Kenwood Basic C2 Service Manual

The Kenwood Basic C2 is a high-quality stereo preamplifier featuring multiple input sources, tone controls, phono stage, tape monitoring, and advanced audio circuitry. Designed for audiophiles and professional use, it delivers exceptional sound quality with low distortion and wide frequency response. Below are key sections for technical specifications, circuit diagrams, service procedures, adjustments, and troubleshooting.

1. Technical Specifications 2. Block Diagram 3. Circuit Description 4. Disassembly Instructions 5. Service Adjustments 6. Parts List 7. PCB Layouts 8. Wiring Diagrams 9. Troubleshooting Guide 10. Safety Precautions

Technical Specifications

Key performance characteristics and electrical parameters of the Kenwood Basic C2 preamplifier.

ParameterSpecification
Frequency Response5Hz - 100kHz (+0, -3dB)
Total Harmonic Distortion0.005% (1kHz)
Input SensitivityPhono: 2.5mV, Line: 150mV
Signal-to-Noise RatioPhono: 85dB, Line: 100dB
Tone Control RangeBass: ±10dB, Treble: ±10dB
Input ImpedancePhono: 47kΩ, Line: 50kΩ
Output Voltage1V (rated), 8V (max)
Power RequirementsAC 120V, 60Hz, 15W
Dimensions440 x 85 x 300mm (WxHxD)
Weight4.5kg

Block Diagram

System overview showing signal flow and major functional blocks.

  1. Input Selector: Phono, CD, Tuner, Aux, Tape 1, Tape 2
  2. Phono Equalizer: RIAA correction network
  3. Tone Control: Bass and treble adjustment circuits
  4. Volume Control: Precision stepped attenuator
  5. Output Buffer: Low impedance driver stage
  6. Power Supply: Regulated ±15V DC rails

NOTE! All signal paths are fully discrete for optimal audio performance.

Circuit Description

Detailed explanation of major circuit sections and their operation.

  1. Phono Stage: Dual JFET input with RIAA equalization
  2. Line Stage: High-speed op-amp based amplification
  3. Tone Control: Baxandall-type active tone circuit
  4. Power Supply: Dual secondary transformer with regulation
  5. Protection Circuit: DC offset and overload protection

CAUTION! High voltages present - discharge capacitors before servicing.

Disassembly Instructions

Service Adjustments

Critical calibration procedures for optimal performance.

DC Offset: Adjust VR101/VR102 for 0mV ±5mV at output

Phono Gain: Verify 40dB gain at 1kHz with 2.5mV input

Tone Control: Center position should yield flat response

Power Supply: Check ±15V DC rails within 5% tolerance

Parts List

Key components with manufacturer part numbers.

ComponentPart NumberDescription
Power TransformerT-1001Dual 18V secondary
Main CapacitorsC101-C1044700μF/35V electrolytic
Input JFETsQ101-Q1022SK170 matched pair
Op-ampsIC101-IC103NJM4558
Volume PotVR001100kΩ audio taper

PCB Layouts

Component placement and trace routing diagrams.

  1. Main Audio Board: Top and bottom layer views
  2. Power Supply Board: Component orientation
  3. Front Panel Board: Switch and LED locations
  4. Grounding Scheme: Star ground implementation

Tip: Use exact replacement components for critical audio paths.

Wiring Diagrams

Interconnection schematics between assemblies.

  1. Power Supply to Main Board: ±15V, GND connections
  2. Front Panel to Main Board: Control signal wiring
  3. Input/Output Jacks: Shielded cable routing
  4. Ground Loops: Proper chassis grounding

WARNING! Observe polarity on electrolytic capacitors.

Troubleshooting Guide

SymptomPossible CauseCorrective Action
No outputPower supply failureCheck fuse F101, measure DC rails
Distorted soundDC offset incorrectAdjust VR101/VR102 for 0mV
Hum/buzzGrounding issueVerify chassis ground, shield connections
Intermittent operationCold solder jointsResolder main power connectors
Phono not workingJFET failureReplace Q101-Q102 matched pair

Safety Precautions

Always disconnect AC power before servicing. Use insulated tools. Discharge large capacitors. Work on anti-static mat. Follow local electrical safety codes.

CAUTION! Line voltage present - risk of electric shock.

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