42lh20 presentation

7/30/2019 42LH20 Presentation

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42LH2042LH20Direct View LCD

Original: March 2009

Updated: February 11, 2010


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February 2009 42LH202

OUTLINEUTLINE

Main Board

T-CON Board

Circuit Board Operation, Troubleshooting of :

Switch mode Power Supply

Section 1

Section 2

Contact Information, Preliminary Matters, Specifications,LCD Overview, General Troubleshooting Steps,Signal Distribution, Disassembly Instructions and Voltages

Ft Control Board

Side Keys


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42LH20 LCD Direct View Display

Section 1

This Section will cover Contact Information and remind the Technician of Important Safety Precautions forthe Customers Safety as well as the Technician and the Equipment.

Basic Troubleshooting Techniques which can save time and money sometimes can be overlooked. Thesetechniques will also be presented.

This Section will get the Technician familiar with the Disassembly, Identification and Layout of the LCDDisplay Panel.

At the end of this Section the Technician should be able to Identify the Circuit Boards and have the abilityand knowledge necessary to safely remove and replace any Circuit Board or Assembly.

Overview of Topics to be Discussedverview of Topics to be D iscussed


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IMPORTANT SAFETY NOTICEMPORTANT SAFETY NOTICEThe 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 theinterpretation of this information, nor can it assume any liability in conjunction with its use. When servicing thisproduct, under no circumstances should the original design be modified or altered without permission from LGElectronics. Unauthorized modifications will not only void the warranty, but may lead to property damage oruser injury. If wires, screws, clips, straps, nuts, or washers used to complete a ground path are removed forservice, they must be returned to their original positions and properly fastened.

CAUTIONAUTIONTo avoid personal injury, disconnect the power before servicing this product. If electrical power is required fordiagnosis or test purposes, disconnect the power immediately after performing the necessary checks. Also beaware that many household products present a weight hazard. At least two people should be involved in theinstallation or servicing of such devices. Failure to consider the weight of an product could result in physicalinjury.

Preliminary Matters (The Fine Print)reliminary Matters (The Fine Print)


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Todays sophisticated electronics are electrostatic discharge (ESD) sensitive. ESD can weaken or damagethe 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. Beforeremoving a replacement part from its package, touch the anti-static bag to a ground connection point orunpainted 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 Informationegulatory InformationThis equipment has been tested and found to comply with the limits for a Class B digital device, pursuant toPart 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmfulinterference 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 instructionmanual, may cause harmful interference to radio communications. However, there is no guarantee thatinterference will not occur in a particular installation. If this equipment does cause harmful interference toradio or television reception, which can be determined by turning the equipment off and on, the user isencouraged to try to correct the interference by one or more of the following measures: Reorient or relocatethe receiving antenna; Increase the separation between the equipment and the receiver; Connect theequipment to an outlet on a different circuit than that to which the receiver is connected; or consult thedealer or an experienced radio/TV technician for help.

ESDSD Noticeotice (Electrostatic Static Discharge)(Electrostatic Static Discharge)


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LCD or PLASMA 2009 Model6

Contact Informationontact Information

Also available on theAlso available on the

Plasma pagePlasma page

New Training Materials onNew Training Materials on

the Learning Academy s itethe Learning Academy s ite

Customer Service (and Part Sales) (800) 243-0000

Technical Support (and Part Sales) (800) 847-7597

USA Website (GCSC) aic.lgservice.com

Customer Service Website us.lgservice.com

LG Web Training lge.webex.com

LG CS Academy lgcsacademy.com

LG Electronics Alabama, Inc. 201

James Record Road, Huntsvi lle,

AL, 35813.

http://136.166.4.200

Published March 2009 by LG Technical Support and Training

32LG40, 32LH30, 37LH55, 42LG60, 42LG70, 42LH20, 42LH40, 42LH50, 42LH90, 42SL80,

47LG90, 47LH85

42PG20, 42PQ20, 42PQ30, 50PG20, 50PS80, 50PS60, 60PS11

LCD-DV:

PLASMA:

Plasma Panel

Alignment Handbook

Presentationswith Audio/Video

and Screen Marks


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Safety and Handling Regulations

1. Approximately 20 minute pre-run time is required before any adjustments are performed.2. SMPS adjustments are factory sealed. They are VR301 (Frequency) and VR302 (Current)3. Be cautious of electric shock from the Backlight section, it uses high voltage AC. Check that

the Power Supply and Drive Circuits are completely discharged because of residual currentstored before Circuit Board removal.

4. C-MOS circuits are sensitive to static electricity.Use caution when dealing with these IC and circuits. Always handle the circuit boards on theoutside edges while using ESD protection.

5. Exercise care when making voltage and waveform checks to prevent costly short circuitsfrom damaging the unit.

6. Be cautious of loose screws and other metal objects to prevent a possible short in thecircuitry.

1. Check the appearance of the Replacement Panel and Circuit Boards for both physical damageand 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

Observe the following items

LCD Direct View OverviewCD Direct View Overview


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Basic Troubleshooting Stepsasic Troubleshooting StepsDefine, Localize, Isolate and Correct

Define Look at the symptom carefully and determine what circuits could be causingthe failure. Use your senses Sight, Smell, Touch and Hearing. Look for burned parts andcheck for possible overheated components. Capacitors will sometimes leak dielectric materialand 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 bechecked and after giving a thorough examination using your senses the first check shouldalways be the DC Supply Voltages to those circuits under test. Always confirm the suppliesare not only the proper level but be sure they are noise free. If the supplies are missing check

the Diode Check for possible short circuits.

Isolate To further isolate the failure, check for the proper waveforms with theOscilloscope to make a final determination of the failure. Look for correct Amplitude Phasingand Timing of the signals also check for the proper Duty Cycle of the signals. Sometimes

glitchesor road bumpswill be an indication of an imminent failure.

Correct The final step is to correct the problem. Be careful of ESD and make sure tocheck the DC Supplies for proper levels. Make all necessary adjustments and lastly alwaysperform a Safety AC Leakage Test before returning the product back to the Customer.


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This section of the manual will discuss the specifications of the 42LH20LCD Direct View Display Panel.

42LH20 Product Information2LH20 Product Information


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Basic Specificationsasic SpecificationsKey Features

42" Screen 720p HD Resolution Two (2) HDMI(TM) (V.1.3 with Deep Color) ISFccc Ready Smart Energy Saving LG SimpLink (TM) (32-inch and above) LG Core Technologies (32-inch and above) Dynamic Contrast Ratio 12,000:1 Response Time (G to G) 8ms Brightness 500 cd/m2 Viewing Angle 178 / 178 Life Span (Typical) 60,000 hr Built-in Tuner ATSC/NTSC/Clear QAM

HDMI/HDCP Input 2 v1.3

Cabinet Color Glossy Piano-Black Limited Warranty 1 Year Parts/Labor


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HD RESOLUTION 720p HD Resolut ion Pixels: 1365 (H) 768 (V)High definition television is the highest performance segment of theDTV system used in the US. Its a wide screen, high-resolution videoimage, coupled with multi-channel, compact-disc quality sound.

FORMATS480I

480P

1080I

720P

1080P

Interlaced

Progressive

Interlaced

Progressive

Progressive

Interlaced

2 Fields to make a Frame

Progressive

Each Field is a Fr ame

Think of sync as the Panels Refresh Rate

240 Lines

480 Lines

540 Lines

720 Lines

1080 Lines

NTSC

SD

HD

HD

HD

Possible Frame

Rates:

24FPS30FPS

60FPS

BASICPIXEL COUNTS

720P Panel1365 (H) 768 (V)

1080P Panel1920 (H) x 1080 (V)

Pixel Count Compared to Resolutionixel Count Compared to Resolution


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Basic Specifications (LOGO Familiarization) Page 1asic Specifications (LOGO Familiarization) Page 1

SIMPLINK

Allows for convenient control of other LG SimpLink products using theexisting HDMI connection.

Clear Voice TechnologyAutomatically enhances and amplifies the sound of the human voicefrequency range to provide high-quality dialogue when background noiseswells.


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TOP PORTIONBOTTOM PORTION

Remote Control Familiarizationemote Control Familiarization


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Accessing the Service Menuccessing the Service Menu

REMOTETOP PORTION

SIDE KEYS

To access the Service Menu.1) Turn the Set On2) Simultaneously, Press and

Holdthe Menu Key on the

Side Key pad and Press andHoldthe Menu Key on theRemote approximately 5seconds.

3) If Customers Menu appears,

continue to hold until itdisappears.4) The Service Menu appears

Note: If a Password is required to enter theService Menu. Enter;

0000


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Rear and Side Input Jacksear and Side Input Jacks

Main PWB

Orientation

Rear Input Jacks

USB Port

For Software

Upgrades Only


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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 Enterbutton using the remote control.

6) You can see the download progress Bar.7) Do not unplug until unit has automaticallyrestarted.

8) When download is completed, you will seeCOMPLETE.

9) Your TV will be restarted automatically.

Software Upgrade Procedureoftware Upgrade Procedure

Shows the

Currently

Installed

Version

Shows the

SoftwareVersion

found on the

USB Flash

Drive Shows the

Software file 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.


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42LH20 Dimensions

7-7/8"

200mm

25-11/16"

655mm

12-7/8"

327.5mm

40-3/8"

1028mm

Remove 4 screws to

remove stand for

wall mount

Model No.

Serial No.

Label

16-1/8"

410mm

20-1/16"

510mm

28-1/8"715.4mm

3-3/8"87.8mm

11-5/8"

297mm

Center

7-7/8"

200mm

3-9/16"

90mm

8-3/8"

223mm

9-1/16"

230mm

2-3/8"

60.4mm

Weight:

With Stand: 38.3 lbs / 17.4 kg

Without Stand: 32.3 lbs / 15.6 kg

There must be at least 4 inches of Clearance on all sides

42LH20 Product Dimensions42LH20 Product Dimensions

17


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Removing the Back Step (1)emoving the Back Step (1)

Remove the Stand by

Pulling it out of its

Retaining bracket.

Lay the TV down on its face. Remove the 4 screws

around stand indicated by the arrows.

Remove the one screwhidden by the stand.

Reinsert the

stand and

stand the unitupright for

service position

to continue

removing the

back cover.

Remove


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The Stand has to be removed first.

Remove the 22 screws indicated.

Pay attention to the size and type of screw

as there are many different types.

Putting in the improper screw when

reassembling may Cause damage.

Remove the one screw hidden

under the stand.

See previous page.

Removing the Back Cover Step 2 (Stand has to be removed)emoving the Back Cover Step 2 (Stand has to be removed)


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Circuit Board Layoutircuit Board Layout

POWER SUPPLY

(Includes Ballast)

Main PWB

LVDS

Cable

BacklightConnection

To Right Side

T-CON Under Shield

Ft IR/LED Control

ACInput

RFInput

Speaker R

RearInputs

BacklightConnection

To Left Side

Power Switch

Side Keywith

Power Button

Speaker L

T-CON p/n: EAT60663801


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Power Supply PWB Removalower Supply PWB Removal

Disconnect P201, AC In

and SK102, P401 and

P402.

Remove the 6 screwsindicated by the arrows.

P201

ACIn

SK102

P402

P401


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There are three types of Main Power switch used in LG televisions.

Type 1: Shuts of f AC to the Power Supply.

Type 2: Opens ground to the front IR board. (Stand-By 5V Remains, the Main board stays alive).

This prevents any activity of the IR or the Key Board. When the Switch is opened, a line called Power Key pulls up highwhen ground opens. When the switch is closed, this same line called Power Key feeds back to the Microprocessor and theMicro. Turns on the Power.

Type 3: Opens ground to the front IR board. (Stand-By 5V turns off, the Main board is dead).

This prevents any activity of the IR or the Key Board. When the Switch is opened, a line called Power Key pulls up highwhen ground opens. This line feeds back to the Main board and from there it routes to the Power Supply. The high tells theController chip to turn off STBY-5V. When the switch is closed, this same line called Power Key now goes high and feedsback to the Power Supply and tells the controller chip to turn STBY-5V on.

Power Supply (Main Power Switch Type 1) Locationower Supply (Main Power Switch Type 1) Location

On Off

If the TV wont come on, be sure to check the MainPower Switch before assuming a failure has occurred.

This switch breaks AC to the SMPS.

MAIN POWER SWITCH LOCATION

(Bottom Left Side viewed from rear)


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Power Supply (SMPS) PWB Layoutower Supply (SMPS) PWB Layout Hot Ground Shock Hazard

To Main

P201

AC IN

SK101

F1006.3A/250V

AC IN

F5013.15A/250VRun 380V

STBY 168VFrom Hot Gnd

ToMaster Power Switch

SK102

L

N

Pin 1 Pin 2

To Backlights

Left SideP402

To BacklightsRight Side

P401

42LH20 Power Supply Turn On Sequence42LH20 Power Supply Turn On Sequence


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T-CON PWB

12V LVDSAlong with VideoOn LVDS cable

Inverter OnStarts the BallastBacklights Light

135V B+ for theBallast

StandBy 5V

Power Button

Or Remote Key

Reset ofMainBoard

5VSwitch

PWROn

12V VideoProcessing

InvOn

BallastControl

IC

135VRegulator

12V/24VRegulators

OtherRegs

StandBy 5V Reg

1

2 6 66 8

8

6

3

5

6

6

6

Primary side fuse:

Stand-By 168VRun 380V

4

24VAudio

12V 24V

8

RegFor

Micro

LVDS

12VSwitch

12V

7

7

At point TV is inStand-By state.Energy Star compliant.Less than 1 Watt

4

Other Circuits5V General

A-DIMFixed

P-DIM

Manipulates Backlights

OtherCircuit

s

9

Cust Menu

for Backlight

PictureContent

PowerOn

3

8

Ballast Section

Of the Power Supply

No ACDet inthis

model

ToBacklights

LVDS Panel Control

Inv On/Off

Microprocessor IC100

Also Video Processor

LVDSVideo

12V

Power On

AC In

Ft Contro l

Analog

Dimming D

igital

Dimming

Bridge

Master(Main)

Power Sw

On

Off

L

42LH20 Power Supply Turn On Sequence42LH20 Power Supply Turn On Sequence

25


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Power Supply (SMPS) PWB Operational Troubleshootingower Supply (SMPS) PW B Operational TroubleshootingPower Supply Troubleshooting

Ac voltage is supplied to the Power Supply at Connector SC100. This set does not use AC Detect.The AC input generates a Hot Ground primary power supply that runs in two states, Stand-By (168) andRun (380V) measured at Fuse F501. This primary voltage develops all other voltages that are outputfrom the power supply. During Stand-By, the 5 Volt Standby should be present at connector P201, Pins7,8,9 or 10. If Missing remove AC Power and unplug Connector P201, apply AC Power and recheck forpresence of 5 Volt Standby. Loss of 5 Volt Standby would be a Power Supply Failure. Presence of 5 Volt

Standby would be an indication of a failure on the Main Board or possibly the Front PWB (IR) assembly.Suspect a possible short circuit loading the supply. Remember to observe the Front Power IndicatingLED this may save some time. A lit LED indicates the Stand-By 5V voltage is present!

The Main Board sends two commands to the Power Supply Board one being PWR the other is INV ON.These two voltages are used to control the power on turn on sequence. First via PWR (Pin 2) also knownas POWER ON, activates the internal Ballast voltage and the 24 Volt and 12 Volt lines to the Main board.

The 2nd

command is INV ON (P201 pin 20). It itthe Lamp Lighting Command Signal.If either command (PWR-ON or INV-ON) is missing it will result in a no picture symptom.

These voltages can easily be checked with the volt meter! Remove AC Power, unplug the two Connectorsto the backlights P401/P402. Reapply AC Power and press the ON-OFF Button on either the RemoteControl or Power Button on the Unit. Watch for the Power ON LED to change color from red to blue. This isan indication the PWR Signal was created on the the Main board. Check P700 or P201 pin 2 for the PWR-ON command (2.8V) to the Power Supply. Check P201 for 24V (Pins 17 or 18) and 12V (Pins 13 or 14).Confirm Pin 20 of P201 went to 3.3V. This is the INV ON signal needed to light the Lamps.Problems with either voltage can be easily solved by following the simple steps on the next page.


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TEST 1 Power Supply PWB Low Voltage TestEST 1 Power Supply PWB Low Voltage TestAC Should not be applied at any time while adding resistors or while

unplugging connectors as damage to the circuit PWB may occur.

a) The SMPS PWB MUSTbe producing STBY 5V on any of thepins 7, 8, 9 or 10 (5V).

If 5V Standby is not being generated, the SMPS PWB is defective andmust be replaced. There is no need to continue with the next test.

(b) Unplug P700 on the Main PWB.

TEST 1:

(1) Add a 10K resistor between (5V STBY) pin 7, 8, 9 or 10 and Pin 2(PWR). Apply AC. This will turn on the power supply.

Check that the 24V and 12V power supplies areturned on, P201 (24V pins 17 and 18) (12V pins 13 and 14)

(2) Remove AC power.

Use P700Side to insert

resistors


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Continue if the 1st test was successful. Leave original 10K resistor in

place.

(3) Add another 10K resistor between (5V) pin 7, 8, 9 or 10 andPin 20 (INV On).

(4) Apply AC Power. This simulates a Power On and Backlight On command.

Observe the Backlights.

a) If normal, the backlights should turn on.b) If the do not, recheck connectors P401 and P401.

(Warning: Disconnect the AC Power first).

These pins carry 1.2Kv when active.

c) Confirm the INV On/Off line Pin 12 is going to at least 3V.

d) If no backlight activity, SMPS is defective.

TEST 2 Power Supply PWB Backlights TestEST 2 Power Supply PWB Backlights TestP700 Connector disconnected from the Main PWB.

Apply AC after adding jumpers.

Use P700Side to insert

resistors


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Power Supply Connector P201 Voltage and Diode Checkower Supply Connector P201 Voltage and Diode Check

Diode Mode values taken with all Connectors Removed

0.886V4.98V0VPWR-ON2

GndGndGndGnd4

GndGndGndGnd6

1.67V5.14V5.14V5V8

1.67V5.14V5.14V5V10

GndGndGndGnd12

0.96V12.3V0V12V14

GndGndGndGnd16

0.71V21.4V0V24V18

1.6V3.8V0VINV.ON20

Open0V0VErr Out22

1.68V3.2V0V2PDIM24

Diode

CheckRunSTBYLabelPin

P201 Even " SMPS" to P700 "Main PWB"

ncncncnc1

GndGndGndGnd3

GndGndGndGnd5

1.67V5.14V5.14V5V7

1.67V5.14V5.14V5V9

GndGndGndGnd11

0.96V12.3V0V12V13

GndGndGndGnd15

0.71V21.4V0V24V17

ncncncnc19

Open1.66V0V1A.DIM21

ncncncnc23

Diode


P201 Odd "SMPS" to P700 "Main PWB"

1ADIM Pin 21 Fixed and not used 2PDIM Pin 24 can vary according to type of signalbeing processed and the OSD Backlight setting.0.6V 0% to 3.3V 100%. Output from the BCM chip.


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Power Supply Connector SK101 and SK102 Voltage and Diode Checkower Supply Connector SK101 and SK102 Voltage and Diode CheckDiode Mode values taken with all Connectors Removed

AC Voltage Readings Across Pins 1 and 2for STBY and RUN.

OLN2

OL120Vac

L1

Diode CheckRunSTBYLabelPin

AC Voltage Readings for either pin 1 or pin2 in STBY and RUN with one lead onNeutral of SK101.

OLn/a2

OL120Vac

n/a1


SK101 "SMPS" to AC IN SK102 "SMPS" to MASTER POWER SWITCH

SK102 SK101

Bottom Right of SMPS

Live

Neutral

With the Master Power SwitchClosed (On) AC flows.

When Open (Off) AC open and doesnot flow.


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General Backlight Informationeneral Backlight Information

To Backlights

Over 1.2KV

Currently, number of lamps Unknown

To BacklightsOver 1.2KV

Ballast Section of SMPS

EEFL (External Electrode Fluorescent Lamp)LOW COST Large number of lamps driven by a single inverter


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Simple structure, Low price

Complicated structure

Simple structure

Lamp manufacturing processLamp assembly structure

Low Cost

Large number of LampDrive by single inverter

EEFL Compared to CCFLEFL Compared to CCFL


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Key: Long Li fe Time

For CCFL, Hg gas is consumed mainly near the internal electrodeFor EEFL, longer life time is expected because there is no internal electrode consuming Hg gas

EEFL Bulb Design Compared to CCFLEFL Bulb Design Compared to CCFL


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Ballast PWB Layoutallast PWB Layout

To BacklightsLeft Side T703

T704

Viewed from rear

To BacklightsRight Side

SMPS PWB

BacklightsTest PointBottom of

R406 or R40338V P/P

1.2Kv

42LH20 P700 Main Board to Power Supply P201 Ballast Turn On Circuit42LH20 P700 Main Board to Power Supply P201 Ballast Turn On Circuit


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IC100

BCM

R743 100

R7191K

R704 4.7KA-DIM

PWM-DIM

INV On/Off3.8V

VBR-B (PWM Dimming) Manipulates the Backlight Brightness via Customers OSD.Manipulates the Backlight Brightness via the BCM Chip. Darker Picture, Darker Backlights to facilitateimproved Contrast Ratio. 0.6V ~3.3V Range

INV-On/Off

PWB-0AB12

AB13 PWM-2

20

24

21

R189 100

R185 1.2K

R244100

G5

VBR-A (Analog Dimming)This line is not used.

P700POWER SUPPLY

RL-ON

PWR

4.89V

2

12VReg

24VReg

13

14

17

18

380V

BALLAST

SECTION

1.67V

IC301

380VReg

160VReg

ERROR-OUT

0V22

P201MAIN PWB

20

24

21

2

13

14

17

18

22

IC600Ballast Control IC

12V

24V

On Back of PWB

On Back of PWB

INV

On/Off

To Backlights

1.2Kv

Two

T

ransformers

D

riveCircuit

FETsQ709/10

Drive Control

Q702

R704 4.7K

R7590

R714100

GPIO 134

GPIO 136

R237100

Q701

Q700

R703R706

E5

7 8

9 10

7 8

9 10STBY5V

STBY5V

L700

L733

Ballast

Power

Hot Gnd

390V

P401

P402

Stand By 5VReg

Controller

R7173.3K

+5V General

16

0V

160V

36

E8GPIO 197

ERROR-OUT

R201 100

0.3V~3.3V

Active 5V

The Error Line will: Pulse high when the backlights 1st attempt to fire, if they do it goes back low. If the do not, it goes low, then thebackights attempt to fire again and it pulses high. This happens 4 times, on the 5th attempt it goes high and shut off the television


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Power Supply Backlight Drive Signal Effectsower Supply Backlight Drive Signal Effects

VBR-B

PWM-DIM manipulatesthe ballast drive IC.

VBR-A

BR1 (A-DIM) is not used.

Waveform taken using loose coupling. Clip the

probe to one of the Backlight wires. Use

caution, there is 1.2Kv in the wire.Slow scope setting to 2.4mSec to see the effects

of PWM on the waveform.

The PWM amount can cause the frequency to be

measured differently.


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LCD Controller Board

The T-Con IC UC1 receives from the Main Board at CN5 12 BitLVDS Signals (Video) which it processes into TFT Drive Signals which throughconnectors CN3 and CN4 controls the LCD Panel.

12V is supplied to the T-Con Board on connector CN5 from the Main Board

(easily measured at fuse F1).

Diode LED1 is a boot up indicator and is helpful in troubleshooting as a quickindication of a loss of supply and or a Boot Up problem.

There are two DC to DC converters that create(17V developed at the cathode of D14) and(3.3V developed at the cathode of D13).

The 3.3V can also be measured at the ribbon connectors delivering signals tothe TFT panel(CN3 pins 57, 58 or 59) and(CN4 pins 2, 3 or 4).

T-CON BOARD SECTIONON BOARD SECTION


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T-CON (TFT Drive) Board RemovalON (TFT Drive) Board Removal

Remove the 3 Screws in the T-CON shield

and remove the shield

CN4 CN3

CN5

Disconnect CN3, CN4 and CN5.

See next slide for details.

The two screws shown in the picture below are

for the Service Posit ion.

They would have been removedwhen removing the shield.

Be sure to reinstall them if

servicing the T-CON PWB.


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To remove the flex cables to the TFT Panel,CN3 or CN4: Place a soft thin object like afingernail underneath the black locking taband gently pull forward.

(Shown by the arrows in Fig 1)

Fig 1

Fig 2

Unlocked

Flip the lock up and back from the flex cable.Then the flex cable can be easily removed. To remove the LVDS cable CN5;

Press in on the two tabs and slowly rockthe cable out of the connector.

(Shown by the arrows in Fig 3)

Fig 3 (CN5) LVDS

UNLOCKING CN3, CN4 and CN5NLOCKING CN3, CN4 and CN5

The locking tab is flipped upward

Press In Press In

Pull Out

CN3 or CN4 Locked

T-CON Board Removal (Continued)ON Board Removal (Continued)


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LVDS (Video and 12V) from Main PWB

T-CON Board (With Shield)ON Board (With Shield)


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T-CON (TFT Drive) PWB (Shield Removed)ON (TFT Drive) PWB (Shield Removed)

U7

D13

U9

LED1

F1

CN4 CN3

CN5

UC1

To

Main PWB

To TFT Panel To TFT Panel

Remember to replace screws for

ground purposes if testing the PWB.

D14FL114

T-CON p/n: EAT60663801

U LED1 t d t i if


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T-CON (TFT Drive) PWB ChecksON (TFT Drive) PWB Checks

T-CON

PWB

LED1 Use LED1 to determine if

The boot up sequence of

The T-CON is OK.

This LED will turn bright Blue

Short ly after power is applied

then go out shortly after

backlights illuminate if all is OK.

Power Off Power 1st On

Anode 0V

Cathode 0V

Anode 3.3V

Cathode 0V

Power On

Anode 3.3V

Cathode 1.3V

LED OFF LED ON LED OFF

1.8V3.3V 0V

U10

Check the RegulatorU10 for Correct Voltage

Check Fuse

F1 for 12V

F1

CN5

Cathode

16.9V

Cathode

3.3V

D14

D13

Anode

Cathode

From Pins 2,

3, 4 and 5.

T-CON (TFT Drive) Voltages for the Panel ChecksON (TFT Drive) Voltages for the Panel Checks


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12VU7B+

3.3V

VCC26V

VGH_M

Pin 8

16V

VDD

-5V

VGL

T-CON (TFT Driver) Board CN3 and CN4 (3.3V Voltage Check)ON (TFT Driver) Board CN3 and CN4 (3.3V Voltage Check)


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CN4

3.3V Check3.3V Check

If the 3.3Volts is missing,

check the 3.3V DC to DC

converter. Check at D13

cathode.

See previous page for

location.

CN3

T-CON PWB

T-CON PWB Connector CN5 to Main PWB Voltage and Diode CheckON PWB Connector CN5 to Main PWB Voltage and Diode Check


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CN5 CONNECTOR "T-CON PWB to P801 "Main"

*Pin 29 PWM-DIM 3.15V (Max 100%) to 0.6V (Min 0%)Customers Menu Backlight setting. But is Not Used byT-CON.

1.1V1.2V0VTXA1-16

GndGndGndGnd15

0.8V1.1V0VTXA0+14

1.1V1.2V0VTXA0-13GndGndGndGnd12

1.1V0V0VOPC-EN11

Open0V0VLVDS-SEL10

GndGndGndGnd9

GndGndGndGnd8

GndGndGndGnd7

GndGndGndGnd6

1.6V12.1V0VLVDS 12V5



1.6V12.1V0VLVDS 12V2GndGndGndGnd1

GndGndGndGnd32

GndGndGndGnd31

GndGndGndGnd30

1.1V3.1V0V*PWM-DIM29Open3.3V0VOPC-OUT28

GndGndGndGnd27

1.1V1.2V0VTXA3+26

1.1V1.2V0VTXA3-25

GndGndGndGnd24

1.1V1.2V0VTXAC+23

1.1V1.1V0VTXAC-22

GndGndGndGnd21

1.1V1.1V0VTXA2+20

1.1V1.2V0VTXA2-19

GndGndGndGnd181.1V1.1VGndTXA1+17

NOTE: The outside pins on each side are actually notcounted, they are both ground. But they are counted inthe table. (See arrow on the T-CON PWB CN5)

MAIN BOARD SECTIONAIN BOARD SECTION


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Input Signal Processing

IC100 is the main Microprocessor and the main Signal Processor and is responsible for :

ATSC, NTSC, and QAM reception and processingRS 232 service only Port (software upgrades and home theater environment).Wired Remote Port

(1) Component Input Y, Pr, Pb and Audio L R(2) HDMI Inputs (back) (1) HDMI (Side Input)RGB PC and (PC Audio)USB (software upgrades using flash drive). USB located on the Rear, no Side Inputs.AV Composite

SIF and SAP Output Signals

10 Bit LVDS (10 Pin) to the T-CON BoardAudio output signals to the SpeakersDigital Audio Output Coaxial and Optical

ON OFF Controls to the SMPS turning on low voltage generation and BacklightsBacklight intensity control signal (Digital Dimming) P-DIM

Removing the Main PWBemoving the Main PWB Flipthe locking tabsupward,ll th LVDS ribbon out


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Remove the one

screws at the bottomof the Decorative

plastic piece on the

right side. Remove the

plastic piece.

Remove the twopieces of tape on the

left side holding down

the cables and the one

at the top.

Remove the remaining

11 screws indicated by

the arrows.

Decorative

Plastic

P700

P801

P600

P1204

pull the LVDS ribbonout.

NOTE: Be sure to check

on top and behind the

Video Processor IC.Look for a piece of

Chocolate

(Heat Transfer Material).

Be sure to transfer to

new PWB if present.

Main PWBain PWB VIDEO PROCESSORP801 T CON PWB

Look carefully on top and

behind the Video Processor


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Layoutayout IC100 RUNS HOT,THIS IS NORMAL.

1

19

LD1000

Tuner OK

when

Green

P700

P801

P1204

IC100

Microprocessor

andVideo Processor

X100

USBTuner

TU1001

To SMPS

To Front PWB

Assembly

P801 to T-CON PWB

To Speakers

IC for Chocolate (Heat

Transfer) material.

Be sure to transfer to new

PWB if replaced.

For

Software

Upgrade

via Jig

SW100

ResetX105

P600

LD1000

Main PWBain PWBVoltages given on the 11X17 foldout Interconnect Diagram


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(Back View)Back View) Voltages given on the 11X17 foldout Interconnect Diagram

IC1003

IC1002

Tuner

IC702

IC601

IC500IC501

IC501

IC102

42LH20 Main Board (Front View) Component Layout42LH20 Main Board (Front View) Component Layout

IC704 IC705


51/74

51

MAIN (Digital) Board

ToSpeakers

ResetIC100

IC1004

8vsb/

QAM

Q7061 (5V)2 (0.48V)3 (0.48V)

4 (6V)5-6 (12.3V)7-8 (5V)

IC600Audio56 Pin

1

To

SMPSPWB

L726

L710

Q706 Switch(12V LVDS)(5V General)

X1005

25 Mhz

X10012 Mhz

IC1003

IC701

P600

P700

P1204

TUNER

16 SIF

19 Video

4 (5V)

12 DIF +13 DIF -

15 (5V)

LD1000

To FrontControl

IC101

IC105

IC1000

IC7043.3V-FE1 (0.78V)2 (Gnd)

3 (5V)4 (7.4V)5 (2.12V)6 (3.28V)7 (3.28)8 (5V)

IC7051.26V_VDDC

1 (0.78V)2 (Gnd)

3 (5V)4 (5.9V)5 (5V)6 (1.3V)7 (1.3V)8 (3.16V)

IC7011.8V_DDR

1 (N/C)2 (3.18V)

3 (3.18V)4-5 (N/C)6 (1.87V)7 (0.8V)8 (Gnd)

Q702Inv-On Control

Gnd0V

(0.6V)

3.85V (0V)

IC10001.2V_PVSB

1 (N/C)2 (3.2)3 (3.2V)4-5 (N/C)6 (1.2V)7 (0.8V)8 (Gnd)

IC105HDCP EEPROM

1-2 (Gnd)

3 (5V)5-6 (0V)4-7 (Gnd)6 (1.2V)7 (0.8V)8 (5V)

IC101Flash Memory

1-2 (0V)3-4 (0V)5-6 (0V)

7-8 (3.2V)

IC107Power Det

1 (3.28V)

2 (Reset) .3V3 (Gnd)

IC107

IC7043.3V_FE

IC7051.26V_VDDC

Grayed Out ICs are located on Back

IC100

P801

( ) =Off

0V 0.6V)

To T-CON(LVDS)

IC100Micro and Video

Processor

Mstar Chip

E

C

B

KEY

Main PWB X100 and X1005 Checkain PWB X100 and X1005 Check


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X1005LocationX100

Location

2.28Vp/p

12Mhz

Set on or off

X400

IC100 Microprocessor Crystal

MAIN PWB

4.95Vp/p

25Mhz

X1005

Tuner Control IC1004 Crystal

Only when set is on

X100

Main PWB LD1000 Functionain PWB LD1000 Function


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MAIN PWB

Main PWB

LD1000 Location

LD1000

Use LD1000 as a visual aid.

This lets you know if the tuner internal PLL

(Phase Locked Loop) system is locked.

Illuminated PLL is normal.

Off is abnormal tuner lock.

Main PWB Tuner w ith Shield Off (Pin ID)ain PWB Tuner with Shield Off (Pin ID)


54/74


1

19

18

4

13

12

9

8

Main PWB Tuner Video and SIF Output Checkain PWB Tuner Video and SIF Output Check


55/74


MAIN PWB

Tuner Location

450mVp/p

Pin 19

Video

Signal

Pin 16

SIF

Signal

2.24Vp/p

USING COLOR BAR SIGNAL INPUT

Pin 12 and Pin 13

Dig IF Signal

Note:

Dig IF Signal only when

receiving a Digital Channel.700mVp/p

Pin 1

Note: Video Out Signal only when

receiving an analog Channel.

Main PWB Tuner Clock and Data Linesain PWB Tuner Clock and Data Lines


56/74


Pin 8 SDA

100uS1V per/div 5V p/p

Pin 9 SCL

100uS1V per/div 5V p/p

Note:

SCL and SDA only active duringan actual Channel Change.

Main PWB LVDS P801 Video Output Checkain PWB LVDS P801 Video Output Check


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MAIN PWB

P801Location

To confirm that the Main PWB is outputting Picture Content signals, check P801 (LVDS)

cable for output. Check pins 6-7,12-13 15-16 and 18-19. Pins 9-10 carry the clock. Thesesignals vary from each other, but looking for signals like the ones shown below on any ofthese pins will confirm the output of video content. This signal is using standard SMTE ColorBar output from a generator as the input source.

Pin 1

Pin 18

This is just a sample of two pins on the LVDS.

There are 8 pins on P801 carrying video.

2uS

500nS

2uS

500nS

Pin 30

Pin 30, 29, 28, 27 (LVDS 12V)

P801

Pin 6

Main PWB LVDS Connector P801 Pin Identificationain PWB LVDS Connector P801 Pin Identification


58/74


12V forT-CONPWB

PWM Dim

Not used on

T-CON

Video

Video

Video

Video

Clock

Screen

Size

Video

30 1

P801

Main PWB Connector P801 to Tain PWB Connector P801 to T-CON Voltage and Diode CheckON Voltage and Diode CheckDiode Mode values taken withll C t R d


59/74


0V

0V

0V

0V

Gnd

Gnd

Gnd

Gnd

0V

0V

Gnd

0V

0V

Gnd

0V

SBY

1.6V12.1VLVDS 12V30

1.6V12.1VLVDS 12V29

1.6V12.1VLVDS 12V28

1.6V12.1VLVDS 12V27

GndGndGnd26

GndGndGnd25

GndGndGnd24

GndGndGnd23

Open0VLVDS-SEL22

1.1V0VOPC-EN21

GndGndGnd20

1.1V1.2VTXA0-19

0.8V1.1VTXA0+18

GndGndGnd17

1.1V1.2VTXA1-16

Diode

CheckRunLABELPin

all Connectors Removed

Gnd

Gnd

0V

0V

Gnd

0V

0V

Gnd

0V

0V

Gnd

0V

0V

Gnd

Gnd

SBY

1.1V1.1VTXA1+15

GndGndGnd14

1.1V1.2VTXA2-13

1.1V1.1VTXA2+12

GndGndGnd11

1.1V1.1VTXAC-10

1.1V1.2VTXAC+9

GndGndGnd8

1.1V1.2VTXA3-7

1.1V1.2VTXA3+6

GndGndGnd5

Open3.3VOPC-OUT4

1.1V3.1V*PWM-DIM3

GndGndGnd2

GndGndGnd1

Diode CheckRunLABELPin

P801 CONNECTOR "Main" to CN5 "T-CON PWB"

*Pin 3 PWM-DIM 3.15V (Max 100%) to 0.6V (Min 0%)Customers Menu Backlight setting. But is Not Used on T-CON.

Main PWB Connector P700 to Power Supply Voltage and Diode Checkain PWB Connector P700 to Power Supply Voltage and Diode CheckP700 M i PWB" t P201 SMPS PWB"


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Open3.2V0V2PDIM24

Open0V0VErr Out22

1.9V3.8V0VInv.Out20

Open21.4V0V24V18

GndGndGndGnd16

2.1V12.3V0V12V14

GndGndGndGnd12

1.1V5.14V5.14V5V10

1.1V5.14V5.14V5V8

GndGndGndGnd6

GndGndGndGnd4

1.87V4.98V0VPWR-ON2

Diode


ncncncnc23

2V1.7V0V1A.DIM21

ncncncnc19

Open21.4V0V24V17

GndGndGndGnd15

2.1V12.3V0V12V13

GndGndGndGnd11

1.1V5.14V5.14V5V9

1.1V5.14V5.14V5V7

GndGndGndGnd5

GndGndGndGnd3

ncncncnc1

Diode


1ADIM Pin 21 Fixed and not used 2PDIM Pin 24 can vary according to type of signalbeing processed, OSD Backlight setting. 0.6V 0%to 3.3V 100% and the Intelligent Sensor. Outputfrom the BCM chip.

P700 Main PWB" to P201 SMPS PWB"

Odd Pins Even Pins

Main PWB Connector P1204 to (Ft. IR/LED Control) Voltage and Dain PWB Connector P1204 to (Ft. IR/LED Control) Voltage and D iode Checkode CheckP1204 CONNECTOR "MAIN PWB" t P1 "F t IR / LED PWB A "


61/74



P1204 CONNECTOR "MAIN PWB" to P1 "Front IR / LED PWB Assy"

2.17V3.29V0VPOWER On/Off12

0.6V3.29V3.29V3.3V_ST11

GndGndGndGnd10

Open4.8V4.8VIR9

GndGndGndGnd8

GndGndGndGnd7

1.13V5.1V5.1V5V ST6

1.08V3.3V3.3VKey25

1.08V3.3V3.3VKey14

GndGndGndGnd3

1.14V3.3V3.3VSDA2

1.14V3.3V3.3VSCL1


Main PWB Connector P600 to Speakers Voltage and Diode Checkain PWB Connector P600 to Speakers Voltage and Diode Check


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SPK-L(+)

SPK-L(-)

SPK-R(+)

SPK-R(-)

LABEL

1.5V10.7V0V4

1.5V10.7V0V3

1.5V10.7V0V2

1.5V10.7V0V1

Diode CheckRunSBYPin

P600 CONNECTOR "Main" to "Speakers"

Use speaker out to test for defective Audio Amp IC600

FRONT IR BOARDRONT IR BOARDFront (IR and LED Control) Assembly Layout (Back View)


63/74

LCD March 2009 42LH2063

To Side Key PWB

The IR Sensor and Power LED control IC

are located on the front of th is Board

Cover

P1

P3 P1 To Main PWB

cc

cc

Front (IR and LED Control) Assembly Layout (Back View)

P3

Cover

Removed

Front PWB Assembly (IR and LED Control) Layout (Back View)ront PWB Assembly (IR and LED Control) Layout (Back View)


64/74


IR Sensor

POWER LEDS (LED1 through LED10)

Control IC U1

(Power LEDs)

Front IR/LED Control Connector P1 and P3 to Main Voltage and Diront IR/LED Control Connector P1 and P3 to Main Voltage and Diode Checkde Check


65/74



2V

Open

Gnd

2V

Gnd

Gnd1.5V

Open

Open

Gnd

2.4V

2.4V

Diode

Check

3.3V3.3VSCL1

3.3V3.3VSDA2

GndGndGnd3

3.3V3.3VKey14

3.3V3.3VKey25

5.1V5.1V5V ST6GndGndGnd7

GndGndGnd8

4.8V4.8VIR9

GndGndGnd10

3.29V3.29V3.3V_ST11

3.29V0VPOWER On/Off12

RunSTBYLABELPin

P1 Connector IR/LED Control PWB

to "MAIN PWB" P404P3 Connector IR/LED Control PWB

to Side Key" P3000

Gnd

Key2

Gnd

Key1

Label

Gnd

Open

Gnd

Open

Diode

Check

GndGnd4

3.3V3.3V3

GndGnd2

3.3V3.3V1

RunSTBYPin

KEY BOARD SECTIONEY BOARD SECTION


66/74


To Main PWBP3000

SW3008

SW3007

SW3006

SW3005

SW3004

SW3003

SW3002

SW3001

c c

Side Key Assemblyide Key AssemblyP3000 Diode Check Measurements with Key pressed.

KEYPin 3 measuredPin 1 measured

KEY


67/74


CH (Up)

CH (Dn)

Volume (+)

Volume (-)

KEY

10K Ohms

4.8K Ohms

1.8K Ohms

270.5 Ohms

from Gnd

10K Ohms

4.8K Ohms

1.8K Ohms

270.5 Ohms

from Gnd

Enter

Menu

Input

Power

KEY

P3000 Voltage Measurements with Key pressed.

CH (Up)

CH (Dn)

Volume (+)

Volume (-)

KEY

2.24V

1.65V

0.906V

0.179V

Pin 3 measured

from Gnd

2.24V

1.65V

0.906V

0.179V

Pin 1 measured

from Gnd

Enter

Menu

Input

Power

KEY

P3000 Connector Side Key" to IR/LED Control

PWB P1

Gnd

Key2

Gnd

Key1

Label

Gnd

Open

Gnd

Open

Diode Check

GndGnd4

3.3V3.3V3

GndGnd2

3.3V3.3V1

RunSTBYPin

c

REASSEMBLY NOTES:EASSEMBLY NOTES:


68/74


Pay attention to the wire

dress for the Side Key

PWB. These wires can get

pinched between the rear

cover and lower left hand

screw post. The wires can

be dressed to the right ofthe post in the slot

provided.

INTERCONNECT SECTION (11 X 17 Foldout)NTERCONNECT SECTION (11 X 17 Foldout)


69/74


This section shows the 11X17 foldout thathis section shows the 11X17 foldout that s available in the Paperavailable in the Paperand Adobe version of the Training Manual.nd Adobe version of the Training Manual.


70/74

42LH20 LVDS P801 WAVEFORMS

LVDS P801 PIN 4 (OPC-Out) LVDS P801 PIN 6 (TXA3+) LVDS P801 PIN 7 (TXA3-) LVDS P801 PIN 9 (TXAC+) LVDS


71/74

42LH20 P80

WAVEFORM

Waveforms RF input.

LVDS P801 PIN 12 (TXA2+) LVDS P801 PIN 13 (TXA2-) LVDS P801 PIN 15 (TXA1+) LVDS P801 PIN 16 (TXA1-)

LVDS P801 P IN 18 (TXA0+) LVDS P801 P IN 19 (TXA0-)

42LH20 Main Board (Front View) Component Layout42LH20 Main Board (Front View) Component Layout

Q7061 (5V)2 (0.48V)3 (0 48V) L726

Q706 Switch(12V LVDS)

IC1003IC7043.3V-FE1 (0.78V)2 (Gnd)

IC105HDCP EEPROM

1 2 (Gnd)

IC7043.3V_FE

IC7051.26V_VDDC

P801

To T-CON( )

E

C

B

KEY


72/74

MAIN (Digital) Board

ToSpeakers

ResetIC100

IC1004

8vsb/

QAM

3 (0.48V)4 (6V)

5-6 (12.3V)7-8 (5V)

IC600Audio56 Pin

1

ToS

MPSPWB

L726

L710

(5V General)

X1005

25 Mhz

X10012 Mhz

IC701

P600

P700

P1204

TUNER

16 SIF

19 Video

4 (5V)

12 DIF +13 DIF -

15 (5V)

LD1000

To FrontControl

IC101

IC105

IC1000

2 (Gnd)3 (5V)

4 (7.4V)5 (2.12V)6 (3.28V)7 (3.28)8 (5V)

IC7051.26V_VDDC

1 (0.78V)2 (Gnd)3 (5V)

4 (5.9V)5 (5V)6 (1.3V)7 (1.3V)8 (3.16V)

IC7011.8V_DDR

1 (N/C)2 (3.18V)3 (3.18V)

4-5 (N/C)6 (1.87V)7 (0.8V)8 (Gnd)

Q702Inv-On Control

Gnd0V

(0.6V)

3.85V (0V)

IC10001.2V_PVSB

1 (N/C)2 (3.2)3 (3.2V)4-5 (N/C)6 (1.2V)7 (0.8V)8 (Gnd)

1-2 (Gnd)3 (5V)

5-6 (0V)4-7 (Gnd)6 (1.2V)7 (0.8V)8 (5V)

IC101Flash Memory

1-2 (0V)3-4 (0V)5-6 (0V)

7-8 (3.2V)

IC107Power Det

1 (3.28V)2 (Reset) .3V

3 (Gnd)

IC107

Grayed Out ICs are located on Back

IC100

( ) =Off

0V 0.6V)

(LVDS)

IC100Micro and Video

ProcessorMstar Chip

IC1003P801IC1003

To Tuner 5VRegulator

E

C

B

KEY

42LH20 Main Board (Rear View) Component Layout42LH20 Main Board (Rear View) Component Layout

Q104Q104

Power Det


73/74

Main (Digital) Board

To Speakers

ResetSW100

1

IC1002

IC601(1.8V_Amp)

IC702

(3.3V_ST)

P600

P700

P1204

TUNER

16 SIF

19 Video

4 (5V)

12 DIF +13 DIF -

15 (5V)

To Front Control

IC104

EEPROM (Micro)

g1 (12V)

2 (Gnd)3 (8.94V)

IC1002Tuner 5V Regulator1 (8.94V)2 (2.37V)3 (5V)4 (N/C)

5 (Gnd)

IC7021 (5V)2 (3.3V)3 (0V)

IC6011 (3.2V)2 (1.8V)3 (0V)

IC500 / IC501HDMI EDID

IC500IC501

IC1200R,G,B PC/DDC

IC102

NAN FlashMemory

1-4 Gnd5 4.82V6 4.82V7 4.82V8 4.82V

IC501/IC5011-4 Gnd

5 4.82V6 4.82V7 4.82V8 4.82V

IC12001-4 Gnd

5 4.82V6 4.82V7 4.82V8 4.82V

Audio Mute SwitchB 0.08VC 3.26VE Gnd B

C

E

Q600

IC103

12

3

IC103Reset Gen1 Gnd2 3.26V3 3.26V

Q600

Q600Power On DelayB 0.08VC 1.95VE Gnd

Q102 Q103Q104

Q102

Power Det 12VB 0.78VC 0VE Gnd

Q103Power Det 5VB 0.08VC 3.3VE Gnd

Power DetB 0.08V

C 3.3VE Gnd


74/74

42LH202LH20This concludes the 42LH20

training session.

Direct View LCD

42lh20 presentation

Documents