LG 28LM4 0B-PU Series User manual
312 MFL71428602 (1902-RE00)
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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.
- 2 -
&217(176
2019
CONTENTS .............................................................................................. 2
SAFETY PRECAUTIONS ........................................................................ 3
SERVICING PRECAUTIONS ................................................................... 4
SPECIFICATION ...................................................................................... 6
SOFTWARE UPDATE............................................................................... 8
BLOCK DIAGRAM ................................................................................. 11
EXPLODED VIEW .................................................................................. 12
DISASSEMBLE GUIDE........................................................................... 13
TROUBLE SHOOTING GUIDE ................................................................22
- 3 -
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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.
*HQHUDO*XLGDQFH
An LVRODWLRQ 7UDQVIRUPHU VKRXOG DOZD\V EH XVHG 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.
%HIRUHUHWXUQLQJWKHUHFHLYHUWRWKHFXVWRPHU
always perform an $& OHDNDJH FXUUHQW FKHFN on the
exposed
metallic parts of the cabinet, such as antennas, terminals, etc.,
to
be sure the set is safe to operate without damage of
electrical
shock.
/HDNDJH&XUUHQW&ROG&KHFN$QWHQQD&ROG&KHFN
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.
Another abnormality exists that must be corrected before
the
receiver is returned to the
customer.
/HDNDJH&XUUHQW+RW&KHFN(See below
Figure)
Plug the AC cord directly into the AC
outlet.
'RQRWXVHDOLQH,VRODWLRQ 7UDQVIRUPHU GXULQJ WKLV
FKHFN
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.
/HDNDJH&XUUHQW+RW&KHFNFLUFXLW
2019
- 4 -
6(59,&,1*35(&$87,216
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 precau-
tions. 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.
&$87,21: 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 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)
&$87,21: 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.
&$87,21: Do not connect the test fixture ground strap to any
heat sink in this receiver.
(OHFWURVWDWLFDOO\6HQVLWLYH(6'HYLFHV
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 field-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 discharg-
ing 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 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 sol-
der 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 elec-
trically 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 mate-
rial to the chassis or circuit assembly into which the device will
be installed.
&$87,21: Be sure no power is applied to the chassis or cir-
cuit, 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 floor can generate static electricity suf-
ficient to damage an ES device.)
General Soldering Guidelines
1. Use a grounded-tip, low-wattage soldering iron and appropri-
ate 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 flows onto and around both the compo-
nent lead and the foil.
&$87,21: 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.
2019
- 5 -
,&5HPRYH5HSODFHPHQW
Some chassis circuit boards have slotted holes (oblong) through
which the IC leads are inserted and then bent flat 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).
6PDOO6LJQDO'LVFUHWH7UDQVLVWRU
5HPRYDO5HSODFHPHQW
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 remain-
ing 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.
&LUFXLW%RDUG)RLO5HSDLU
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 when-
ever 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.
&$87,21: Be sure the insulated jumper wire is dressed so the
it does not touch components or sharp edges.
2019
- 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
MS3553T.PB791 chassis.
2. Requirement for Test
Each part is tested as below without special appointment.
1) Temperature: 25 °C ± 5 °C(77 °F ± 9 °F), CST: 40 °C ± 5 °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
NOM-001, NOM-032, NOM-192
-EMI：FCC-15/ICES-003/BETS-7 for NAFTA
- Energy: CEC/NRCan/QUEBEC/ONTARIO/British Columbia for
NAFTA
4. Model General Specification
No. Item Specification Remarks
1Receiving System NTSC-M, ATSC,
NTSC-M, ATSC, 64&256 QAM(USA Only)
2Promramme coverage 1) VHF : 02~13
2) UHF : 14~69
3) DTV : 02-69
4) CATV : US 01~135 ,
5) CADTV : US 01~135,
3Input Voltage AC 127V~, 60Hz for Mexico; 120V~, 60Hz for USA
4Screen Size 28 inch Wide (1366 × 768)
5Aspect Ratio 16:9
6Module LCM Model No. Panel Model No. Panel Resolution Frame Rate
BOEI280WX1 HV280WX2-270(A) BOE HD 60 Hz
7Component & Com-
posite Input Component + AV Bottom : CVBS(Y), Pb, Pr
Bottom : Audio L/R
8HDMI Input HDMI2 Side
HDMI1 bottom
9USB USB Side (USB 2.0)
10 Optical Optical Side
2019
- 7 -
&RPSRQHQW9LGHR,QSXW<&E3E &
U
3
U
No. Resolution H-fre
q(
kHz
)
V-fre
q
.
(
kHz
)
1 720*480i 15.73
60.00
2 720*480
p
31.50 60.00
3 1440*576i 16.63 50.00
4 720*576
p
31.50 50.00
5 1280*720
p
37.50 50.00
6 1280*720
p
45.00 60.00
7 1920*1080i 28.13 50.00
8 1920*1080i 33.75 60.00
9 1920*1080
p
56.25 50.00
10 1920*1080
p
67.50 60.00
+'0,,QSXW
No. Resolution H-freq(kHz) V-freq.(kHz)
3&'9,
1 720*400 31.469 70
2 640*480 31.469 59.940
3 800*600 35.156 56.250
4800*600 37.879 60.317
5 1024*768 48.363 60.004
6 1280*720 45.0 60
7 1280*768 47.776 59.870
8 1366*768 49.1 60
'79
1 640*480p 31.47 59.94
2 640*480p 31.5 60.00
3 720*480p 31.47 59.94
4 720*480p 31.5 60.00
5 1280*720p 44.96 59.94
6 1280*720p 45.00 60.00
7 720(1440)*480i 15.73 59.94
8 720(1440)*480i 15.75 60.00
9 720*576p 31.25 50.00
10 1280*720p 37.5 50.00
11 720(1440)*576i 15.63 50.00
12 1920*1080i 28.125 50.00
13 1920*1080i 33.72 59.94
14 1920*1080i 33.75 60.00
15 1920*1080p 26.97 23.976
16 1920*1080p 27.00 24.00
17 1920*1080p 33.716 29.976
18 1920*1080p 33.75 30.00
19 1920*1080p 56.25. 50.00
20 1920*1080p 67.432 59.94
21 1920*1080p 67.50 60.00
2019
- 8 -
SOFTWARE UPDATE PROCEDURE
0. Reasonwhyareacodeneedtosetwhenchangemainboard.
Area code is related with broadcast country setting of user menu.
If it is applied wrong number, customer can not see own country in broadcast country list when initial set.
Check Area code after change mainboard.
It should be match with selling country.
Example(Broadcast Country setting of user menu)
Refer to appendix for details.
2019
- 9 -
1. USBUpgrade
Checksoftwareupgradebinfilenameasbelow.OnlybinfilenameisthesameasTVset,USBupgrade
canbesuccess.
Region Model Software Name(FY2019)
Nafta 28 LM_NAF_3553.bin
NeeddoAConupgradeasbelowsteps.
1. CopythesoftwareBintotheUSBroot.
2. InserttheUSBtothemainboardUSBport.
3. ThenACon.
4. ThentheTVwillupgrade,andneedtorebootafterupgradesuccess.
Upgrading:
LEDindicatorblinkingred1000msgreen1000msalternate,TVwillturntoupgradesucceedorfailed
statusafterfinishupgrading.
Upgradesucceed:
LEDindicatorblinkingred250msgreen250msalternate.
Upgradefailed:
LEDindicatorblinkingred1750msgreen250msalternate.
PulloutUSBandpoweronTVafterupgradingfinish.
2019
- 10 -
2.AreaCodeSettingGuide
SETTING+1147Ͳ>FactorySettingsͲ>GENERALSETTINGͲ>AreaOption:
1.AreaCode:
~3:NAFTA
RegionAreaCodeSubsidiaryMainMarketSubMarket
NAFTA
1LGEUS
USAUSA
USAUSA
USAUSA
3LGECI
CanadaCanada
CanadaCanada
2LGEMS
MexicoMexico
MexicoMexico
MexicoMexico
Usercanselectareacodebyleftandrightkey,andsetareacodewithitem“5Set”byrightandOKkey.
2.LangGr.:English.
3.TeletextLangGr.:English.
4.CountryGroup:Displaythesubsidiary,suchLGEUS,LGECI,andsoon.
5.Set:Selecttheareacodeuserwant,andpressOKorRightkeytosetareacode,andthenTVwillrebootandthecountrywill
changetothecountrieshasselectedinareaoption.
2019
%/2&.',$*5$0
- 11 - 2019
22019
EXPLODED VIEW
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.
200
500
800
HW1
120
120 700
LV1
540 541
400
901
902
A10
AR1
542
- 13 -
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2019
- 14 -
2019
5HPRYHWKHEDFNFRYHU
- 15 -
2019
5HPRYHWKHSRZHUFRUGKRUQFRQQHFWLRQDQGUHPRYHERWKVLGHUDLOVRIWKHPDLQERDUG
- 16 - 2019
4.. Remove the screwVthat lock the main board after removing the mirror line and function key
line.
- 7 - 2019
5. Remove the tape and unplug the LVDS.
- 18 - 2019
6. Remove the tape that holds the speaker line and remove the horn.
- 19 -
2019
7. Remove the wall bracket.
- 20 -
2019
8.. Remove the tape thaW holds the IR plate line and remove the IR plate.
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