circuit board module or any other receiver assembly.

b. Disconnecting or reconnecting any receiver electrical plug or other electrical connection.

c. Connecting a test substitute in parallel with an electrolytic capacitor in the receiver.

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

in an explosion hazard.

2. Test high voltage only by measuring it with an appropriate high voltage meter or other voltage

measuring device (DVM, FETVOM, etc) equipped with a suitable high voltage probe. Do not test high

voltage by "drawing an arc".

3. Do not spray chemicals on or near this receiver or any of its assemblies.

4. Unless specified otherwise in this service manual, clean electrical contacts only by applying the followin

g mixture to the contacts with a pipe cleaner, cotton-tipped stick or comparable non-abrasive applicator;

10% (by volume) Acetone and 90% (by volume) isopropyl alcohol (90%-99% strength)

CAUTION: This is a flammable mixture.

LCD TV - 2007

Unless specified otherwise in this service manual, lubrication of contacts in not required.

5. Do not defeat any plug/socket B+ voltage interlocks with which receivers covered by this service

manual, might be equipped.

6. Do not apply AC power to this instrument and/or any of its electrical assemblies unless all solid-state

device heat sinks are correctly installed.

7. Always connect the test receiver ground lead to the receiver chassis ground before connecting the test

receiver positive lead.

Always remove the test receiver ground lead last.

8. Use this receiver only with the test fixtures specified in this Training manual.

CAUTION: Do not connect the test fixture ground strap to any heat sink in this receiver.

SERVICING PRECAUTIONS

continued

LCD TV - 2007

Power Supply

Troubleshooting

LCD TV - 2007

2.5V0V3.4V on13

0V0VGND12

6.110V6V11

3.2V0VDIM10

0V0VGND9

5V5V5Vs8

2.7530.22VBRI7

3.2V0VERR6

3.2V0VI-C5

0V0VGND4

5V5V5Vs3

3.0V0VVon2

5V5VACD1

P201 RunStandby

Connector

0V0VGND10

11.990V129

0V0VGND8

3.460V3.47

0V0VGND6

6.110V65

0V0VGND4

0V0VGND3

18.860V192

18.860V191

P202 Run

Stan

dby

Connector

Power Supply Connectors

With Test unit measurements

Power Supply trouble shooting 42LB4DS Power Supply

LCD TV - 2007

3.23V0VVon/Off - 3.2Vdc12

3.27V0VADIM - 3.2Vdc11

0V0VGND10

0V0VGND9

0V0VGND8

0V0VGND7

0V0VGND6

23.93V0VVBL - +24.12VDC5

23.93V0VVBL - +24.12VDC4

23.93V0VVBL - +24.12VDC3

23.93V0VVBL - +24.12VDC2

23.93V0VVBL - +24.12VDC1

RUN modeStandbyLabelP205

BALLAST / INVERTER

2.75V0VVBR- +2.7Vdc13

3.23V0VVon/Off - 3.2Vdc12

3.27V0VADIM - 3.2Vdc11

0V0VGND10

0V0VGND9

0V0VGND8

0V0VGND7

0V0VGND6

23.93V0VVBL - +24.12VDC5

23.93V0VVBL - +24.12VDC4

23.93V0VVBL - +24.12VDC3

23.93V0VVBL - +24.12VDC2

23.93V0VVBL - +24.12VDC1

Run ModeStandbyLabelP204

BALLAST / INVERTER

Power Supply Ballast Connectors

With Test unit measurements

Power Supply trouble shooting

LCD TV - 2007

1 KOhm*24V1.2 KOhm*24V

0GND0GND

∞

BRT CTRL

1 KOhmBRT CNTRL

∞

INV. CTRL

93.4 KOhmINV. CNTRL

10.9 KOhm3.4V_ON10.9 KOhm3.4V_ON

0GND

0GND0GND0GND

0GND

1.3 KOhm*6V0GND1.3 KOhm*6V

1 KOhm*12V

0GND

∞

PWR_DN

1 KOhm*12V0GND5.5 KOhmPWR_DN

1 KOhm*12V

.7 KOhm*12V0GND1 KOhm*12V.7 KOhm*12V0GND

0GND

0GND5.5 MOhm*5V_STB0GND0GND4 MOhm*5V_STB

0GND

1 KOhm*3.4V

∞

BT_CNTRL

0GND1 KOhm*3.4V99.7 KOhmBT_CNTRL

1 KOhm*6V

0GND

∞

ERR_OUT

1 KOhm*6V0GND

∞

ERR_OUT

1 KOhm*6V1.3 KOhm*8V

∞

INV_CTRL

1 KOhm*6V1 KOhm*8V93.4 KOhmINV_CTRL

0GND

0GND0GND0GND0GND0GND

0GND

0GND8 MOhm*STB0GND0GND7 MOhm*STB

1 KOhm*3.4V

2 KOhm*19V

∞

PWR_NF

1 KOhm*3.4V1.7 KOhm*19V

∞

PWR_NF

1 KOhm*3.4V2 KOhm*19V

∞

AC_DET

1 KOhm*3.4V1.7 KOhm*19V100.7 KOhmAC_DET

P200

P201P202P200P201P202

Resistances with Board Disconnected

Resistances with Board Connected

47LB1DA POWER SUPPLY

LCD TV - 2007

+12.0V

+6.0V

CS4344

CS4344 CS5340

CS5340

PQ05DZ1U

KIA78R09

KIA78R09 KIA78R09

KIA78R09

MC33078

X260

HYB18T512(4EA)

AZ1117H-1.8

AZ1117H-1.8 LM75

LM75

ICL3232CBNZ

+5.0VST

+3.3V_L

AT/NT Tuner

+5V_L

+5.0V

SI3865

PQ05DZ1U

Standby Power

Run Power

Live-on

AZ1117H-3.3

AZ1117H-3.3 LGDT3703(MAIN)

LGDT3703(MAIN)

SC1565-1.8

SC1565-1.8 ISL6549CB

ISL6549CB

1.2V

1.8V

ISL6549CB

ISL6549CB 1.8V MK3727D

MK3727D 74LVT16373(2EA)

74LVT16373(2EA) S29GL256

S29GL256

THC63LVD1023

+3.3V_L

HYB18T512(4EA)

HYB18T512(4EA) MK3727D

MK3727D

+19.0V

+19.0V NTP3000

NTP3000

1.8V

BA033FP-3.3

BA033FP-3.3 MTV416

MTV416

AZ1086-1.8

AZ1117H-3.3

SC1565-2.5

SC1565-2.5 MST3369

MST3369

9.0V

TEA6420

9.0V

CS8416

KIA78R09

MK3727D

MIC2505

3.3VST_MICOM

24C08

FRC94XYH

Live-on

24C512

STMAV335

ISP1504

MIC2505

KIA7805

AZ1085S-3.3

AZ1085S-1.8

AZ1085S-1.8 24C16

24C16

FRC

SC1565-2.6

SC1565-2.6 MIC3910-2.5

MIC3910-2.5

SC1592-1.0

12.0V

HY5DU281622

SC2595-1.0

Power Supply Voltage Distribution Diagram

LCD TV - 2007

ATI

(X260)

I2C Master

AT/NT Tuner

0xC2

HDMI

ADC

(MST3361)

0X9C

Temp.

Sensor

(LM75)

0X94

U-Com

(MTV416)

0x50

I2C_CH1 (+3.3V_L & +5V_L)

I2C_CH2 (+3.3V_L & +5V_L)

I2C_CH3 (+3.3V_L)

Port

Expander

(M62320)

0X74

Audio

Switch

(MSP4450K)

0X80

DASP

(NTP3000)

0X54

PDP Module

0x1C

VSB/QAM

(LGDT3703)

Main

0X1C

Live Dead

CS8416A

0X20(W)

0X21(R)

EEPROM

(24LC512)

0xA6

CH1

CH2

CH3

FRC94XYH

0xD4

EEPROM

(24LC16)

5V 5V

2.5V

I²C Bus Controller Block Diagram

Stand-By Power Operation

Power Supply trouble shooting

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