LG 42LH90 Series User manual

42LH90
42LH90
LED Backlights
1080P
Direct View LCD
Training
Original February 09, 2010
Updated July 28, 2010

LCD DV 42LH90
2February 2010
OUTLINE
OUTLINE
• Main Board
• Switch Mode Power Supply
Preliminary Section:
Troubleshooting Section: Board Operation Troubleshooting of :
Contact Information, Preliminary Matters, Specifications,
LCD Overview, General Troubleshooting Steps,
Signal Distribution, Disassembly Instructions and Voltages
• Ft Control Board
• T-CON (TFT Controller) Panel Driver board
•Side Keys
•Inverter Board (LED Backlight Driver)
•Speakers
Disassembly Section: Removal of Circuit Boards

LCD DV 42LH90
3February 2010
42LH90 LCD Direct View Display
Section 1
This Section will cover Contact Information and remind the Technician of Important Safety Precautions for
the Customers Safety as well as the Technician and the Equipment.
Basic Troubleshooting Techniques which can save time and money sometimes can be overlooked. These
techniques will also be presented.
This Section will get the Technician familiar with the Disassembly, Identification and Layout of the LCD
Display Panel.
At the end of this Section the Technician should be able to Identify the Circuit Boards and have the ability
and knowledge necessary to safely remove and replace any Circuit Board or Assembly.
Overview of Topics to be Discussed
Overview of Topics to be Discussed

LCD DV 42LH90
4February 2010
IMPORTANT SAFETY NOTICE
IMPORTANT SAFETY NOTICE
The information in this training manual is intended for use by persons possessing an adequate background in
electrical equipment, electronic devices, and mechanical systems. In any attempt to repair a major Product,
personal injury and property damage can result. The manufacturer or seller maintains no liability for the
interpretation of this information, nor can it assume any liability in conjunction with its use. When servicing this
product, under no circumstances should the original design be modified or altered without permission from LG
Electronics. Unauthorized modifications will not only void the warranty, but may lead to property damage or
user injury. If wires, screws, clips, straps, nuts, or washers used to complete a ground path are removed for
service, they must be returned to their original positions and properly fastened.
CAUTION
CAUTION
To avoid personal injury, disconnect the power before servicing this product. If electrical power is required for
diagnosis or test purposes, disconnect the power immediately after performing the necessary checks. Also be
aware that many household products present a weight hazard. At least two people should be involved in the
installation or servicing of such devices. Failure to consider the weight of an product could result in physical
injury.
Preliminary Matters (The Fine Print)
Preliminary Matters (The Fine Print)

LCD DV 42LH90
5February 2010
Today’s sophisticated electronics are electrostatic discharge (ESD) sensitive. ESD can weaken or damage
the electronics in a manner that renders them inoperative or reduces the time until their next failure.
Connect an ESD wrist strap to a ground connection point or unpainted metal in the product. Alternatively,
you can touch your finger repeatedly to a ground connection point or unpainted metal in the product. Before
removing a replacement part from its package, touch the anti-static bag to a ground connection point or
unpainted metal in the product. Handle the electronic control assembly by its edges only. When
repackaging a failed electronic control assembly in an anti-static bag, observe these same precautions.
Regulatory Information
Regulatory Information
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to
Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful
interference when the equipment is operated in a residential installation. This equipment generates, uses,
and can radiate radio frequency energy, and, if not installed and used in accordance with the instruction
manual, may cause harmful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning the equipment off and on, the user is
encouraged to try to correct the interference by one or more of the following measures: Reorient or relocate
the receiving antenna; Increase the separation between the equipment and the receiver; Connect the
equipment to an outlet on a different circuit than that to which the receiver is connected; or consult the
dealer or an experienced radio/TV technician for help.
ESD Notice
ESD Notice
(Electrostatic Static Discharge)
(Electrostatic Static Discharge)

LCD DV 42LH90
6February 2010
Customer Service (and Part Sales) [phone]
Technical Support (and Part Sales) [phone]
USA Website (GSFS) http://gsfs-america.lge.com
Customer Service Website us.lgservice.com
LG Web Training lge.webex.com
LG CS Academy lgcsacademy.com
Published February 2010 by LG Technical Support and Training
LG Electronics Alabama, Inc.
201 James Record Road, Huntsville, AL, 35813.
32LG40, 32LH30, 37LH55, 42LG60, 42LG70, 42LH20, 42LH40, 42LH50, 42LH90, 42SL80,
47LG90, 47LH85, 47LE8500
42PG20, 42PQ20, 42PQ30, 50PG20, 50PJ350, 50PK750, 50PS80, 50PS60, 60PK750,
60PS11, 60PS60, 60PS80
LCD-DV:
PLASMA:
Also available on the Plasma Page:
PDP Panel Alignment Handbook, Schematics with Bookmarks
Plasma Control Board ROM Update (Jig required)
LG Contact Information
LG Contact Information
Presentations with Audio/Video
and Screen Marks
New Training Materials on
New Training Materials on
the Learning Academy site
the Learning Academy site
http://136.166.4.200

LCD DV 42LH90
7February 2010
Safety and Handling Regulations
1. Approximately 20 minute pre-run time is required before making any picture performance
adjustments from the Menu.
2. Refer to the Voltage/Current silk screening on the Switch Mode Power Supply.
3. C-MOS circuits are sensitive to static electricity.
Use caution when dealing with these IC and circuits.
4. Exercise care when making voltage and waveform checks to prevent costly short circuits
from damaging the unit.
5. Be cautious of lost screws and other metal objects to prevent a possible short in the
circuitry.
1. Check the appearance of the Replacement Panel and Circuit Boards for both physical
damage and part number accuracy.
2. Check the model label. Verify model names and board model matches.
3. Check details of defective condition and history. Example: Oscillator failure dead set, etc…
Checking Points to be Considered
LCD Direct View Overview
LCD Direct View Overview

LCD DV 42LH90
8February 2010
Basic Troubleshooting Steps
Basic Troubleshooting Steps
Define, Localize, Isolate and Correct
•Define Look at the symptom carefully and determine what circuits could be causing
the failure. Use your senses Sight, Smell, Touch and Hearing. Look for burned parts and
check for possible overheated components. Capacitors will sometimes leak dielectric material
and give off a distinct odor. Frequency of power supplies will change with the load, or listen for
relay closing etc. Observation of the front Power LED may give some clues.
•Localize After carefully checking the symptom and determining the circuits to be
checked and after giving a thorough examination using your senses the first check should
always be the DC Supply Voltages to those circuits under test. Always confirm the supplies
are not only the proper level but be sure they are noise free. If the supplies are missing check
the resistance for possible short circuits.
•Isolate To further isolate the failure, check for the proper waveforms with the
Oscilloscope to make a final determination of the failure. Look for correct Amplitude Phasing
and Timing of the signals also check for the proper Duty Cycle of the signals. Sometimes
“glitches” or “road bumps” will be an indication of an imminent failure.
•Correct The final step is to correct the problem. Be careful of ESD and make sure to
check the DC Supplies for proper levels. Make all necessary adjustments and lastly always
perform a Safety AC Leakage Test before returning the product back to the Customer.

LCD DV 42LH90
9February 2010
This section of the manual will discuss the specifications of the
42LH90
LCD Direct View Display
42LH90 PRODUCT INFORMATION SECTION
42LH90 PRODUCT INFORMATION SECTION

LCD DV 42LH90
10 February 2010
Basic Specifications
Basic Specifications
Key TV Features
•LED Backlight with Local Dimming
•TruMotion 240Hz
•Intelligent Sensor
•Full HD 1080p
•2,000,000:1 Contrast Ratio
•2.4ms Response Time
•500 cd/m² Brightness
•Wide Color gamut
•Super IPS Panel
•XD Engine
•24fps Real Cinema
•ISFccc Ready
•Picture Wizard
•AV Mode II (Cinema, Sports, Game)
•NTSC / ATSC / Clear QAM
•Audio Output Power 10W x 2
•Invisible Speaker system
•Clear Voice II
•SRS TruSurround XT™
•Smart Volume Controller
•Dolby® Digital 5.1 Decoder
•Backlight Control
•Video Mute
•ENERGY STAR® 3.0 Compliant
•4 HDMI™ v1.3 with Deep Color
•SIMPLINK™ Connectivity
•2 HD Component Video Inputs
•2 Composite inputs
•1 Digital Audio Out
•USB 2.0 (JPEG, MP3, MP4, Divx)
•PC Connectivity (D-Sub 15pin)
•RF Antenna Input

LCD DV 42LH90
11 February 2010
Basic Specifications (LOGO Familiarization)
Basic Specifications (LOGO Familiarization)
Full HD 1080p Resolution
Displays HDTV programs in full 1920 x 1080p resolution for a more detailed picture.

LCD DV 42LH90
12 February 2010
TOP PORTION BOTTOM PORTION
Remote Control Familiarization
Remote Control Familiarization
p/n MKJ61841701

LCD DV 42LH90
13 February 2010
Accessing the Service Menu
Accessing the Service Menu
To access the Service Menu.
1) You must have the Service
Remote. p/n 105-201M
2) Press “In-Start”
3) A Password screen appears.
Note: A Password is required
to enter the Service Menu.
Enter; 0000

LCD DV 42LH90
14 February 2010
TV Rear Input / Output Jacks
TV Rear Input / Output Jacks
Rear In/Out Jacks
USB Port
Software Upgrades
Music, Photos
Side In/Out
MAIN BOARD
Rear and Side
Input/Output locations

LCD DV 42LH90
15 February 2010
1) Create an LG_DTV folder on the USB Flash Drive
2) Copy new software (xxx.epk) to "LG_DTV"
folder. Make sure to have correct software file.
3) With TV turned on, insert USB flash drive.
4) You can see the message
“TV Software Upgrade” (See figure to right)
5) Cursor left and highlight "START" Button and
push “Enter” button using the remote control.
6) You can see the download progress Bar.
7) Do not unplug until unit has automatically
restarted.
8) When download is completed, you will see
“COMPLETE”.
9) Your TV will be restarted automatically.
Software Download
Software Download
Shows the
Currently
Installed
Version
Shows the
Software
Version
found on the
USB Flash
Drive
* CAUTION:
Do not remove AC power or the USB Flash Drive.
Do not turn off Power, during the upgrade
process.

42LH90 Dimensions
7-7/8"
200mm
28-3/16"
716.28mm
14-1/8"
357.98mm
42"
1066.8mm
Remove 4 screws to
remove stand for
wall mount
16-15/16"
430mm
17-7/8"
454mm
30-5/8"
777.88mm
Center 7-7/8"
200mm
9-5/8"
244mm
10-5/8"
270mm
2-7/16"
61.6mm
Weight without Stand: 43 lb
Weight with Stand: 51.1 lb
3-11/16"
93.98mm
14-3/16"
360.68mm
21"
533.4mm
14-1/8"
357.98mm
16
42LH90 Product Dimensions
42LH90 Product Dimensions
There must be at least 4 inches of Clearance on all sides
Wattage
Average 210W
Stand By <1W
Model No.
Serial No.
Label

LCD DV 42LH90
17 February 2010
DISASSEMBLY SECTION
DISASSEMBLY SECTION
Disassembly:
This section of the manual will discuss Disassembly, Layout
(Circuit Board Identification) of the 42LH90 LCD Direct View Television.
Upon completion of this section the Technician will have a better
understanding of the disassembly procedures, the layout of the printed
circuit boards and be able to identify each board.

LCD DV 42LH90
18 February 2010
Remove the 23 screws indicated.
Pay attention to the size and type of screw
as there are many different types.
Putting in an improper screw when
reassembling may Cause damage.
The Stand does not need to be removed before removing the back.
Removing the Back Cover
Removing the Back Cover
Bottom two screws do
not have to be
removed.
Decorative Plastic
Cap (if used) must
be removed.

LCD DV 42LH90
19 February 2010
Circuit Board Layout
Circuit Board Layout
POWER SUPPLY
Intelligent
Sensor / IR AC Input
Right LED
Connection
Rear Inputs
Power
Button
Main Board
Left LED
Connection
Tweeter R
Full Range
Speaker R
Tweeter L
Side Keys
Moving
LED
LVDS Cables
TFT Panel
EAJ60694101
p/n EAY58584001
p/n EBR62151101
p/n EAB58534501 p/n EAB58536001
T-CON board
p/n EAT60665101
Full Range
Speaker L
INVERTER
p/n EAY60702001
Side
Inputs
p/n EAD60679428
p/n EAD60679364

T-CON
POWER
SUPPLY MAIN
BOARD
INVERTER
CN306
P203
P201
SK100
SK101
CN1
CN3
CN4
CN307 N/C
CN305 N/C CN1 CN2
CN5 CN4
P3500 P3502
P3501
P700
P1200
P600
Speakers (Front Left)Speakers (Front Right)
AC In
Main
Power
IR
LED
KEY BOARD
P100
P101
IR
P100
P103
J1
42LH90 Connector Identification Diagram
42LH90 Connector Identification Diagram
P101N/C
LED
TFT PANEL
20