Kenwood KC 206 Service Manual

The Kenwood KC 206 is a professional audio component requiring specialized service and maintenance. This service manual provides comprehensive technical information for qualified service technicians, including schematics, disassembly procedures, alignment instructions, and troubleshooting guidelines. Below are key sections for specifications, block diagrams, circuit descriptions, disassembly procedures, alignment, and troubleshooting.

1. Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Disassembly Procedures 5. Alignment Instructions 6. Parts List 7. Schematic Diagrams 8. PCB Layouts 9. Troubleshooting Guide 10. Safety Precautions

Specifications

Technical specifications for the Kenwood KC 206 audio component.

Parameter	Specification
Power Supply	AC 120V/230V, 50/60Hz
Power Consumption	45W maximum
Frequency Response	20Hz - 20kHz ±1dB
Total Harmonic Distortion	Less than 0.05%
Signal-to-Noise Ratio	Better than 85dB
Input Sensitivity	150mV
Output Level	1V RMS
Dimensions	420mm x 120mm x 300mm
Weight	5.2kg
Operating Temperature	0°C to 40°C

Block Diagrams

System block diagrams showing signal flow and major components.

Main System Block Diagram: Shows overall signal path from input to output stages.
Power Supply Block Diagram: Illustrates AC input, rectification, and regulation circuits.
Audio Processing Block Diagram: Details preamplifier, tone control, and power amplifier sections.
Control System Block Diagram: Shows microprocessor and interface circuits.

WARNING! For qualified technicians only. High voltage present in power supply section.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Power Supply Circuit: Transformer, rectifier diodes, filter capacitors, and voltage regulators.
Preamplifier Stage: Input selector, volume control, and buffer amplifiers.
Tone Control Circuit: Bass and treble control using active filter networks.
Power Amplifier Section: Complementary symmetry output stage with protection circuits.
Protection Circuits: Overcurrent, overvoltage, and thermal protection systems.

CAUTION! Always discharge large capacitors before servicing.

Disassembly Procedures

Step-by-step instructions for disassembling the unit for service access.

Step 1: Remove top cover by unscrewing 6 Phillips screws.
Step 2: Disconnect front panel ribbon cables carefully.
Step 3: Remove front panel assembly by releasing 4 plastic clips.
Step 4: Unscrew main PCB mounting screws (8 locations).
Step 5: Lift PCB assembly while supporting from below.
Step 6: Access power supply and output stages from bottom.

Alignment Instructions

Calibration and alignment procedures for optimal performance.

Adjustment	Procedure	Test Equipment Required
DC Offset	Adjust VR101 for 0V ±10mV at speaker terminals	Digital Multimeter
Bias Current	Set VR102 for 20mA across emitter resistors	Digital Multimeter
Gain Balance	Adjust VR103 for equal output levels	Audio Generator, Oscilloscope
Tone Control Center	Set VR104/105 for flat frequency response	Audio Analyzer

Parts List

Complete list of components with part numbers and specifications.

Transistors: 2SC1815 (Q101-Q110), 2SA1015 (Q201-Q210)
ICs: TA7317P (IC101), NJM4558 (IC201, IC202)
Diodes: 1S1555 (D101-D110), 1N4007 (D201-D204)
Capacitors: Electrolytic: 1000μF/50V (C101), Ceramic: 0.1μF (C201-C210)
Resistors: 1/4W carbon film, various values
Potentiometers: 10kΩ dual gang (VR101), 50kΩ (VR102)

Schematic Diagrams

Complete schematic diagrams for all circuit sections.

Main Amplifier Schematic: Shows complete audio path from input to output.
Power Supply Schematic: Details AC input, rectification, and regulation.
Control Circuit Schematic: Microprocessor and interface circuits.
Protection Circuit Schematic: Overcurrent and thermal protection.

Note: All schematics include component values and test points.

PCB Layouts

Printed circuit board layouts and component placement diagrams.

Main PCB Top Layer: Component side layout with reference designators.
Main PCB Bottom Layer: Solder side showing trace patterns.
Power Supply PCB: Separate board layout for power circuits.
Front Panel PCB: Control and display circuit layout.

Tip: Use these layouts for component location and trace routing.

Troubleshooting Guide

Systematic troubleshooting procedures for common problems.

Symptom	Possible Cause	Corrective Action
No power	Fuse blown, power supply failure	Check F101 (2A), test power supply voltages
No audio output	Amplifier stage failure, protection circuit active	Check output transistors, measure DC offset
Distorted sound	Bias current incorrect, faulty capacitors	Adjust bias current, replace electrolytic capacitors
Intermittent operation	Cold solder joints, cracked traces	Inspect PCB for bad connections, reflow solder
Hum or noise	Ground loop, filter capacitor failure	Check ground connections, replace C101-C104

Safety Precautions

Important safety information for service technicians.

WARNING! High voltages are present in the power supply section. Always disconnect AC power before servicing. Use isolation transformer when testing live circuits. Discharge large capacitors before handling. Use proper grounding techniques to prevent electrostatic discharge damage.

Service Contacts: Kenwood authorized service centers only. For technical support, contact Kenwood service department.