LG 42LH20 Series Service Manual Download Page 73

Page: 73 / 74

Main (Digital) Board

To Speakers

Reset

SW100

IC1003

IC1002

IC601

(1.8V_Amp)

IC702

(3.3V_ST)

P801

P600

P700

P1204

TUNER

16 SIF

19 Video

4 (5V)

12 DIF +

13 DIF -

15 (5V)

To Front Control

IC104

EEPROM (Micro)

IC1003

To Tuner 5V
Regulator
1 (12V)
2 (Gnd)
3 (8.94V)

IC1002

Tuner 5V Regulator
1 (8.94V)
2 (2.37V)
3 (5V)
4 (N/C)
5 (Gnd)

IC702
1 (5V)
2 (3.3V)
3 (0V)

IC601
1 (3.2V)
2 (1.8V)
3 (0V)

KEY

42LH20 Main Board (Rear View) Component Layout

IC500 / IC501

HDMI EDID

IC500

IC501

IC1200

R,G,B PC/DDC

IC102

NAN Flash

Memory

1-4 Gnd
5 4.82V
6 4.82V
7 4.82V
8 4.82V

IC501/IC501
1-4 Gnd
5 4.82V
6 4.82V
7 4.82V
8 4.82V

IC1200

1-4 Gnd
5 4.82V
6 4.82V
7 4.82V
8 4.82V

Audio Mute Switch
B 0.08V
C 3.26V
E Gnd

Q600

IC103

Reset Gen
1 Gnd
2 3.26V
3 3.26V

Q600

Q600
Power On Delay
B 0.08V
C 1.95V
E Gnd

Q102 Q103

Q104

Q102

Power Det 12V
B 0.78V
C 0V
E Gnd

Q103

Power Det 5V
B 0.08V
C 3.3V
E Gnd

Q104

Power Det
B 0.08V
C 3.3V
E Gnd

Summary of Contents for 42LH20 Series

Page 1: ...42LH20 42LH20 Direct View LCD Original March 2009 Updated February 11 2010 ...

Page 2: ...cuit 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 ...

Page 3: ...h 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 Assem...

Page 4: ...ectronics 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 ...

Page 5: ... 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 ...

Page 6: ...0 847 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 Huntsville 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 5...

Page 7: ... Use caution when dealing with these IC and circuits Always handle the circuit boards on the outside edges while using ESD protection 5 Exercise care when making voltage and waveform checks to prevent costly short circuits from damaging the unit 6 Be cautious of loose screws and other metal objects to prevent a possible short in the circuitry 1 Check the appearance of the Replacement Panel and Cir...

Page 8: ...amination 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 Diode Check for possible short circuits Isolate To further isolate the failure check for the proper waveforms with the Oscilloscope to make a final determinati...

Page 9: ...February 2009 42LH20 9 This section of the manual will discuss the specifications of the 42LH20 LCD Direct View Display Panel 42LH20 Product Information 42LH20 Product Information ...

Page 10: ...eady 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 178º 178º 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 ...

Page 11: ...ality sound FORMATS 480I 480P 1080I 720P 1080P Interlaced Progressive Interlaced Progressive Progressive Interlaced 2 Fields to make a Frame Progressive Each Field is a Frame 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 24FPS 30FPS 60FPS BASIC PIXEL COUNTS 720P Panel 1365 H 768 V 1080P Panel 1920 H x 1080 V Pixel ...

Page 12: ...OGO Familiarization Page 1 SIMPLINK Allows for convenient control of other LG SimpLink products using the existing HDMI connection Clear Voice Technology Automatically enhances and amplifies the sound of the human voice frequency range to provide high quality dialogue when background noise swells ...

Page 13: ...LCD or PLASMA 2009 Model 13 TOP PORTION BOTTOM PORTION Remote Control Familiarization Remote Control Familiarization ...

Page 14: ...Service Menu 1 Turn the Set On 2 Simultaneously Press and Hold the Menu Key on the Side Key pad and Press and Hold the Menu Key on the Remote approximately 5 seconds 3 If Customer s Menu appears continue to hold until it disappears 4 The Service Menu appears Note If a Password is required to enter the Service Menu Enter 0000 ...

Page 15: ...February 2009 42LH20 15 Rear and Side Input Jacks Rear and Side Input Jacks Main PWB Orientation Rear Input Jacks USB Port For Software Upgrades Only ...

Page 16: ... 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 Upgrade Procedure Software Upgrade Procedure Shows the Currently Installed Version Shows the Software Version found on the USB Flash Drive Shows the Software file found o...

Page 17: ...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 Dimensions 42LH20 Product Dimensions 17 ...

Page 18: ... will have a better understanding of the disassembly procedures the layout of the printed circuit boards and be able to identify each board Troubleshooting This section of the manual will also discuss troubleshooting Upon completion of this section the Technician will have a better understanding of how to diagnosis and resolve problems DISASSEMBLY AND TROUBLESHOOTING SECTION DISASSEMBLY AND TROUBL...

Page 19: ... 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 screw hidden by the stand Reinsert the stand and stand the unit upright for service position to continue removing the back cover Remove ...

Page 20: ...n 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 Removing the Back Cover Step 2 Stand has to be removed ...

Page 21: ...t POWER SUPPLY Includes Ballast Main PWB LVDS Cable Backlight Connection To Right Side T CON Under Shield Ft IR LED Control AC Input RF Input Speaker R Rear Inputs Backlight Connection To Left Side Power Switch Side Key with Power Button Speaker L T CON p n EAT60663801 ...

Page 22: ...February 2009 42LH20 22 Power Supply PWB Removal Power Supply PWB Removal Disconnect P201 AC In and SK102 P401 and P402 Remove the 6 screws indicated by the arrows P201 AC In SK102 P402 P401 ...

Page 23: ...he 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 high when ground opens This line feeds back to the Main board and from there it routes to the Power Supply The high tells the Controller chip to turn off STBY 5V When the switch is closed this same line called Power Key now goes high and feeds back to the Power Sup...

Page 24: ...t Power Supply SMPS PWB Layout Hot Ground Shock Hazard To Main P201 AC IN SK101 F100 6 3A 250V AC IN F501 3 15A 250V Run 380V STBY 168V From Hot Gnd To Master Power Switch SK102 L N Pin 1 Pin 2 To Backlights Left Side P402 To Backlights Right Side P401 ...

Page 25: ...V 24V 8 Reg For Micro LVDS 12V Switch 12V 7 7 At point TV is in Stand By state Energy Star compliant Less than 1 Watt 4 Other Circuits 5V General A DIM Fixed P DIM Manipulates Backlights Other Circuits 9 Cust Menu for Backlight Picture Content Power On 3 8 Ballast Section Of the Power Supply No AC Det in this model To Backlights LVDS Panel Control Inv On Off Microprocessor IC100 Also Video Process...

Page 26: ... 17 20 19 22 21 23 24 2 1 4 3 6 5 8 7 10 9 11 12 14 13 16 15 18 17 20 19 22 21 23 24 21 3V 24V Gnd Gnd Gnd Gnd Gnd Gnd n c n c n c n c E5 GPIO 134 L706 L704 24V C721 68uF C727 68uF L707 12V C720 0 1uF C722 47uF L701 Q701 R703 R706 R237 G5 R719 1KΩ Q702 R759 0Ω R717 3 3KΩ GPIO 136 R244 100Ω 5V General Power On Inverter On Off 3 1 2 6 5 8 7 Q706 5V L715 5V General L714 LVDS 12V Panel Power L728 Q703...

Page 27: ...ndicates 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 known as 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 it the Lamp Lighti...

Page 28: ...TBY 5V on any of the pins 7 8 9 or 10 5V If 5V Standby is not being generated the SMPS PWB is defective and must 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 are turned on P201 24V pins 17 and 18...

Page 29: ...ts 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 Test TEST 2 Power Supply PWB Backlights Test P700 Connector disconnected from the Main PWB A...

Page 30: ...NV ON 20 Open 0V 0V Err Out 22 1 68V 3 2V 0V 2 PDIM 24 Diode Check Run STBY Label Pin P201 Even SMPS to P700 Main PWB nc nc nc nc 1 Gnd Gnd Gnd Gnd 3 Gnd Gnd Gnd Gnd 5 1 67V 5 14V 5 14V 5V 7 1 67V 5 14V 5 14V 5V 9 Gnd Gnd Gnd Gnd 11 0 96V 12 3V 0V 12V 13 Gnd Gnd Gnd Gnd 15 0 71V 21 4V 0V 24V 17 nc nc nc nc 19 Open 1 66V 0V 1 A DIM 21 nc nc nc nc 23 Diode Check Run STBY Label Pin P201 Odd SMPS to P...

Page 31: ...ross Pins 1 and 2 for STBY and RUN OL N 2 OL 120Vac L 1 Diode Check Run STBY Label Pin AC Voltage Readings for either pin 1 or pin 2 in STBY and RUN with one lead on Neutral of SK101 OL n a 2 OL 120Vac n a 1 Diode Check Run STBY Label Pin SK101 SMPS to AC IN SK102 SMPS to MASTER POWER SWITCH SK102 SK101 Bottom Right of SMPS Live Neutral With the Master Power Switch Closed On AC flows When Open Off...

Page 32: ...ormation General Backlight Information To Backlights Over 1 2KV Currently number of lamps Unknown To Backlights Over 1 2KV Ballast Section of SMPS EEFL External Electrode Fluorescent Lamp LOW COST Large number of lamps driven by a single inverter ...

Page 33: ...0 33 Simple structure Low price Complicated structure Simple structure Lamp manufacturing process Lamp assembly structure Low Cost Large number of Lamp Drive by single inverter EEFL Compared to CCFL EEFL Compared to CCFL ...

Page 34: ...Life Time For CCFL Hg gas is consumed mainly near the internal electrode For EEFL longer life time is expected because there is no internal electrode consuming Hg gas EEFL Bulb Design Compared to CCFL EEFL Bulb Design Compared to CCFL ...

Page 35: ...bruary 2009 42LH20 35 Ballast PWB Layout Ballast PWB Layout To Backlights Left Side T703 T704 Viewed from rear To Backlights Right Side SMPS PWB Backlights Test Point Bottom of R406 or R403 38V P P 1 2Kv ...

Page 36: ...V 24V On Back of PWB On Back of PWB INV On Off To Backlights 1 2Kv Two Transformers Drive Circuit FETs Q709 10 Drive Control Q702 R704 4 7KΩ R759 0Ω R714 100Ω GPIO 134 GPIO 136 R237 100Ω Q701 Q700 R703 R706 E5 7 8 9 10 7 8 9 10 STBY5V STBY5V L700 L733 Ballast Power Hot Gnd 390V P401 P402 Stand By 5V Reg Controller R717 3 3KΩ 5V General 160V 160V 42LH20 P700 Main Board to Power Supply P201 Ballast ...

Page 37: ...WM DIM manipulates the 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 ...

Page 38: ... from the Main Board easily measured at fuse F1 Diode LED1 is a boot up indicator and is helpful in troubleshooting as a quick indication 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 to the TFT panel CN3...

Page 39: ... 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 Position They would have been removed when removing the shield Be sure to reinstall them if servicing the T CON PWB ...

Page 40: ...ed 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 rock the cable out of the connector Shown by the arrows in Fig 3 Fig 3 CN5 LVDS UNLOCKING CN3 CN4 and CN5 UNLOCKING CN3 CN4 and CN5 The locking tab is flipped upward Press In Press In Pull Out CN3 or CN4 Locked T T CON Board Removal Continued C...

Page 41: ...February 2009 42LH20 41 LVDS Video and 12V from Main PWB T T CON Board With Shield CON Board With Shield ...

Page 42: ... TFT Drive PWB Shield Removed CON 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 D14 FL114 T CON p n EAT60663801 ...

Page 43: ...ght Blue Shortly 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 8V 3 3V 0V U10 Check the Regulator U10 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 ...

Page 44: ...February 2009 42LH20 44 T T CON TFT Drive Voltages for the Panel Checks CON TFT Drive Voltages for the Panel Checks 12V U7B 3 3V VCC 26V VGH_M Pin 8 16V VDD 5V VGL ...

Page 45: ...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 T CON TFT Driver Board CN3 and CN4 3 3V Voltage Check CON TFT Driver Board CN3 and CN4 3 3V Voltage Check ...

Page 46: ...S SEL 10 Gnd Gnd Gnd Gnd 9 Gnd Gnd Gnd Gnd 8 Gnd Gnd Gnd Gnd 7 Gnd Gnd Gnd Gnd 6 1 6V 12 1V 0V LVDS 12V 5 1 6V 12 1V 0V LVDS 12V 4 1 6V 12 1V 0V LVDS 12V 3 1 6V 12 1V 0V LVDS 12V 2 Gnd Gnd Gnd Gnd 1 Gnd Gnd Gnd Gnd 32 Gnd Gnd Gnd Gnd 31 Gnd Gnd Gnd Gnd 30 1 1V 3 1V 0V PWM DIM 29 Open 3 3V 0V OPC OUT 28 Gnd Gnd Gnd Gnd 27 1 1V 1 2V 0V TXA3 26 1 1V 1 2V 0V TXA3 25 Gnd Gnd Gnd Gnd 24 1 1V 1 2V 0V TXA...

Page 47: ...nt 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 Board Audio output signals to the Speakers Digital Audio Output Coaxial and Optical ON OFF Controls to the SMPS turning on low volt...

Page 48: ... two pieces 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 Flip the locking tabs upward pull the LVDS ribbon out 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 ...

Page 49: ...n P700 P801 P1204 IC100 Microprocessor and Video Processor X100 USB Tuner TU1001 To SMPS To Front PWB Assembly P801 to T CON PWB To Speakers Look carefully on top and behind the Video Processor IC for Chocolate Heat Transfer material Be sure to transfer to new PWB if replaced For Software Upgrade via Jig SW100 Reset X105 P600 LD1000 ...

Page 50: ...February 2009 42LH20 50 Main PWB Main PWB Back View Back View Voltages given on the 11X17 foldout Interconnect Diagram IC1003 IC1002 Tuner IC702 IC601 IC500 IC501 IC501 IC102 ...

Page 51: ...C704 3 3V FE 1 0 78V 2 Gnd 3 5V 4 7 4V 5 2 12V 6 3 28V 7 3 28 8 5V IC705 1 26V_VDDC 1 0 78V 2 Gnd 3 5V 4 5 9V 5 5V 6 1 3V 7 1 3V 8 3 16V IC701 1 8V_DDR 1 N C 2 3 18V 3 3 18V 4 5 N C 6 1 87V 7 0 8V 8 Gnd Q702 Inv On Control Gnd 0V 0 6V 3 85V 0V IC1000 1 2V_PVSB 1 N C 2 3 2 3 3 2V 4 5 N C 6 1 2V 7 0 8V 8 Gnd IC105 HDCP EEPROM 1 2 Gnd 3 5V 5 6 0V 4 7 Gnd 6 1 2V 7 0 8V 8 5V IC101 Flash Memory 1 2 0V 3...

Page 52: ...PWB X100 and X1005 Check Main PWB X100 and X1005 Check X1005 Location X100 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 ...

Page 53: ...n PWB LD1000 Function Main PWB LD1000 Function 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 ...

Page 54: ...February 2009 42LH20 54 Main PWB Tuner with Shield Off Pin ID Main PWB Tuner with Shield Off Pin ID 1 19 18 4 13 12 9 8 ...

Page 55: ... Video and SIF Output Check 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 ...

Page 56: ...09 42LH20 56 Main PWB Tuner Clock and Data Lines Main PWB Tuner Clock and Data Lines Pin 8 SDA 100uS 1V per div 5V p p Pin 9 SCL 100uS 1V per div 5V p p Note SCL and SDA only active during an actual Channel Change ...

Page 57: ...13 15 16 and 18 19 Pins 9 10 carry the clock These signals vary from each other but looking for signals like the ones shown below on any of these pins will confirm the output of video content This signal is using standard SMTE Color Bar 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 ...

Page 58: ...009 42LH20 58 Main PWB LVDS Connector P801 Pin Identification Main PWB LVDS Connector P801 Pin Identification 12V for T CON PWB PWM Dim Not used on T CON Video Video Video Video Clock Screen Size Video 30 1 P801 ...

Page 59: ...o T Main PWB Connector P801 to T CON Voltage and Diode Check CON Voltage and Diode Check Diode Mode values taken with all Connectors Removed Gnd Gnd 0V 0V Gnd 0V 0V Gnd 0V 0V Gnd 0V 0V Gnd Gnd SBY 1 1V 1 1V TXA1 15 Gnd Gnd Gnd 14 1 1V 1 2V TXA2 13 1 1V 1 1V TXA2 12 Gnd Gnd Gnd 11 1 1V 1 1V TXAC 10 1 1V 1 2V TXAC 9 Gnd Gnd Gnd 8 1 1V 1 2V TXA3 7 1 1V 1 2V TXA3 6 Gnd Gnd Gnd 5 Open 3 3V OPC OUT 4 1 ...

Page 60: ...V 5V 8 Gnd Gnd Gnd Gnd 6 Gnd Gnd Gnd Gnd 4 1 87V 4 98V 0V PWR ON 2 Diode Check Run STBY Label Pin nc nc nc nc 23 2V 1 7V 0V 1 A DIM 21 nc nc nc nc 19 Open 21 4V 0V 24V 17 Gnd Gnd Gnd Gnd 15 2 1V 12 3V 0V 12V 13 Gnd Gnd Gnd Gnd 11 1 1V 5 14V 5 14V 5V 9 1 1V 5 14V 5 14V 5V 7 Gnd Gnd Gnd Gnd 5 Gnd Gnd Gnd Gnd 3 nc nc nc nc 1 Diode Check Run STBY Label Pin 1 ADIM Pin 21 Fixed and not used 2 PDIM Pin 2...

Page 61: ...es taken with all Connectors Removed P1204 CONNECTOR MAIN PWB to P1 Front IR LED PWB Assy 2 17V 3 29V 0V POWER On Off 12 0 6V 3 29V 3 29V 3 3V_ST 11 Gnd Gnd Gnd Gnd 10 Open 4 8V 4 8V IR 9 Gnd Gnd Gnd Gnd 8 Gnd Gnd Gnd Gnd 7 1 13V 5 1V 5 1V 5V ST 6 1 08V 3 3V 3 3V Key2 5 1 08V 3 3V 3 3V Key1 4 Gnd Gnd Gnd Gnd 3 1 14V 3 3V 3 3V SDA 2 1 14V 3 3V 3 3V SCL 1 Diode Check Run STBY Label Pin ...

Page 62: ...ector P600 to Speakers Voltage and Diode Check Diode Mode values taken with all Connectors Removed SPK L SPK L SPK R SPK R LABEL 1 5V 10 7V 0V 4 1 5V 10 7V 0V 3 1 5V 10 7V 0V 2 1 5V 10 7V 0V 1 Diode Check Run SBY Pin P600 CONNECTOR Main to Speakers Use speaker out to test for defective Audio Amp IC600 ...

Page 63: ...FRONT IR BOARD FRONT IR BOARD To Side Key PWB The IR Sensor and Power LED control IC are located on the front of this Board Cover P1 P3 P1 To Main PWB c c c c Front IR and LED Control Assembly Layout Back View P3 Cover Removed ...

Page 64: ...February 2009 42LH20 64 IR Sensor POWER LEDS LED1 through LED10 Control IC U1 Power LEDs Front PWB Assembly IR and LED Control Layout Back View Front PWB Assembly IR and LED Control Layout Back View ...

Page 65: ...n Gnd 2 4V 2 4V Diode Check 3 3V 3 3V SCL 1 3 3V 3 3V SDA 2 Gnd Gnd Gnd 3 3 3V 3 3V Key1 4 3 3V 3 3V Key2 5 5 1V 5 1V 5V ST 6 Gnd Gnd Gnd 7 Gnd Gnd Gnd 8 4 8V 4 8V IR 9 Gnd Gnd Gnd 10 3 29V 3 29V 3 3V_ST 11 3 29V 0V POWER On Off 12 Run STBY LABEL Pin P1 Connector IR LED Control PWB to MAIN PWB P404 P3 Connector IR LED Control PWB to Side Key P3000 Gnd Key2 Gnd Key1 Label Gnd Open Gnd Open Diode Ch...

Page 66: ...February 2009 42LH20 66 KEY BOARD SECTION KEY BOARD SECTION To Main PWB P3000 SW3008 SW3007 SW3006 SW3005 SW3004 SW3003 SW3002 SW3001 c c ...

Page 67: ...hms 270 5 Ohms Pin 1 measured 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 Gnd Gnd 4 3 3V 3 3V 3 Gnd Gnd...

Page 68: ...BLY NOTES REASSEMBLY NOTES 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 of the post in the slot provided ...

Page 69: ...dout INTERCONNECT SECTION 11 X 17 Foldout This section shows the 11X17 foldout that This section shows the 11X17 foldout that s available in the Paper s available in the Paper and Adobe version of the Training Manual and Adobe version of the Training Manual ...

Page 70: ...OPC OUT 0V 3 3V Open 5 Gnd Gnd Gnd Gnd 6 TXA3 0V 1 2V 1 1V 7 TXA3 0V 1 2V 1 1V 8 Gnd Gnd Gnd Gnd 9 TXAC 0V 1 2V 1 1V 10 TXAC 0V 1 1V 1 1V 11 Gnd Gnd Gnd Gnd 12 TXA2 0V 1 1V 1 1V 13 TXA2 0V 1 2V 1 1V 14 Gnd Gnd Gnd Gnd 15 TXA1 Gnd 1 1V 1 1V Pin LABEL SBY Run Diode Check 16 TXA1 0V 1 2V 1 1V 17 Gnd Gnd Gnd Gnd 18 TXA0 0V 1 1V 0 8V 19 TXA0 0V 1 2V 1 1V 20 Gnd Gnd Gnd Gnd 21 OPC EN 0V 0V 1 1V 22 LVDS ...

Page 71: ...ken using NTSC Color Bar RF input LVDS P801 PIN 4 OPC Out LVDS P801 PIN 6 TXA3 LVDS P801 PIN 7 TXA3 LVDS P801 PIN 9 TXAC LVDS P801 PIN 10 TXAC LVDS P801 PIN 12 TXA2 LVDS P801 PIN 13 TXA2 LVDS P801 PIN 15 TXA1 LVDS P801 PIN 16 TXA1 LVDS P801 PIN 18 TXA0 LVDS P801 PIN 19 TXA0 ...

Page 72: ...04 3 3V FE 1 0 78V 2 Gnd 3 5V 4 7 4V 5 2 12V 6 3 28V 7 3 28 8 5V IC705 1 26V_VDDC 1 0 78V 2 Gnd 3 5V 4 5 9V 5 5V 6 1 3V 7 1 3V 8 3 16V IC701 1 8V_DDR 1 N C 2 3 18V 3 3 18V 4 5 N C 6 1 87V 7 0 8V 8 Gnd Q702 Inv On Control Gnd 0V 0 6V 3 85V 0V IC1000 1 2V_PVSB 1 N C 2 3 2 3 3 2V 4 5 N C 6 1 2V 7 0 8V 8 Gnd IC105 HDCP EEPROM 1 2 Gnd 3 5V 5 6 0V 4 7 Gnd 6 1 2V 7 0 8V 8 5V IC101 Flash Memory 1 2 0V 3 4...

Page 73: ... Board Rear View Component Layout 42LH20 Main Board Rear View Component Layout IC500 IC501 HDMI EDID IC500 IC501 IC1200 R G B PC DDC IC102 NAN Flash Memory 1 4 Gnd 5 4 82V 6 4 82V 7 4 82V 8 4 82V IC501 IC501 1 4 Gnd 5 4 82V 6 4 82V 7 4 82V 8 4 82V IC1200 1 4 Gnd 5 4 82V 6 4 82V 7 4 82V 8 4 82V Audio Mute Switch B 0 08V C 3 26V E Gnd B C E Q600 IC103 1 2 3 IC103 Reset Gen 1 Gnd 2 3 26V 3 3 26V Q600...

Page 74: ...42LH20 42LH20 This concludes the 42LH20 training session Direct View LCD ...

Search results

Summary of Contents for 42LH20 Series

Reviews:

Related manuals for 42LH20 Series

Brands by name

Popular brands

LG 42LH20 Series, Service Manual

Search results

Summary of Contents for 42LH20 Series

Reviews:

Related manuals for 42LH20 Series

Brands by name

Popular brands