Nakamichi 420 Service Manual

Provided to Naks.com by Willy Hermann Services willyhs.com

Nakamichi 420 Specifications

General

Frequency Response	20Hz to 20kHz
Speaker Load Impedance	4Ω to 16Ω
Total Harmonic Distortion	0.1%
Input Impedance	50kΩ
Input Sensitivity	150mV
Power Output	20 watts per channel into 8Ω (stereo)

Summary

1. General

Cautions

Important safety precautions regarding capacitor discharge and handling.

2. Principle of Operation

2.3. Power Block Output Stage

Details on the output stage design, transistor configuration, and distortion characteristics.

3. Removal Procedures

4. Readjustment of Power Block

4.5. Semiconductor Balance and Distortion Check

Procedure for balancing semiconductors and checking distortion requirements.

7. Wiring Diagram

8. Performance Data

9. Block Diagram

10. Schematic Diagram

12. Specifications

Service Bulletin: Addition of Protector Circuit

Purpose of Protector Circuit

Explains the addition of a circuit to prevent speaker damage from amplifier malfunctions.

Modification Details

Describes changes to the power block and rear panel assemblies for the protector circuit.

Modified and Additional Parts

Principle of Protector Circuit Operation

Details how the protector circuit operates to safeguard speakers from DC voltage.