LG 37LD450 Service Manual

The LG 37LD450 is a 37-inch LCD HDTV featuring Full HD 1080p resolution, built-in digital/analog tuner, multiple HDMI inputs, USB connectivity, Intelligent Sensor technology for automatic picture optimization, Clear Voice II for enhanced dialogue clarity, and Energy Star compliance. This service manual provides technical information for service personnel including disassembly instructions, circuit diagrams, troubleshooting procedures, and replacement part information.

1. Product Specifications 2. Safety Precautions 3. Disassembly Instructions 4. Circuit Diagrams 5. Block Diagrams 6. Troubleshooting Flowcharts 7. Waveform Measurements 8. Replacement Parts List 9. Adjustment Procedures 10. Software Update Instructions 11. Service Mode Access

Product Specifications

Technical specifications and performance characteristics of the LG 37LD450 LCD TV.

SpecificationDetails
Display Size37-inch LCD Panel
Resolution1920 x 1080 (Full HD)
Brightness500 cd/m²
Contrast Ratio100,000:1 (Dynamic)
Response Time5ms
Viewing Angle178°/178°
TunerATSC/NTSC/Clear QAM
Inputs3x HDMI, 2x Component, 1x Composite, 1x PC Input, 1x USB
Audio Output10W + 10W
Power Consumption85W (Typical)

Safety Precautions

Important safety instructions for service personnel during repair and maintenance procedures.

  1. Always disconnect AC power before disassembling the unit.
  2. Use proper grounding procedures when handling circuit boards.
  3. Handle LCD panel with care to avoid breakage and electrical shock.
  4. Discharge capacitors before working on power supply section.
  5. Use approved replacement parts only.

WARNING! High voltage present in power supply and inverter sections. Use extreme caution when servicing.

Disassembly Instructions

Step-by-step procedure for disassembling the LG 37LD450 LCD TV.

  1. Remove stand: Lay TV face down on soft surface, remove screws securing stand.
  2. Remove rear cover: Remove all screws from rear casing, carefully separate front and rear covers.
  3. Disconnect cables: Note cable positions before disconnecting main board, power supply, and control board connections.
  4. Remove main board: Remove mounting screws and carefully lift main board assembly.
  5. Access LCD panel: Remove metal shield and bezel to access LCD panel and backlight assembly.

CAUTION! Handle LCD panel edges only. Avoid pressure on screen surface.

Circuit Diagrams

Complete schematic diagrams for all major circuit sections.

Block Diagrams

System block diagrams showing signal flow and interconnections between boards.

Main System: Digital tuner → Main processor → Scaler → T-Con → LCD panel

Audio Path: Audio inputs → Audio processor → Amplifier → Speakers

Power Distribution: AC input → Power supply → Main board → Inverter → Backlights

Troubleshooting Flowcharts

Systematic troubleshooting procedures for common failure symptoms.

SymptomCheck SequenceTest Points
No PowerAC input → Fuse → Standby voltage → Main power supplyTP201 (5VSTBY), TP202 (12V)
No BacklightInverter power → Backlight enable → CCFL connectionsCN201 (24V), BL_ON signal
No PictureLVDS signal → T-Con voltages → Panel voltagesLVDS connector, VGH, VGL
No SoundAudio input → Audio processor → Amplifier ICIC601 input/output, speaker connections
No TunerTuner power → IF signal → Demodulator ICTuner 5V, SDA/SCL lines

Waveform Measurements

Critical waveform measurements and expected values at key test points.

  1. Power Supply: Check ripple on 12V and 24V outputs (should be less than 100mV p-p).
  2. Backlight Inverter: Measure CCFL drive waveform frequency and amplitude.
  3. LVDS Signal: Verify proper LVDS data and clock signals to T-Con board.
  4. Audio Output: Check for clipping and distortion at amplifier output.
  5. Clock Circuits: Verify crystal oscillator frequencies on main processor.

Tip: Use 100MHz oscilloscope for accurate waveform measurements.

Replacement Parts List

Authorized replacement parts with LG part numbers and descriptions.

Part NumberDescriptionBoard Location
EAX36129801Power Supply Board AssemblyPSU
EAX36134701Main Board AssemblyMain
EAX36134702T-Con Board AssemblyT-Con
6871QDH011ALCD Panel CompletePanel
LGAC34924001Remote ControlAccessory
IC801Main ProcessorMain Board
Q201-Q204Power MOSFETsPower Supply

Adjustment Procedures

Factory adjustment procedures for picture quality and system parameters.

  1. White Balance: Access service menu, adjust R/G/B gain and cutoff values.
  2. Geometry: Adjust horizontal/vertical position and size parameters.
  3. Color Temperature: Set to 6500K using color analyzer.
  4. Backlight Level: Adjust inverter output for uniform brightness.
  5. Audio Levels: Balance left/right channels and set maximum output level.

WARNING! Record original values before making adjustments. Incorrect settings may degrade performance.

Software Update Instructions

Procedures for updating TV firmware and software.

USB Update Method:

  1. Download latest firmware from LG service website.
  2. Extract files to USB drive root directory.
  3. Insert USB drive into TV USB port.
  4. Enter service menu and select USB update option.
  5. Do not power off during update process (approximately 5 minutes).

Service Mode Access

Methods for accessing service menu and engineering modes.

ModeAccess MethodFunction
Service MenuMenu + 0000 on remoteBasic adjustments and settings
Engineering MenuMenu + 0413 on remoteAdvanced factory settings
In-Service MenuVolume + Menu on TV buttonsQuick service adjustments
Burn-in TestPower + Menu on TV buttonsPanel testing mode

Reset: Service Menu > Option > Reset to return to factory defaults.

Service Support: LG Service Network: 1-800-243-0000

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