LG 24LQ520S User manual

P/NO : MFL70446540 (2204-REV00)
CHASSIS :
MODEL :
CAUTION
BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
SERVICE MANUAL
Copyright © 2022 LG Electronics Inc. All rights reserved. Only training and service purposes.
Any reproduction, duplication, distribution (including by way of email, facsimile or other electronic means),
publication, modification, copying or transmission of this Service Manual is STRICTLY PROHIBITED unless you
have obtained the prior written consent of the LG Electronics entity from which you received this Service Manual.
The material covered by this prohibition includes, without limitation, any text, graphics or logos in this Service
Manual.
24LQ520S 24LQ520S-PU
24LQ520S-WU
LM22N
LED TV

- 2 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
CONTENTS
CONTENTS .............................................................................................. 2
SAFETY PRECAUTIONS ......................................................................... 3
SERVICING PRECAUTIONS.................................................................... 4
SPECIFICATION ....................................................................................... 6
SOFTWARE UPDATE............................................................................... 9
BLOCK DIAGRAM.................................................................................. 10
EXPLODED VIEW .................................................................................. 11
TROUBLE SHOOTING GUIDE................................................. APPENDIX

- 3 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
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 1W), keep the resistor 10mm 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 1MΩand 5.2MΩ.
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 1.5K/10watt resistor in parallel with a 0.15uF 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
0.5mA.
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
1.5 Kohm/10W
0.15µF
To Instrument's
exposed
METALLIC PARTS
Good Earth Ground
such as WATER PIPE,
CONDUIT etc.
AC Volt-meter
When 25A is impressed between Earth and 2nd Ground
for 1 second, Resistance must be less than 0.1
*Base on Adjustment standard
IMPORTANT SAFETY NOTICE
SAFETY PRECAUTIONS

- 4 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
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 conflict 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
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 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 flammable mixture.
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 with this receiver only the test fixtures specified in this
service manual.
CAUTION: Do not connect the test fixture 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 field-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 classified as "anti-static" can generate
electrical charges sufficient to damage ES devices.
5. Do not use freon-propelled chemicals. These can generate
electrical charges sufficient 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 floor can generate static electricity
sufficient 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 1.25cm) 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 flows 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.
SERVICING PRECAUTIONS

- 5 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat 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.
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
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.

- 6 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
SPECIFICATION
NOTE : Specications and others are subject to change without notice for improvement.
1. Application Range
This spec sheet is applied to the LM22N chassis.
2. Specication
Each part is tested as below without special notice.
1) Temperature : 25 ˚C ± 5 ˚C (77 ˚F ± 9 ˚F),
CST : 40 ˚C ± 2 ˚C
2) Relative Humidity : 65 % ± 10 %
3) Power Voltage : Standard input voltage
(120 V ~, 50 / 60 Hz)
· Standard Voltage of each products is marked by models
4) Specication and performance of each parts are followed
each drawing and specication by part number in accord-
ance with BOM.
5) The receiver must be operated for about 20 minutes prior to
the adjustment.
3.Test method
1) Performance : LGE TV test method followed
2) Demanded other specication
- Safety : CE,IEC specication
- EMC : CE,IEC specication
No Item Specication Remarks
1 Market Korea / North America
2 Broadcasting system ATSC / NTSC-M, 64 & 256 QAM North America
ATSC / NTSC-M, ATSC3.0 Korea
3 Available Channel VHF 2 ~ 13 North America
UHF 14 ~ 69
DTV 2 ~ 69
CATV 1 ~ 135
CADTV 1 ~ 135
VHF 2 ~ 13 Korea
UHF 14 ~ 69
DTV 2 ~ 69
CATV 1 ~ 158
CADTV 1 ~ 158
UHDTV 2 ~ 56
UHDTV Cable 1 ~ 158
4 Receiving system Digital : ATSC, 64 & 256 QAM for North America model
Analog : NTSC-M
Digital : ATSC, ATSC3.0(UHD) for Korea model
Analog : NTSC-M
5 HDMI Input HDMI 1 PC / DTV Format Support 6Gbps
HDMI 2 PC / DTV Format Support 6Gbps, Support ARC
6 Audio out SPDIF Optical Audio out Vertical Refer 5. Feature and Func-
tion
7 USB Input EMF, DivX HD, For
SVC (download)
JPEG, MP3,
DivX HD
Refer 5. Feature and Func-
tion
4. Electrical Specication

- 7 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
No Item Specication Remarks
1 RF Input 1 Analog : NTSC-M for USA/Canada/Mexico
Digital : ATSC
2 Analog : NTSC-M, Digital : ATSC for KOREA
Digital : ATSC, ATSC3.0
2 HDMI Input 2 Digital Input Rear(2EA) depend on the model
3 Audio Output SPDIF 1 SPDIF out Rear(1EA) depend on the model
4 USB 1 EMF, DivX HD, For SVC (download) Side(1EA) depend on the model
5 Remote control Wireless Remote Control
6 Remocon Code LG code
7 Local Key One Key(Power On/O󰀨)
8 Set Installation Wall Mount / Desk top
5. Feature and Function

- 8 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
6. External Input Format
6.1. HDMI
6.1.1. DTV mode
No Resolution H-freq(kHz) V-freq(Hz) Pixel clock(MHz) Proposed
1 640*480 31.46 59.94 25.12 SDTV 480P
2 640*480 31.5 60 25.12 SDTV 480P
3 720*480 31.46 59.94 27 SDTV 480P
4 720*480 31.5 60 27.02 SDTV 480P
5 720*576 31.25 50 27 SDTV 576P
6 1280*720 44.95 59.94 74.17 HDTV 720P
7 1280*720 45 60 74.25 HDTV 720P
8 1280*720 37.5 50 74.25 HDTV 720P
9 1920*1080 28.12 50 74.25 HDTV 1080I
10 1920*1080 33.71 59.94 74.17 HDTV 1080I
11 1920*1080 33.75 60 74.25 HDTV 1080I
12 1920*1080 26.97 23.97 63.29 HDTV 1080P
13 1920*1080 27 24 63.36 HDTV 1080P
14 1920*1080 28.12 25 74.25 HDTV 1080P
15 1920*1080 33.71 29.97 79.12 HDTV 1080P
16 1920*1080 33.75 30 79.2 HDTV 1080P
17 1920*1080 56.25 50 148.5 HDTV 1080P
18 1920*1080 67.43 59.94 148.35 HDTV 1080P
19 1920*1080 67.5 60 148.5 HDTV 1080P
6.2.2. PC mode
No Resolution H-freq(kHz) V-freq(Hz) Pixel clock(MHz) Proposed Remarks
1 640*350 31.46 70.09 25.17 EGA
2 720*400 31.46 70.08 28.32 DOS
3 640*480 31.46 59.94 25.17 VESA(VGA)
4 800*600 37.87 60.31 40 VESA(SVGA)
5 1024*768 48.36 60 65 VESA(XGA)
6 1360*768 47.71 60.01 84.75 VESA(WXGA)
7 1152*864 54.34 60.05 80 VESA
8 1280*1024 63.98 60.02 109 SXGA FHD, UHD, 8K only
9 1920*1080 67.5 60 158.4 WUXGA(Reduced Blanking)

- 9 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
SOFTWARE UPDATE
1. USB Download
(option, Service only)
1) Put the USB Stick to the USB socket.
2) Automatically detecting update le in USB Stick.
- If your downloaded program version in USB Stick is Low,
it didn’t work. But your downloaded version is High, USB
data is automatically detecting. (Download Version High &
Power only mode, Set is automatically Download)
3) Show the message “Status: emmc copy”
4) Updating is starting.
5) Updating Completed, The TV will restart automatically.
Note: A message, ‘Updating Completed’ is not displayed on
the screen. When a SW Updating is nished(100%), a TV
SET automatically executes DC OFF/ON at the moment.
6) If your TV is turned on, check your updated version and
Tool option. (Explain the `, next stage)
* If downloading version is more high than your TV have, TV
can lost all channel data. In this case, you have to channel
recover. If all channel data is cleared, you didn’t have a DTV/
ATV test on production line.
* After downloading, have to adjust TOOL OPTION again.
1) Push "ADJ" key in service remote controller.
2) Select "Tool Option 1" and Push “OK” button
3) Punch in the number. (Each model has their number.)

- 10 - Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
BLOCK DIAGRAM
Main IC
eMMC (8GB)
CI Slot
USB1 (2.0)
OCP
HDMI2(ARC) HDMI1(2.0)
Air/ Cable
TUNER
(T2/C/A)
TUNER
(S,S2)
DVB-S
LNB
T2/C/S/S2 H-NIM tuner
IF (+/-)
P_TS_OUT
P_TS_IN
MICOM
IR / KEY
USB_WIFI
X_TAL
27MHz
Sub Assy
LAN
ETHERNET
SPDIF SPDIF OUT
MAIN Audio AMP I2S Out
I2C 0
LVDS
IF_S
IF
NVRAM (256Kb)
I2C_5
I2C 1/2
IQ (+/-), IP(+/-)
TS
LVDS FHD, HD 30P
USB_WIFI
1.2V
DDR
0.95V
Core
3.3V
Normal
1.0V
CPU
3.5V
ST_B
Y
1.8V
5V
Normal
0.96V 1.5V 3.3V 5V
1V 1.8V 3.5V_ST
0.95V 1.2V
3.3V
19V
3.3V
5V
5V
1V
1.8V
1.8V
3.5V_ST
3.5V_ST
3.3V
3.5V_ST
3.5V_ST
19V 3.5V_ST 19V
19V
19V
3.3V 13V
13V 3.3V
To Panel
Signal flow
Supplied Voltage
In/output Voltage
To WIFI/BT
Combo
eMMC
CLK/DATA/STRB
48bit
DDR4 2400 x16
(512MB X 3EA)
I2C 2
2.5V
VPP
2.5V
3.5V_ST
2.5V
A d a p t o r
V out
LED
To LED

Copyright © LG Electronics Inc. All rights reserved.
Only training and service purposes.
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
541
570
300 400
800
LV1AR1
ARC1
720 730
700
831
120
or
510
832
900
540
HW1
HB1
HC1
HS1

TROUBLE SHOOTING GUIDE
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

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
5Vertical/Horizontal bar, residual image,
light spot, external device color error 5
6B. Power error No power 6
7Off when on, off while viewing,
power auto on/off 7,8
8C. Audio error No audio/Normal video 9
9 Wrecked audio/discontinuation/noise 10
10
D. Function error
Remote control & Local switch checking 11
11 MR22x operating checking 12
12 WIFI operating checking 13
13 External device recognition error 14
14 E. Noise Circuit noise, mechanical noise 15
15 F. Exterior error Exterior defect 16
First of all, Check whether there is SVC Bulletin in GSCS System for these model.
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

Established
date
Revised date
Error
symptom A. Video error
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 Adaptor
19V etc. Normal
voltage Y
N
Replace T-con/Main
Board or module
Repair Adaptor or
parts
Check Adaptor 19V output
Normal
voltage
YReplace Module
N
Repair Adaptor
or parts
End
Always check & record S/W Version and White
Balance value before replacing the Main Board Replace Adaptor Re-enter White Balance value
※Precaution
No video / Normal audio
☞A9
☞A1
☞A9
☞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/WIFI Cable etc.)
1
Standard Repair Process
1/16
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

Established
date
Revised date
Error
symptom A. Video error
Normal
voltage?
Check various
voltages of Adaptor
(19V…)
No video /
No audio Check and
replace
MAIN B/D
Y
Replace Adaptor
and repair parts
NEnd
Standard Repair Process
No video / No audio
☞A9
2
2/16
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

Picture broken / Freezing
Y
N
☞A3
N
Check RF Signal level
Normal
Signal?
Check RF Cable
Connection
1. Reconnection
2. Install Booster
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
Normal
Picture?
Y
N
Y
Close
Y
. By using Digital signal level meter
. By using Diagnostics menu on OSD
( All Settings → General → Programmes → Programme Tuning & Settings → Signal Test )
- 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
Check Tuner
soldering Close
A. Video error
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

Color
error?
Y
N
※Check and
replace Link
Cable
(LVDS Cable)
and contact
condition
Y
N
Replace Main B/D
Color
error?
Check error
color input
mode
Check color by input
- External Input
- 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
☞A19
☞A7
Standard Repair Process
Established
date
Revised date 4/16
Error
symptom
4
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

Screen
normal?
N
YCheck
external
device
connection
condition
Y
N
Check and
replace Link
Cable
Normal?
Y
N
Screen
normal? Replace Main/T-con B/D
Replace
module
Check color condition by input
- External Input
- HDMI
End
Vertical/Horizontal bar, residual image, light spot
Request repair
for external
device
Vertical / Horizontal bar, residual image,
light spot, external device color error
External device screen error-Color error
External
Input,
HDMI
error
Connect other external
device and cable
(Check normal operation of
External Input, HDMI by
connecting Jig, pattern
Generator ,Set-top Box etc. N
Y
Replace
Main/T-con
B/D
Screen
normal?
Check screen
condition by input
-External Input
-HDMI
Request repair for
external device
Check S/W Version
Y
N
Check
version
S/W Upgrade
Y
N
Normal
screen?
End
Y
N
Replace Main B/D
For with T-con panel
Replace
Module
Screen
normal?
End
Established
date
Revised date 5/16
Error
symptom
Standard Repair Process
☞A6 ☞A7
Check Test pattern
5
For other panel
☞A19
A. Video error
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

No power
Power
LED On? Y
N
DC Power on
by pressing Power Key
On Remote control
Y
N
Normal
operation? Check Power
On ‘”High”
Check Power cord
was inserted properly
Check LED Replace
Adaptor
Measure voltage of each
output of Power B/D
N
Y
Normal
voltage? Replace Main B/D
Y
OK?
Replace Main B/D
N
Y
Normal?
Check ST-BY 7.8V
Replace Adaptor
N
Y
Normal
voltage?
Replace Adaptor
Y
☞A8
☞A9
☞A9
☞A9
Standard Repair Process
Established
date
Revised date 6/16
Error
symptom
6
- Stand-By : Red or Turn On
- Operating : Turn Off
Close
B. Power error
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.

B. Power error
Off when on, off while viewing, power auto on/off
Error? N
Y
Check Power Off
Mode
Fix A/C cord & Outlet
and check out
Check A/C cord, Outlet Replace Main B/D
CPU
Abnormal
(If Power Off mode is
not displayed)
Check Adaptor
voltage
Y
N
Replace Main B/D
Normal
voltage?
Replace Adaptor
Replace Adaptor
N
Y
Normal? End
※Caution
Check and fix exterior
of Power B/D Part
☞A10
☞A10
Established
date
Revised date 7/16
Error
symptom
Standard Repair Process
7
Abnormal
1
Copyright ⓒ2022 LG Electronics Inc. All rights reserved.
Only training and service purposes.