LED TV Service Manual - Chassis UAX2A - Model 49NANO85UNA

Oct 23, 2026

Service manual for an LG LED TV chassis UAX2A, model 49NANO85UNA, providing safety and servicing precautions required before any maintenance. It defines special safety-related components and replacement requirements to prevent shock, fire, or other hazards, plus general servicing rules for unplugging, correct electrolytic capacitor polarity, and safe high-voltage measurement. It also specifies AC leakage current cold and hot check methods with resistance/voltage limits to ensure exposed metallic parts remain safe for customer operation.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages71

Reading Time2 h 59 min

AccessFree to download

Contents

Safety Precautions

Servicing Precautions

Specification

Software Update

Block Diagram

Exploded View

Assembly / Disassembly Guide

Troubleshooting Guide

LED TV SERVICE MANUAL CHASSIS : UAX2A MODEL : 49NANO85UNA CAUTION BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. P/NO : MFL71703901 (2001-REV00) Any reproduction, duplication, distribution (including by way of email, facsimile or other electronic means), publication, modification, copying or transmission of this Service Manual is STRICTLY PROHIBITED unless you have obtained the prior written consent of the LG Electronics entity from which you received this Service Manual. The material covered by this prohibition includes, without limitation, any text, graphics or logos in this Service Manual. Copyright © 2020 LG Electronics Inc. All rights reserved. Only training and service purposes. CONTENTS CONTENTS .............................................................................................. 2 SAFETY PRECAUTIONS ........................................................................ 3 SERVICING PRECAUTIONS ................................................................... 4 SPECIFICATION ....................................................................................... 6 SOFTWARE UPDATE ............................................................................. 9 BLOCK DIAGRAM ................................................................................. 10 EXPLODED VIEW .................................................................................. 11 ASSEMBLY / DISASSEMBLY GUIDE ................................................... 12 TROUBLE SHOOTING GUIDE ................................................ APPENDIX -2- Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes. SAFETY PRECAUTIONS IMPORTANT SAFETY NOTICE Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in the Exploded View. It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent Shock, Fire, or other Hazards. Do not modify the original design without permission of manufacturer. General Guidance An isolation Transformer should always be used during the servicing of a receiver whose chassis is not isolated from the AC power line. Use a transformer of adequate power rating as this protects the technician from accidents resulting in personal injury from electrical shocks. It will also protect the receiver and it's components from being damaged by accidental shorts of the circuitry that may be inadvertently introduced during the service operation. If any fuse (or Fusible Resistor) in this TV receiver is blown, replace it with the specified. When replacing a high wattage resistor (Oxide Metal Film Resistor, over 1 W), keep the resistor 10 mm away from PCB. Keep wires away from high voltage or high temperature parts. Before returning the receiver to the customer, always perform an AC leakage current check on the exposed metallic parts of the cabinet, such as antennas, terminals, etc. , tobe sure the set is safe to operate without damage of electrical shock. Leakage Current Cold Check(Antenna Cold Check) With the instrument AC plug removed from AC source, connect an electrical jumper across the two AC plug prongs. Place the AC switch in the on position, connect one lead of ohm-meter to the AC plug prongs tied together and touch other ohm-meter lead in turn to each exposed metallic parts such as antenna terminals, phone jacks, etc. If the exposed metallic part has a return path to the chassis, the measured resistance should be between 1 MΩ and 5.2 MΩ . When the exposed metal has no return path to the chassis the reading must be infinite. An other abnormality exists that must be corrected before the receiver is returned to the customer. Leakage Current Hot Check (See below Figure) Plug the AC cord directly into the AC outlet. Do not use a line Isolation Trans

FAQs

What safety precautions must be read before servicing the chassis?

Before servicing, read and follow the SAFETY PRECAUTIONS in the manual (page 3). The document emphasizes safety first and replacing special safety-related parts as recommended.

How should the technician handle electrical safety checks during servicing?

Use an isolation transformer when the chassis is not isolated from the AC power line. Perform AC leakage current cold check and hot check on exposed metallic parts before returning the receiver to the customer.

What are the key limits for the leakage current hot check?

The measured voltage across the specified resistor must not exceed 0.75 volt RMS, corresponding to 0.5 mA. If measurements are out of limits, the set must be checked and repaired before return.

Oct 23, 2026

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