LG 42LG70 Training Manual
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LG 42LG70 Training Manual

LG 42LG70 Training Manual

Direct view lcd
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42LG70
42LG70
Direct View LCD

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Summary of Contents for LG 42LG70

  • Page 1 42LG70 42LG70 Direct View LCD...
  • Page 2 LCD Overview, General Troubleshooting Steps, Signal Distribution, Disassembly Instructions and Voltages Section 2 Circuit Board Operation, Troubleshooting of : • Switch mode Power Supply • Ballast Board • Main Board • T-CON Board • Ft Control Board Spring 2009 LCD DV 42LG70...

  • Page 3: Overview Of Topics To Be Discussed

    Overview of Topics to be Discussed Overview of Topics to be Discussed 42LG70 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.

  • Page 4: Preliminary Matters (The Fine Print)

    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.

  • Page 5: Esd Notice

    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. Spring 2009 LCD DV 42LG70...

  • Page 6: Contact Information

    USA Website (GCSC) aic.lgservice.com Customer Service Website us.lgservice.com LG CS Academy lgcsacademy.com LG Web Training lge.webex.com Published March 2009 by LG Technical Support and Training LG Electronics Alabama, Inc. 201 James Record Road, Huntsville, AL, 35813. Spring 2009 LCD DV 42LG70...

  • Page 7: Section 1: Lcd Overview

    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… Spring 2009 LCD DV 42LG70...

  • Page 8: Basic Troubleshooting Steps

    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. Spring 2009 LCD DV 42LG70...
  • Page 9 42LG70 Product Information 42LG70 Product Information This section of the manual will discuss the specifications of the 42LG70 LCD Direct View Display Panel. Spring 2009 LCD DV 42LG70...
  • Page 10 • 4x HDMI™ V.1.3 with Deep Color • Intelligent Sensor • 24p Real Cinema • AV Mode (Cinema, Sports, Game) • Clear Voice • LG SimpLink™ Connectivity • Invisible Speaker System • USB 2.0 (JPEG, MP3) • ISFccc Spring 2009...

  • Page 11: Basic Specifications (Logo Familiarization)

    Intelligent Sensor Unlike other sensors which can only sense brightness of ambient light, LG’s “Intelligent Sensor” uses 4,096 sensing steps to evaluate its surroundings. Using a sophisticated algorithm, the LG processes picture quality elements including brightness, contrast, color, sharpness and white balance.
  • Page 12 SIMPLINK Allows for convenient control of other LG SimpLink products using the existing HDMI connection. Invisible Speaker System A new invisible speaker system tuned by renowned audio expert, Mr. Mark Levinson.

  • Page 13: Remote Control Familiarization

    Remote Control Familiarization Remote Control Familiarization BOTTOM PORTION TOP PORTION Spring 2009 LCD DV 42LG70...
  • Page 14 4) The Service Menu appears Note: It is possible, dependant upon the Software Version, a Password may be required to enter the Service Menu. If a password is required, enter 0000 Spring 2009 LCD DV 42LG70...

  • Page 15: Rear And Side Input Jacks

    Rear and Side Input Jacks Rear and Side Input Jacks Rear Input Jacks Side Input Jacks Main PWB Orientation Spring 2009 LCD DV 42LG70...

  • Page 16: 42Lg70 Product Dimensions

    42LG70 Product Dimensions 42LG70 Product Dimensions Spring 2009 LCD DV 42LG70...

  • Page 17: Disassembly Section

    DISASSEMBLY SECTION This section of the manual will discuss Disassembly, Layout and Circuit Board Identification, of the 42LG70 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.
  • Page 18 The Stand does not need to be removed Remove the 16 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. Spring 2009 LCD DV 42LG70...
  • Page 19 Power Supply PWB Removal Power Supply PWB Removal P201 Disconnect P201, AC In and P204. Remove the 4 screws indicated by the arrows. Spring 2009 LCD DV 42LG70...
  • Page 20 Remove the plastic piece. Remove the 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. Spring 2009 LCD DV 42LG70...
  • Page 21 P404 removal process. NOTE: Look carefully on top and behind the BCM and Micronas IC. Look for a piece of Chocolate (Heat Transfer Material). Be sure to transfer to new PWB if replaced. P501 Spring 2009 LCD DV 42LG70...
  • Page 22 Lift up the left bracket and work the They would already be removed in the shield out and off. previous step. Disconnect CN1, CN2, CN4 and CN5. See next slide for details. Remove and save the tape over the LVDS Cables Spring 2009 LCD DV 42LG70...
  • Page 23 Then the flex cable can be easily removed. CN2; Press in on the two tabs and slowly Unlocked rock the cable out of the connector. Fig 2 (Shown by the arrows in Fig 3) The locking tab is flipped upward Spring 2009 LCD DV 42LG70...

  • Page 24: Troubleshooting Section

    TROUBLESHOOTING SECTION TROUBLESHOOTING SECTION This section of the manual will discuss troubleshooting. Upon completion of this section the Technician will have a better understanding of how to diagnosis and resolve problems. Spring 2009 LCD DV 42LG70...

  • Page 25: Circuit Board Layout

    T-CON Under Shield To Left Side LVDS Cables POWER SUPPLY Ballast Under Main “Digital” Shield Under Shield Input Backlight Side Inputs Connection To Right Side Rear Inputs Tweeter AC Input Tweeter Side Woofer Woofer Ft Control Controls Spring 2009 LCD DV 42LG70...

  • Page 26: Power Supply (Smps) Pwb Layout

    Power Supply (SMPS) PWB Layout Power Supply (SMPS) PWB Layout Hot Ground Shock Hazard To Main P201 Not used AC IN F100 6.3A/250V AC IN F101 3.15A/250V Run 385.7V Stby 155.8V From Hot Gnd P204 To Ballast Spring 2009 LCD DV 42LG70...
  • Page 27 Power Power Supply Supply turn on turn on sequence sequence from from Micro Micro Processor Processor Spring 2009 LCD DV 42LG70...

  • Page 28: Power Supply Controls From Micro Processor

    Power Supply Power Supply Controls from Controls from Micro Processor Micro Processor Spring 2009 LCD DV 42LG70...
  • Page 29 24 Volt Supply. Confirm Pin 12 of P204 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. Spring 2009 LCD DV 42LG70...

  • Page 30: Test 1 Power Supply Pwb Low Voltage Test

    P201 (16V pins 1 and 2) (12V pins 5 and 6) b) Check that the 24V on P204 pins 1~5 (Ballast Voltage) is turned on. (3) Remove AC power. Reinsert the plug P204 to the ballast. Spring 2009 LCD DV 42LG70...
  • Page 31 NOTE: Pin 11 and 12 on P204 or Pin 12 and 13 on P201 (ADIM/PDIM) must be above 1V or the backlights will be extremely dim. This is controlled by the Customer’s OSD settings. 0% (0.9V) to 100% (3.3V). Manipulated by the BCM Chip. (Video Processor) Spring 2009 LCD DV 42LG70...
  • Page 32 PDIM Pin 22 can vary according to type of signal being processed, OSD Backlight setting. 0.9V 0% to 3.3V 100% and the Intelligent Sensor. Output from the BCM chip. Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 33 PWM-DIM (PDIM Pin 22) can vary according to type of signal being processed, OSD Backlight setting. 0.9V 0% to 3.3V 100% and the Intelligent Sensor. Output from the BCM chip. Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 34 General Backlight Information General Backlight Information Ballast To Backlights Over 1.2KV To Backlights Over 1.2KV Currently, number of lamps “Unknown” EEFL (External Electrode Fluorescent Lamp) LOW COST Large number of lamps driven by a single inverter Spring 2009 LCD DV 42LG70...
  • Page 35 EEFL (External Electrode Fluorescent Lamp) CCFL (Cold Cathode Fluorescent Lamp) Stating Voltage Starting & Operating Voltage Operating Voltage Complicated structure Simple structure Low Cost Lamp manufacturing process Large number of Lamp Lamp assembly structure Drive by single inverter Spring 2009 LCD DV 42LG70...
  • Page 36 EEFL (External Electrode Fluorescent Lamp) External electrode Phosphor : Hg : electron 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 Spring 2009 LCD DV 42LG70...
  • Page 37 Ballast PWB Layout Ballast PWB Layout BALLAST p/n EAY56798701 To Backlights Left Side To Backlights Right Side MCN1 To Power Supply Protects 24V 15A/65V Spring 2009 LCD DV 42LG70...
  • Page 38 Ballast PWB Transformer Check Ballast PWB Transformer Check ANY TRANSFORMER PRIMARY Caution: Over 1.2kV SIDE WAVEFORM CHECK 1V p/div 5us p/div 5V p/p 2 3 4 5 1V p/div 5us p/div 4.3V p/p Spring 2009 LCD DV 42LG70...
  • Page 39 Ballast Control Signals Circuit Diagram Ballast Control Signals Circuit Diagram Spring 2009 LCD DV 42LG70...
  • Page 40 Power Supply Backlight Drive Signal Effects Power Supply Backlight Drive Signal Effects VBR-B PWMDIM manipulates the Burst Triangle Oscillator in the ballast drive IC. VBR-A BR1 (ADIM) also manipulates the Burst Triangle Oscillator But it is not used. Spring 2009 LCD DV 42LG70...
  • Page 41 Noise Dampening Pads) RF NOISE DAMPENING AND HEAT TRANSFER MATERIAL PADS. MAKE SURE TO SAVE THESE IF REPLACING THE BALLAST. There is a white box outlined on the PWB silk screen indicating where the Chocolate goes. Spring 2009 LCD DV 42LG70...
  • Page 42 THE BALLAST. BALLAST MAKE SURE THEY ARE SHIELD PLACED IN THE CORRECT LOCATION BEFORE REINSTALLING THE Insulates and Heat SHIELD. Transfer for Q7, Q8, Q9 and Q10 Insulates and Heat Transfer for T3 and T4 Spring 2009 LCD DV 42LG70...
  • Page 43 VBR-A Pin 11 Fixed and not used VBR-B Pin 13 can vary according to type of signal being processed, OSD Backlight setting. 0.9V 0% to 3.3V 100% and the Intelligent Sensor. Output from the BCM chip. Spring 2009 LCD DV 42LG70...
  • Page 44 ( easily measured at fuse F1). Diode LD1 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. LG Philips LCD Drive IC Next 2 Slide...
  • Page 45 CON (TFT DRIVE) PWB WITH SHIELD CON (TFT DRIVE) PWB WITH SHIELD Two LVDS feeds from Main PWB Spring 2009 LCD DV 42LG70...

  • Page 46: T - Con (Tft Drive) Pwb (Shield Removed)

    CON (TFT Drive) PWB (Shield Removed) CON (TFT Drive) PWB (Shield Removed) T-CON p/n EAT56803001 To TFT Panel To TFT Panel Remember to replace screws for ground purposes if turning on the set is required. Control Spring 2009 LCD DV 42LG70...

  • Page 47: T - Con (Tft Drive) Pwb Checks

    Check Fuse backlights illuminate if all is OK. F1 for 12V Power Off Power 1 Power On Anode 0V Anode 11.6V Anode 11.6V Cathode 0V Cathode 0V Cathode 9.5V LED OFF LED ON LED OFF Spring 2009 LCD DV 42LG70...

  • Page 48: Input Signal Processing

    • Quadruple 12 Bit LVDS 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 voltage generation and Backlights • Backlight intensitiy control signals Spring 2009 LCD DV 42LG70...
  • Page 49 24 frames per second system used for recording, the picture develops visual artifacts when converted to 60 frames per second. 3:2 Pull Down was developed to eliminate this problem. Frame Rate Conversion (Real Cinema) eliminates the need for 3:2 Pull Down. Spring 2009 LCD DV 42LG70...

  • Page 50: Trumotion 120Hz ( Vector Based Motion Compensation)

    TruMotion 120 Hz can reduce blurring on fast moving scenes. TruMotion carefully analyses the picture signal by using advanced algorithms to automatically calculate a new image frame between each original frame (MEDI). Conventional (60Hz) Conventional True Motion (120Hz) Spring 2009 LCD DV 42LG70...
  • Page 51 Frame Rate Conversion eliminates the need for 3:2 Pull Down Conversion An irregular sequence of frames in a movie or video Time image 1/24[sec] (Film) 1/60[sec] Judder Judder Conventional (60Hz) 1/120[sec] TruCinema (120Hz) Scene A Scene B Scene C Spring 2009 LCD DV 42LG70...
  • Page 52 Look carefully on top and behind the BCM IC and If video returns Micronas IC for to normal, PWB Chocolate (Heat Transfer) needs to be material. replaced. Be sure to transfer to new PWB if replaced. P501 Speakers Spring 2009 LCD DV 42LG70...
  • Page 53 Main PWB Main PWB (Back View) (Back View) Voltages given on the 11X17 foldout “Interconnect Diagram” Spring 2009 LCD DV 42LG70...
  • Page 54 STBY Label Q901 STBY Label Function: 5V-TU Regulator Function: Turns on Q900 LVDS Switch Pin 1 Input 0.7V LVDS-Panel-Control Pin 2 3.3V On/Off Power-CTL 3.3V On low/Off hi Pin 3 Output Pin 4 Pin 5 Spring 2009 LCD DV 42LG70...
  • Page 55 Pull Up Pin 7 Pin 14 3.3V B+ for IC +3.3V Pin 5 3.3V 3.3V Pin 8 4.8V Pins 8,9,10,11,12,13 not used Pin 6 3.3V 3.3V Pin 7 Write Protect Pin 8 3.3V 3.3V 3.3VST-Micom Spring 2009 LCD DV 42LG70...
  • Page 56 On/Off Power-CTL 2.6V Pin 5 Pins 1,2 Pin 3 Pin 6 Pins 3,4 Pin 4 3.3V Pin 7 Pin 5 Pin 5 Output Pin 8 1.3V Pin 6 4.7V Pin 7 Write Protect Pin 8 4.73V Vcc+5V Spring 2009 LCD DV 42LG70...
  • Page 57 Pin 5 Pin 3 1.2V Output IC1007 STBY Pin 4 Pin 1 3.3V Pin 5 3.3V On/Off Power-CTL Pin 2 3.3V Pin 6 1.2V Pin 3 Pin 7 COMP Pin 4 Pin 8 Pin 5 2.5V Spring 2009 LCD DV 42LG70...
  • Page 58 Set on or off X400 Only when set is on Micronas Crystal X200 780mVp/p 54Mhz X1000 Location X400 Location X200 Location Only when set is on Use bottom Video Processor MAIN PWB (BCM) Crystal of L206 Spring 2009 LCD DV 42LG70...
  • Page 59 If LD803 is illuminated GREEN, +3.3V is OK. Main PWB LD803 Location MAIN PWB Note: Only ½ of the dual LED is used. Circuit turning on LD803 shown on next slide Circuit turning on LD803 shown on next slide Spring 2009 LCD DV 42LG70...
  • Page 60 Main PWB LD803 Circuit Details Main PWB LD803 Circuit Details Spring 2009 LCD DV 42LG70...
  • Page 61 If you leave the shield on you can still access the same pins. Be careful not to accidentally ground out your test lead on the shield. (Note: This is a picture from a different model, but the concept is the same) Spring 2009 LCD DV 42LG70...
  • Page 62 Main PWB Tuner Video and Output Check Main PWB Tuner Video and Output Check USING SMTE COLOR BAR SIGNAL INPUT Pin 14 “SIF” Signal 850mVp/p 20nSec rate Pin 16 “Video” Signal 1Vp/p 20uSec rate Tuner Location MAIN PWB Spring 2009 LCD DV 42LG70...
  • Page 63 This signal is using standard SMTE Color Bar output from a generator as the input source. P1000 Location Pin 11 500us Main PWB LD803 Location This is just a sample Pin 16 of two pins on the LVDS. 500us There are 24 pins on P1000 carrying video. Spring 2009 LCD DV 42LG70...
  • Page 64 This signal is using standard SMTE Color Bar output from a generator as the input source. P1001 Location Pin 1 500us MAIN PWB This is just a sample of Pin 15 two pins on the LVDS. There are 24 pins on 500us P1001 carrying video. Spring 2009 LCD DV 42LG70...
  • Page 65 Diode Check 12.3V 3.1V ST-5V ST-5V 5.1V 1.48V ST-5V ST-5V 5.1V 1.48V 5V-MNT 2.86V RL-ON 2.8V *PWM-VBRA 1.7V Pin 21 PWM-VBRA (ADIM) Is Fixed and is not used Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 66 Pin 22 PWM-VBRB (VBR-B) can vary according to type of signal being processed, OSD Backlight setting. (0.9V 0% to 3.3V 100%) and the Intelligent Sensor. Output from the BCM chip. Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 67 1.13V 1.27V 1.14V 1.27V 1.14V 1.27V LVDS-SEL 0.5V 3.3V 0.66V 1.4V 1.2V 1.4V 1.2V Video Signal Pins 1.3V 1.2V 1.2V 1.2V Diode Mode values taken 1.4V 1.2V with all Connectors 1.4V 1.2V Removed AFLC-EN 3.3V Spring 2009 LCD DV 42LG70...
  • Page 68 1.27V Video Signal Pins 1.3V 1.27V 1.2V 1.27V 1.2V 1.27V LVDS-SEL 1.2V 1.2V 1.1V 1.2V Video Signal Pins 1.1V 1.2V 1.2V 1.2V Diode Mode values taken 1.1V 1.2V with all Connectors Removed 1.1V 1.2V AFLC-EN Spring 2009 LCD DV 42LG70...
  • Page 69 1.3V 1.27V 1.3V 1.27V 1.1V 1.27V 1.3V 1.27V 1.1V 1.27V 1.3V 1.27V Pins identified in Bold Blue are used to send video content to the T-CON PWB. Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 70 3.3V 2.13V EYEQ-SDA 3.3V 3.3V 2.13V Key1 3.3V 3.3V 1.77V Key2 3.3V 3.3V 1.77V 3.3V 3.3V 0.55V 5V ST 1.48V Ready 3.9V 3.9V 1.24V EYEQ-Reset Ready PWB-Buzz Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 71 Main PWB Connector P501 Voltage and Resistance P501 CONNECTOR "Main" to "Speakers" Diode Check 2.58V 2.58V 2.58V 2.58V Use speaker out to test for defective Audio Amp IC501 Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 72 Front PWB Assembly Layout The Touch Sensitive Power Switch, Intelligent Sensor and IR Sensor are located on the front of this PWB Light Diffuser for the Intelligent Sensor IR Sensor To Side Key Control PWB To Main PWB Spring 2009 LCD DV 42LG70...
  • Page 73 Front PWB Assembly (Front View) Layout Front PWB Assembly (Front View) Layout Sensor Close Up Light Diffuser for the Intelligent Sensor 3 Sensors POWER LED IR Sensor Spring 2009 LCD DV 42LG70...
  • Page 74 J3 from Ft Control to Side STBY Diode Check Key P100 3.25V 3.25V STBY 3.25V 3.25V 3.3V 3.3V 3.3V 3.3V 3.3V 3.3V 3.3V 3.3V 3.3V 0.1V 0.1V 1.8V 5.1V 5.1V 3.92V 3.92V Diode Mode values taken with all Connectors Removed Spring 2009 LCD DV 42LG70...
  • Page 75 This section shows the 11X17 foldout that ’ s available in the Paper This section shows the 11X17 foldout that ’ s available in the Paper and Adobe version of the Training Manual. and Adobe version of the Training Manual. Spring 2009 LCD DV 42LG70...
  • Page 76 42LG70 INTERCONNECT DIAGRAM P201 Odd "SMPS" to P800 "Main PWB" P201 Even "SMPS" to P800 "Main PWB" Any Transformer on Ballast P204 "SMPS" to MCN1 "Ballast PWB" TO TFT MODULE Label STBY Diode Check Label STBY Diode Check Label STBY Diode Check 16.5V...
  • Page 77 REGULATORS/ICs ON FRONT IC405 STBY Label Q400 STBY Label Function: Micro Reset control Function: Reset to Micro Pins 1 3.3V Input 3.3VST-Micom 0.59V 0.59V Input from IC405 Pins 2 Hi-Lo to IC407 pin 4 Pins 3 Hi then Lo to Q400 IC803 STBY Q900...
  • Page 78 42LG70 LVDS P1000 WAVEFORMS 42LG70 P1000 LVDS CABLE WAVEFORMS: Waveforms taken using SMTP Color Bar input. All readings give the Scale 10mV and Time Base related to scope settings. Top waveform in each image gives a slower rate, 2us per division. Outlined area is shown in the bottom waveform at 500ns per division time base.
  • Page 79 42LG70 LVDS P1001 WAVEFORMS 42LG70 P1001 LVDS CABLE WAVEFORMS: Waveforms taken using SMTP Color Bar input. All readings give the Scale 10mV and Time Base related to scope settings. Top waveform in each image gives a slower rate, 2us per division. Outlined area is shown in the bottom waveform at 500ns per division time base.
  • Page 80 42LG70 42LG70 Direct View LCD This concludes the 42LG70 training session.

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