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LG CM7420 User Manual

LG CM7420
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Mini Hi-Fi System
SERVICE MANUAL
MODEL: CM7420
(CM7420, CMS7520F)
CAUTION
BEFORE SERVICING THE UNIT, READ THE “SAFETY PRECAUTIONS”
IN THIS MANUAL.
MODEL: CM7420 (CM4520, CMS7520F)SERVICE MANUAL
2102 ,JULY75814469NFA : ON/P
Website http://biz.lgservice.com
Internal Use Only
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LG CM7420 Specifications

General IconGeneral
KaraokeNo
Bass reflex-
Speaker type4-way
Subwoofer typePassive subwoofer
RMS rated power650 W
Number of speakers2
Subwoofer includedYes
Peak Music Power Output (PMPO)7200 W
TypeHome audio mini system
Product colorBlack
Playback disc formatsCD audio
Audio formats supportedMP3
Apple docking compatibilityNot supported
Power sourceAC

Summary

SECTION 1 SUMMARY

SERVICING PRECAUTIONS

Precautions for handling the pick-up unit and general servicing.

ESD PRECAUTIONS

Precautions for handling electrostatic sensitive devices (ESD).

HIDDEN KEY MODE

Special modes accessible via hidden key combinations.

SERVICE INFORMATION FOR EEPROM

Procedures for accessing and managing EEPROM data.

PROGRAM DOWNLOAD GUIDE

Instructions for downloading firmware or software updates.

SPECIFICATIONS

Technical specifications of the Mini Hi-Fi System.

SECTION 2 CABINET & MAIN CHASSIS

EXPLODED VIEWS

Visual diagrams showing the assembly of the unit's components.

SECTION 3 ELECTRICAL

TRAINING MASTER

Troubleshooting guide for common sound issues.

ONE POINT REPAIR GUIDE

Specific repair procedures for common faults.

ELECTRICAL TROUBLESHOOTING GUIDE

Systematic troubleshooting steps for electrical problems.

WAVEFORMS

Reference waveforms for diagnosing servo and motor issues.

WIRING DIAGRAM

Diagram illustrating the electrical connections between components.

MAIN SYSTEM BLOCK DIAGRAM

Block diagram of the main system architecture.

SMPS BLOCK DIAGRAM

Block diagram of the Switched-Mode Power Supply.

SMPS CIRCUIT DIAGRAM

Detailed schematic of the power supply unit's circuit.

MAIN - MICOM CIRCUIT DIAGRAM

Circuit diagram for the main microcontroller unit.

MAIN - PWM / FILTER CIRCUIT DIAGRAM

Circuit diagram for PWM and filter sections.

MAIN - IR AMP CIRCUIT DIAGRAM

Circuit diagram for the IR amplifier.

MAIN - DSP / USB / IPOD CIRCUIT DIAGRAM

Circuit diagram for DSP, USB, and iPod functions.

MAIN - RF SERVO CIRCUIT DIAGRAM

Circuit diagram for RF and servo systems.

MAIN - ADC CIRCUIT DIAGRAM

Circuit diagram for the Analog-to-Digital Converter.

MAIN - BEAT BOX CIRCUIT DIAGRAM

Circuit diagram for the Beat Box feature.

FRONT - VFD CIRCUIT DIAGRAM

Circuit diagram for the Vacuum Fluorescent Display.

FRONT - VOLUME CIRCUIT DIAGRAM

Circuit diagram for volume control and LEDs.

FRONT - MIC & PORTABLE CIRCUIT DIAGRAM

Circuit diagram for microphone and portable inputs.

CIRCUIT VOLTAGE CHART

Table of voltage values for key ICs.

SMPS P.C.BOARD (TOP VIEW)

Top view layout of the SMPS printed circuit board.

MAIN P.C.BOARD (TOP VIEW)

Top view layout of the main printed circuit board.

FRONT VFD P.C.BOARD (TOP VIEW)

Top view layout of the VFD printed circuit board.

FRONT_MIC & PORTABLE P.C.BOARD (TOP VIEW)

Top view layout of MIC/Portable PCB.

FRONT VOLUME P.C.BOARD (TOP VIEW)

Top view layout of the volume control PCB.

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