LG 43LJ553T, 43LJ55 Schematic

LED TV

SERVICE MANUAL

CHASSIS : LA75M

MODEL : 43LJ55** 43LJ55**-U*

CAUTION

BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

P/NO : MFL69963002 (1703-REV01)

CONTENTS

CONTENTS .............................................................................................. 2

SAFETY PRECAUTIONS ........................................................................ 3

SERVICING PRECAUTIONS ................................................................... 4

SPECIFICATION ....................................................................................... 6

SOFTWARE UPDATE .............................................................................. 8

BLOCK DIAGRAM ................................................................................... 9

EXPLODED VIEW .................................................................................. 10

DISASSEMBLY GUIDE .......................................................................... 11

TROUBLE SHOOTING GUIDE ................................................ APPENDIX

- 2 -

SAFETY PRECAUTIONS

IMPORTANT SAFETY NOTICE

Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in the Exploded View. It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent Shock, Fire, or other Hazards. Do not modify the original design without permission of manufacturer.

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 1 W), 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 damage of electrical shock.

Leakage Current Cold Check(Antenna Cold Check)

With the instrument AC plug removed from AC 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 1 MΩ and 5.2 MΩ. When the exposed 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.

Leakage Current Hot Check (See below Figure)

Plug the AC cord directly into the AC outlet.

Do not use a line Isolation Transformer during this check. Connect 1.5 K / 10 watt resistor in parallel with a 0.15 uF capacitor between a known good earth ground (Water Pipe, Conduit, etc.) and the exposed metallic parts. Measure the AC voltage across the resistor using AC voltmeter with 1000 ohms/volt or more sensitivity. Reverse plug the AC cord into the AC outlet and repeat AC voltage measurements for each exposed metallic part. Any voltage measured must not exceed 0.75 volt RMS which is corresponds to

0.5 mA. In case any measurement is out of the limits specified, there is possibility of shock hazard and the set must be checked and repaired before it is returned to the customer.

Leakage Current Hot Check circuit

- 3 -

SERVICING PRECAUTIONS

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

SAFETY PRECAUTIONS on page 3 of this publication. NOTE: If unforeseen circumstances create conict between the

following servicing precautions and any of the safety precautions on page 3 of 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 mod-

ule 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 specied otherwise in this service manual, clean

electrical contacts only by applying the following 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 ammable mixture. Unless specied 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 with this receiver only the test xtures specied in this

service manual.

CAUTION: Do not connect the test xture ground strap to any

heat sink in this receiver.

Electrostatically Sensitive (ES) Devices

Some semiconductor (solid-state) devices can be damaged easily by static electricity. Such components commonly are called Electrostatically Sensitive (ES) Devices. Examples of typical ES

devices are integrated circuits and some eld-effect transistors

and semiconductor “chip” components. The following techniques should be used to help reduce the incidence of component damage caused by static 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 to prevent potential shock reasons prior to applying power to the unit under test.

2. After removing an electrical assembly equipped with ES 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 ES devices.

4. Use only an anti-static type solder removal device. Some solder

removal devices not classied as “anti-static” can generate electrical charges sufcient to damage ES devices.

5. Do not use freon-propelled chemicals. These can generate

electrical charges sufcient to damage ES devices.

6. Do not remove a replacement ES device from its protective package until immediately before you are ready to install it. (Most replacement ES 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 ES 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 handling unpackaged replacement ES devices. (Otherwise harmless motion such as the brushing together of your clothes fabric or the lifting of your

foot from a carpeted oor can generate static electricity sufcient to damage an ES device.)

General Soldering Guidelines

1. Use a grounded-tip, low-wattage soldering iron and appropriate tip size and shape that will maintain tip temperature within the range or 500 °F to 600 °F.

2. Use an appropriate gauge of RMA resin-core solder composed of 60 parts tin/40 parts lead.

3. Keep the soldering iron tip clean and well tinned.

4. Thoroughly clean the surfaces to be soldered. Use a mall wirebristle (0.5 inch, or 1.25 cm) brush with a metal handle. Do not use freon-propelled spray-on cleaners.

5. Use the following unsoldering technique

a. Allow the soldering iron tip to reach normal temperature.

(500 °F to 600 °F) b. Heat the component lead until the solder melts. c. Quickly draw the melted solder with an anti-static, suction-

type solder removal device or with solder braid.

CAUTION: Work quickly to avoid overheating the circuit

board printed foil.

6. Use the following soldering technique. a. Allow the soldering iron tip to reach a normal temperature

(500 °F to 600 °F)

b. First, hold the soldering iron tip and solder the strand against

the component lead until the solder melts.

c. Quickly move the soldering iron tip to the junction of the

component lead and the printed circuit foil, and hold it there only until the solder ows onto and around both the component lead and the foil. CAUTION: Work quickly to avoid overheating the circuit board printed foil.

d. Closely inspect the solder area and remove any excess or

splashed solder with a small wire-bristle brush.

- 4 -

IC Remove/Replacement

Some chassis circuit boards have slotted holes (oblong) through which the IC leads are inserted and then bent at against the circuit foil. When holes are the slotted type, the following technique should be used to remove and replace the IC. When working with boards using the familiar round hole, use the standard technique as outlined in paragraphs 5 and 6 above.

Removal

1. Desolder and straighten each IC lead in one operation by gently prying up on the lead with the soldering iron tip as the solder melts.

2. Draw away the melted solder with an anti-static suction-type solder removal device (or with solder braid) before removing the IC.

Replacement

1. Carefully insert the replacement IC in the circuit board.

2. Carefully bend each IC lead against the circuit foil pad and solder it.

3. Clean the soldered areas with a small wire-bristle brush. (It is not necessary to reapply acrylic coating to the areas).

"Small-Signal" Discrete Transistor Removal/Replacement

1. Remove the defective transistor by clipping its leads as close as possible to the component body.

2. Bend into a "U" shape the end of each of three leads remaining on the circuit board.

3. Bend into a "U" shape the replacement transistor leads.

4. Connect the replacement transistor leads to the corresponding leads extending from the circuit board and crimp the "U" with long nose pliers to insure metal to metal contact then solder each connection.

Power Output, Transistor Device Removal/Replacement

1. Heat and remove all solder from around the transistor leads.

2. Remove the heat sink mounting screw (if so equipped).

3. Carefully remove the transistor from the heat sink of the circuit board.

4. Insert new transistor in the circuit board.

5. Solder each transistor lead, and clip off excess lead.

6. Replace heat sink.

Diode Removal/Replacement

1. Remove defective diode by clipping its leads as close as possible to diode body.

2. Bend the two remaining leads perpendicular y to the circuit board.

3. Observing diode polarity, wrap each lead of the new diode around the corresponding lead on the circuit board.

4. Securely crimp each connection and solder it.

5. Inspect (on the circuit board copper side) the solder joints of the two "original" leads. If they are not shiny, reheat them and if necessary, apply additional solder.

3. Solder the connections. CAUTION: Maintain original spacing between the replaced component and adjacent components and the circuit board to prevent excessive component temperatures.

Circuit Board Foil Repair

Excessive heat applied to the copper foil of any printed circuit board will weaken the adhesive that bonds the foil to the circuit board causing the foil to separate from or "lift-off" the board. The following guidelines and procedures should be followed whenever this condition is encountered.

At IC Connections

To repair a defective copper pattern at IC connections use the following procedure to install a jumper wire on the copper pattern side of the circuit board. (Use this technique only on IC connections).

1. Carefully remove the damaged copper pattern with a sharp knife. (Remove only as much copper as absolutely necessary).

2. carefully scratch away the solder resist and acrylic coating (if used) from the end of the remaining copper pattern.

3. Bend a small "U" in one end of a small gauge jumper wire and carefully crimp it around the IC pin. Solder the IC connection.

4. Route the jumper wire along the path of the out-away copper pattern and let it overlap the previously scraped end of the good copper pattern. Solder the overlapped area and clip off any excess jumper wire.

At Other Connections

Use the following technique to repair the defective copper pattern at connections other than IC Pins. This technique involves the installation of a jumper wire on the component side of the circuit board.

1. Remove the defective copper pattern with a sharp knife. Remove at least 1/4 inch of copper, to ensure that a hazardous condition will not exist if the jumper wire opens.

2. Trace along the copper pattern from both sides of the pattern break and locate the nearest component that is directly connected to the affected copper pattern.

3. Connect insulated 20-gauge jumper wire from the lead of the nearest component on one side of the pattern break to the lead of the nearest component on the other side. Carefully crimp and solder the connections. CAUTION: Be sure the insulated jumper wire is dressed so the it does not touch components or sharp edges.

Fuse and Conventional Resistor Removal/Replacement

1. Clip each fuse or resistor lead at top of the circuit board hollow stake.

2. Securely crimp the leads of replacement component around notch at stake top.

- 5 -

SPECIFICATION

NOTE : Specifications and others are subject to change without notice for improvement

1. Application range

This specification is applied to the LED TV used LA75M chassis.

2. Test condition

Each part is tested as below without special appointment. (1) Temperature: 25 °C ± 5 °C, CST: 40 °C ± 2 °C (2) Relative Humidity: 65 % ± 10 % (3) Power Voltage

: Standard input voltage (AC 100-240 V~, 50/60 Hz) * Standard Voltage of each products is marked by models.

(4) Specification and performance of each parts are followed

each drawing and specification by part number in accordance with BOM.

(5) The receiver must be operated for about 5 minutes prior to

the adjustment.

3. Test method

(1) Performance: LGE TV test method followed (2) Demanded other specification

- Safety : CE, IEC specification

- EMC : CE, IEC

4. General Specification

No Item Specication Remark

1 Market North America

2 Receiving system ATSC / NTSC-M, 64 & 256 QAM

3 Available Channel VHF : 02~13

UHF : 14~69

DTV : 02-69

CATV : 01~135

CADTV : 01~135

4 Input Voltage AC 100 ~ 240V@ 50/60Hz AC 120V, 50/60Hz on the label (USA)

5 Aspect Ratio 16:9

6 Tuning System FS Rear gender(1EA)

7 Operating Environment 1) Temp : 0 ~ 40 deg

2) Humidity : ~ 80 %

8 Storage Environment 1) Temp. : -20 ~ 60 deg

2) Humidity : ~ 85%

- 6 -

5. External Input Support Format

5.1. Component 2D input(Y, CB/PB)

No. Resolution H-freq(kHz) V-freq.(kHz) Pixel clock(MHz) Proposed

1 720*480 15.73 59.94 13.50 SDTV ,DVD 480I

2 720*480 15.75 60.00 13.5135 SDTV ,DVD 480I

3 720*480 31.47 59.94 27.00 SDTV 480P

4 720*480 31.50 60.00 27.027 SDTV 480P

5 1280*720 44.96 59.94 74.176 HDTV 720P

6 1280*720 45.00 60.00 74.25 HDTV 720P

7 1920*1080 33.72 59.94 74.176 HDTV 1080I

8 1920*1080 33.75 60.00 74.25 HDTV 1080I

9 1920*1080 67.432 59.94 148.352 HDTV 1080P

10 1920*1080 67.50 60.00 148.50 HDTV 1080P

5.2. HDMI Input (PC/DTV)

No. Resolution H-freq(kHz) V-freq.(kHz) Pixel clock(MHz) Proposed Remark

HDMI-PC DDC

1 640*350 @70Hz 31.46 70.09 25.17 EGA X

2 720*400 @70Hz 31.46 70.08 28.32 DOS O

3 640*480 @60Hz 31.46 59.94 25.17 VESA(VGA) O

4 800*600 @60Hz 37.87 60.31 40.00 VESA(SVGA) O

5 1024*768 @60Hz 48.36 60.00 65.00 VESA(XGA) O

6 1152*864 @60Hz 54.34 60.05 80.002 VESA O

7 1280*1024 @60Hz 63.98 60.02 108.0 VESA (SXGA) O FHD only

8 1360*768 @60Hz 47.71 60.01 85.50 VESA (WXGA) O

9 1920*1080 @60Hz 67.5 60.00 148.5 WUXGA(CEA 861D) O FHD only

No. Resolution H-freq(kHz) V-freq.(kHz) Pixel clock(MHz) Proposed

DTV

1 640*480 31.46 59.94 25.125 SDTV 480P

2 640*480 31.50 60.00 25.125 SDTV 480P

5 720*480 31.47 59.94 27.00 SDTV 480P

6 720*480 31.50 60.00 27.027 SDTV 480P

7 1280*720 44.96 59.94 74.176 HDTV 720P

8 1280*720 45.00 60.00 74.25 HDTV 720P

9 1920*1080 33.72 59.94 74.176 HDTV 1080I

10 1920*1080 33.75 60.00 74.25 HDTV 1080I

11 1920*1080 26.97 23.97 74.176 HDTV 1080P

12 1920*1080 27.00 24.00 74.25 HDTV 1080P

13 1920*1080 33.71 29.97 74.176 HDTV 1080P

14 1920*1080 33.75 30.00 74.25 HDTV 1080P

15 1920*1080 67.43 59.94 148.352 HDTV 1080P

16 1920*1080 67.50 60.00 148.50 HDTV 1080P

- 7 -

SOFTWARE UPDATE

1. USB

(1) Insert the USB memory Stick to the USB port (2) Automatically detect the SW Version and show the below

message

(3) Click [YES]: initiate the download and install of the update.

2. NSU

(This Function is needed to connect to the internet)

(1) Menu -> All Settings -> General -> About This TV

(2) Click [CHEK FOR UPDATES] : system check newest

version

(4) Click [Check Now]: move to “About This TV” page for

update

(5) TV is updating

(6) After finished the update, below Pop-up appear

(7) Click [Yes] : TV will be DC OFF -> ON (8) After TV turned on, Check the updated SW Version and

Tool Option

(3) Click [DOWNLOAD AND INSTALL] (4) TV is updating

(5) After finished the update, below Pop-up appear

(6) Turn OFF the TV and On. Check the updated SW Version

and Tool Option

- 8 -

IC101

M2R

Audio AMP

(DTA-2010)

Digital Demod

DIF (+/-)

Sub Micom

(R5F100GEAFB)

IR / KEY

KEY

I2C

HDMI

MUX

LVDS

USB

SPDIF OUT

ETHERNET

USB1

USB2

OCP

1.5A

OCP

1.5A

HDMI1

HDMI2

(ARC)

REAR

OPTIC

LAN

51P(FHD)

DDR3 2133 4Gb x16

X_TAL

24MHz

WIFI Only

SUB

ASSY

USB_WIFI

DDR3 2133 4Gb x16

HDMI3

SIDE

CVBS/YPbPr

AV/COMP

REAR

EEPROM (256Kb)

eMMC 5.0 (4GB)

I2S

I2C

Analog Demod

1866

CVBS/SIF

X_TAL

32.768kHz

30P(HD)

BLOCK DIAGRAM

- 9 -

EXPLODED VIEW

200

400

800

540

521

120

820

LV1

530

900

121

500

570

571

AR1

700

A10

ARC1

IMPORTANT SAFETY NOTICE

Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in the EXPLODED VIEW. It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent Shock, Fire, or other Hazards. Do not modify the original design without permission of manufacturer.

- 10 -

DISASSEMBLY GUIDE

[Fig.1]

[Fig.2]

- 11 -

[Fig.3]

[Fig.4]

- 12 -

14 14

[Fig.5]

[Fig.6]

- 13 -

16 17

[Fig.7]

[Fig.8]

- 14 -

TROUBLE SHOOTING GUIDE

LGE Internal Use Only

Contents of Standard Repair Process

LGE Internal Use Only

No. Error symptom (High category) Error symptom (Mid category) Page Remarks

2 No video/No audio 2

3 Picture broken/ Freezing 3

4 Color error 4

9 Wrecked audio/discontinuation/noise 9

A. Video error

B. Power error

C. Audio error

No video/Normal audio 1

Vertical/Horizontal bar, residual image, light spot, external device color error

No power 6

Off when on, off while viewing, power

auto on/off

No audio/Normal video 8

Remote control & Local switch checking

MR15 operating checking 11

13 Camera operating checking 13

14 External device recognition error 14

15 E. Noise Circuit noise, mechanical noise 15

16 F. Exterior error Exterior defect 16

D. Function error

First of all, Check whether there is SVC Bulletin in GSCS System for these model.

Wifi operating checking 12

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