LG AK815 Service Manual

The LG AK815 is a high-performance audio system featuring CD playback, AM/FM radio tuner, cassette deck, and auxiliary input capabilities. This service manual provides comprehensive technical information for service technicians, including disassembly procedures, circuit diagrams, troubleshooting guides, and replacement part specifications. Below are key sections for technical specifications, maintenance procedures, troubleshooting, and parts information.

1. Product Overview 2. Technical Specifications 3. Disassembly Procedures 4. Circuit Diagrams 5. Troubleshooting Guide 6. Parts List 7. Alignment Procedures 8. Service Precautions 9. Test Points 10. Firmware Information 11. Contact Information

Product Overview

The LG AK815 audio system consists of main unit with CD player, cassette deck, tuner section, and control panel. Key components: Main PCB, power supply board, display module, mechanism assembly, and front panel controls.

Component	Description
Main PCB	Central processing unit with audio processing circuits
Power Supply Board	AC/DC conversion and voltage regulation
Display Module	LED/LCD display with driver circuitry
CD Mechanism	Laser pickup and loading mechanism assembly
Cassette Deck	Playback/recording mechanism with head assembly
Tuner Module	AM/FM radio reception circuitry
Front Panel	Control buttons and input/output connectors
Speaker Terminals	Left/right channel output connections
Power Transformer	Main power conversion component
Heat Sink	Amplifier stage cooling

Technical Specifications

Power Requirements: AC 120V, 60Hz
Power Consumption: 45W maximum
Output Power: 20W RMS per channel (8 ohm)
Frequency Response: 20Hz - 20kHz (±3dB)
Signal-to-Noise Ratio: >75dB (CD playback)
Tuner Section: AM/FM stereo with 30 station presets
CD Compatibility: CD, CD-R, CD-RW
Cassette Section: Normal position playback/recording
Dimensions: 430mm(W) x 125mm(H) x 320mm(D)
Weight: 5.2kg

Disassembly Procedures

Follow these steps for safe disassembly of the unit.

Power off and unplug the unit from AC outlet.
Remove all screws from rear panel and side panels.
Carefully separate top cover from main chassis.
Disconnect all ribbon cables and wiring harnesses.
Remove front panel assembly by releasing plastic clips.
Extract main PCB by removing mounting screws.
Access CD mechanism by removing mechanism shield.

WARNING! Always discharge capacitors before working on power supply section. Use proper ESD protection.

Circuit Diagrams

Complete schematic diagrams for all circuit sections.

Main System Block Diagram: Shows signal flow between major components
Power Supply Circuit: +12V, +5V, and -12V regulation circuits
Audio Amplifier Section: Stereo amplifier with tone control
CD Servo Circuits: Focus, tracking, and spindle motor control
Tuner Section: AM/FM demodulation and IF amplification
Display Driver: Segment and grid driving circuitry
Control System: Microprocessor and interface circuits

Note: All voltages measured with respect to chassis ground.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check F101 (2A); verify AC input; test power switch
No CD operation	Laser pickup, spindle motor	Clean lens; check laser diode; test motor voltage
No sound output	Amplifier IC, speakers	Test IC201 (STA777); check speaker connections
Display not working	Display driver, ribbon cable	Check CN301 connection; test display voltages
Cassette not playing	Belt, motor, head	Replace drive belt; clean head; test motor operation
No radio reception	Tuner module, antenna	Check antenna connection; test tuner IC voltages

Parts List

Replacement parts with manufacturer part numbers.

Part Number	Description	Qty
AK815-001	Main PCB Assembly	1
AK815-002	CD Mechanism Assembly	1
AK815-003	Laser Pickup Unit	1
AK815-004	Power Transformer	1
AK815-005	Display Module	1
AK815-006	Cassette Mechanism	1
AK815-007	Front Panel Assembly	1
AK815-008	Main IC (STA777)	1
AK815-009	Tuner Module	1
AK815-010	Drive Belt Kit	1

Alignment Procedures

Technical adjustment procedures for optimal performance.

Laser Power Adjustment: Adjust VR101 for optimal RF signal
Focus Gain: Set VR102 for proper focus servo
Tracking Balance: Adjust VR103 using test disc
FM Tuner Alignment: Set FM oscillator and RF stages
Cassette Head Azimuth: Adjust for maximum high frequency
Output Level Calibration: Set audio output levels

CAUTION! Use proper test equipment and follow safety procedures.

Service Precautions

Important safety information for service technicians.

Always disconnect AC power before servicing
Use isolation transformer when testing live circuits
Observe ESD precautions when handling ICs
Replace components with exact specifications
Keep work area clean and organized
Use proper tools and test equipment
Document all modifications and repairs

WARNING! High voltages present in power supply section.

Test Points

Key test points for voltage and signal measurements.

Test Point	Description	Normal Value
TP1	+12V Supply	+12V DC ±5%
TP2	+5V Digital	+5V DC ±3%
TP3	-12V Supply	-12V DC ±5%
TP4	RF Signal	1.2Vp-p (CD playing)
TP5	Focus Error	0V ±0.5V (tracking)
TP6	Tracking Error	0V ±0.5V (tracking)
TP7	Audio Output	Variable (signal dependent)

Firmware Information

Software and firmware specifications.

Main Microprocessor: 8-bit microcontroller
Firmware Version: V2.1 (latest)
Update Method: ROM replacement only
Default Settings: Factory reset procedure available
Error Codes: Display shows error codes for diagnostics

Contact Information

For technical support and parts ordering:

LG Service Center: 1-800-243-0000
Technical Support: [email protected]
Parts Department: [email protected]
Website: www.lgservice.com
Service Hours: Mon-Fri 8:00 AM - 8:00 PM EST

Note: Have model number and serial number ready when contacting support.