Kenwood TS 520 Service Manual PDF

The Kenwood TS-520 is a classic amateur radio transceiver covering 80-10 meter bands with SSB and CW modes. This service manual provides comprehensive technical documentation including schematics, alignment procedures, troubleshooting guides, parts lists, and maintenance instructions for proper servicing and repair of the TS-520 series transceivers.

1. Technical Specifications 2. Safety Precautions 3. Circuit Description 4. Alignment Procedures 5. Troubleshooting Guide 6. Parts List 7. Block Diagrams 8. Schematic Diagrams 9. Mechanical Assembly 10. Maintenance Schedule 11. Service Notes

Technical Specifications

Complete technical specifications and operating parameters for the Kenwood TS-520 transceiver.

Parameter	Specification
Frequency Coverage	3.5-30 MHz (80-10 meters)
Modes	SSB (USB/LSB), CW
RF Power Output	160W PEP (SSB), 80W (CW)
Receiver Sensitivity	0.5μV for 10dB S+N/N
Selectivity	2.4kHz at -6dB (SSB)
Power Requirements	115/230V AC, 50/60Hz
Tube Complement	6JS6C (Final), 12BY7A (Driver)
Dimensions	380W x 150H x 310D mm
Weight	12.5 kg
Year Introduced	1973

Safety Precautions

Critical safety information for technicians servicing the TS-520 transceiver.

Disconnect AC power before servicing - lethal voltages present.
Discharge high-voltage capacitors before working on power supply.
Use isolation transformer when testing live circuits.
Wear safety glasses when working with high voltage.
Ensure proper grounding of test equipment.

WARNING! High voltages up to 800V DC present in power supply and final amplifier stages. Exercise extreme caution.

Circuit Description

Detailed circuit analysis of major TS-520 subsystems.

Receiver Front End: RF amplifier, mixer, and local oscillator circuits.
IF System: Crystal filter and IF amplifier stages.
Product Detector: SSB detection and BFO circuits.
Transmitter: Microphone amplifier, balanced modulator, and driver stages.
Power Supply: High voltage and low voltage regulation circuits.
VFO System: Variable frequency oscillator and buffer stages.

NOTE: Understanding circuit operation is essential for proper troubleshooting.

Alignment Procedures

Step-by-step alignment instructions for optimal performance.

Receiver Alignment: RF stages, IF amplifiers, and BFO adjustment.
Transmitter Alignment: Carrier suppression, sideband filter, and power amplifier.
VFO Calibration: Band calibration and tracking adjustment.
S-Meter Calibration: Receiver S-meter calibration procedure.
AGC Alignment: Automatic gain control timing and threshold.

Troubleshooting Guide

Systematic troubleshooting approach for common TS-520 problems.

Symptom	Possible Cause	Corrective Action
No receiver audio	BFO failure, audio amp	Check BFO output; test audio stages
Low transmitter power	Final tubes, bias	Replace 6JS6C tubes; check bias voltage
Frequency drift	VFO thermal stability	Check VFO components; replace drift compensation
No transmit/receive	Relay failure	Test T/R relay contacts and coil
Hum in receiver	Power supply ripple	Check filter capacitors; replace if necessary

Parts List

Complete component listing with original Kenwood part numbers.

Tubes: 6JS6C (final), 12BY7A (driver), 6BE6 (mixer)
Transistors: 2SC461 (RF amp), 2SC372 (IF amp)
Crystals: 8.83MHz (IF), various VXO crystals
Transformers: Power, audio output, IF transformers
Capacitors: Electrolytic, ceramic, mica types
Resistors: Carbon composition, metal film

Block Diagrams

System-level block diagrams showing signal flow and interconnections.

Overall System Block Diagram
Receiver Block Diagram
Transmitter Block Diagram
Power Supply Block Diagram
Control Circuit Block Diagram

Tip: Use block diagrams to understand system architecture before detailed circuit analysis.

Schematic Diagrams

Detailed schematic diagrams for all circuit boards and subsystems.

Main Receiver/Transmitter Schematic
Power Supply Schematic
VFO Unit Schematic
Control Unit Schematic
Front Panel Schematic
Final Amplifier Schematic

NOTE: Schematics include component values, test points, and voltage readings.

Mechanical Assembly

Mechanical drawings and assembly instructions.

Chassis Layout: Component placement and mounting
Front Panel: Control layout and assembly
Circuit Boards: PCB layouts and component orientation
Final Assembly: Complete unit assembly sequence
Disassembly Procedure: Step-by-step teardown instructions

Maintenance Schedule

Recommended maintenance intervals and procedures.

Maintenance Item	Interval	Procedure
Tube replacement	2000 hours	Replace final and driver tubes
Contact cleaning	Annual	Clean relay contacts and switches
Alignment check	2 years	Verify receiver and transmitter alignment
Capacitor check	5 years	Test electrolytic capacitors
General cleaning	As needed	Remove dust and debris

Service Notes

Important service bulletins and technical updates.

Service Bulletin TS-520-1: Improved VFO stability modification. Service Bulletin TS-520-2: Final tube bias adjustment procedure. Service Bulletin TS-520-3: Receiver sensitivity improvement. Known Issues: VFO drift in early production units, relay contact oxidation, power supply capacitor failure in humid environments.

Technical Support: For additional service information, contact Kenwood technical support or authorized service centers.