LG 43LJ55 -U Series User manual

P/NO : MFL69963002 (1703-REV01)
CHASSIS : LA75M
MODEL : 43LJ55** 43LJ55**-U*
LED TV
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only training and service purposes

- 2 -
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

- 3 -
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 MΩand 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
IMPORTANT SAFETY NOTICE
SAFETY PRECAUTIONS

- 4 -
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 explo-
sion 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 eas-
ily 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 dam-
age 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. Alter-
natively, obtain and wear a commercially available discharging
wrist strap device, which should be removed to prevent poten-
tial 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 expo-
sure 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 electri-
cally 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 replace-
ment 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 wire-
bristle (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 compo-
nent 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.

- 5 -
IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent at against the cir-
cuit 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 pos-
sible 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.
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.
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 connec-
tions).
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 con-
nected 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.

- 6 -
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%

- 7 -
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

- 8 -
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.
(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
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
(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

- 9 -
BLOCK DIAGRAM
IC101
M2R
Audio AMP
(DTA-2010)
Digital Demod
DIF (+/-)
Sub Micom (R5F100GEAFB)
IR / KEY
IR
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 I2C
I2C
Analog Demod
1866
CVBS/SIF
X_TAL
32.768kHz
30P(HD)

- 10 -
EXPLODED VIEW
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.
IMPORTANT SAFETY NOTICE
200
400
800 540 521
120
820
LV1
530
900
121
500
570
571
AR1
700
A10
ARC1

- 11 -
DISASSEMBLY GUIDE
[Fig.1]
[Fig.2]
3
1
3
2
2
333
4
5

- 12 -
BB
A
6
BB
A
6
6
66
6
88
88
8
8
8
8
8
88
88
77
[Fig.3]
[Fig.4]
6
6
6
8
9
9
88
88

- 13 -
10
12
11
13
14 14
15
[Fig.5]
[Fig.6]

- 14 -
16 17
18
19
20 20
[Fig.7]
[Fig.8]

TROUBLE SHOOTING GUIDE
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only

Contents of Standard Repair Process
No. Error symptom (High category) Error symptom (Mid category) Page Remarks
1
A. Video error
No video/Normal audio 1
2 No video/No audio 2
3 Picture broken/ Freezing 3
4 Color error 4
5 Vertical/Horizontal bar, residual image,
light spot, external device color error 5
6
B. Power error
No power 6
7 Off when on, off while viewing, power
auto on/off 7
8
C. Audio error
No audio/Normal video 8
9 Wrecked audio/discontinuation/noise 9
10
D. Function error
Remote control & Local switch checking 10
MR15 operating checking 11
11
12 Wifi operating checking 12
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
First of all, Check whether there is SVC Bulletin in GSCS System for these model.
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only

Normal
audio Y
N
Move to No
video/No audio
No video
Normal audio Check Back Light
On with naked eye On Y
N
Check Power
Board 13V etc. Normal
voltage Y
N
Replace T-con/Main
Board or module
Repair Power
Board or parts
Check Power Board 13V output
Normal
voltage Y Replace Inverter
or module
N
Repair Power
Board or parts
End
Always check & record S/W Version and White
Balance value before replacing the Main Board Replace Main Board Re-enter White Balance value
※Precaution
Established
date
Standard Repair Process
Revised date 1/16
Error
symptom A. Video error
No video/ Normal audio
☞A18☞A1
☞A18
☞A4 & A2
First of all, Check whether all of cables between board is inserted properly or not.
(Main B/D↔ Power B/D, LVDS Cable, Speaker Cable, IR B/D Cable,,,)
1
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only

Normal
voltage?
Check various
voltages of Power
Board (13V…)
No Video/
No audio
Check and
replace
MAIN B/D
Y
Replace Power
Board and repair
parts
N End
Standard Repair Process
A. Video error
No video/ No audio
☞A18
Established
date
Revised date 2/16
Error
symptom
2
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only

A. Video error
Picture broken/ Freezing
Y
N
☞A3
N
Check RF Signal level
Normal
Signal?
Check RF Cable
Connection
1. Reconnection
Check
S/W Version
S/W Upgrade
Check whether other equipments have problem or not.
(By connecting RF Cable at other equipment)
→ DVD Player ,Set-Top-Box, Different maker TV etc
SVC
Bulletin?
Replace
Main B/D
Check
Tuner soldering
Normal
Picture?
Y
N
Y
Close
Y Close
. By using Digital signal level meter
. By using Diagnostics menu on OSD
( Setting→ Channels→ Channel Tuning→ Manual Tuning → Check the Signal )
- Signal strength (Normal : over 50%)
- Signal Quality (Normal: over 50%)
Normal
Picture? Y
Contact with signal distributor
or broadcaster (Cable or Air)
N
Normal
Picture?
Y
Close
N
☞A4
Standard Repair Process
Established
date
Revised date 3/16
Error
symptom
3
N
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only

Color
error?
Y
N
※Check
and replace
Link Cable
(LVDS) and
contact
condition
Y
N
Replace Main B/D
Color
error?
Check error
color input
mode
Check color by input
-External Input
-COMPONENT
-AV
-HDMI
Y
External device
/Cable
normal
External Input/
Component
error
Check
external
device and
cable
Y
External device
/Cable
normal
HDMI
error
Check external
device and
cable
Replace Main/T-con B/D
Replace Main/T-con B/D
N
N
A. Video error
Color error
☞A6
N
Y
End
Replace module
Request repair
for external
device/cable
Color
error?
Check Test pattern
☞A8
☞A7
Standard Repair Process
Established
date
Revised date 4/16
Error
symptom
4
Copyright © 2017 LG Electronics Inc. All rights reserved.
Only for training and service purposes
LGE Internal Use Only