Kenwood TS-120S Service Manual PDF

The Kenwood TS-120S is a high-performance amateur radio transceiver covering the HF bands with SSB, CW, and AM modes. This service manual provides comprehensive technical information including schematics, alignment procedures, troubleshooting guides, parts lists, and maintenance instructions for qualified service technicians. Below are key sections covering specifications, block diagrams, circuit descriptions, alignment procedures, and repair guidelines.

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

Technical Specifications

Complete technical specifications for the Kenwood TS-120S transceiver including frequency coverage, modes, power requirements, and performance characteristics.

Parameter	Specification
Frequency Coverage	1.8-30 MHz (amateur bands)
Modes	SSB, CW, AM
RF Power Output	100W PEP (SSB), 100W (CW), 40W (AM)
Receiver Sensitivity	0.25μV for 10dB S+N/N
Selectivity	2.4kHz (-6dB), 4.5kHz (-60dB)
Power Requirements	13.8V DC ±15%, 20A max
Dimensions	280(W) × 95(H) × 260(D) mm
Weight	5.2 kg
Impedance	50 ohms unbalanced
Temperature Range	-10°C to +50°C

Block Diagrams

Detailed block diagrams showing signal flow through the transmitter and receiver sections.

Receiver Block Diagram: RF input to audio output signal path
Transmitter Block Diagram: Microphone input to RF output stages
PLL Synthesizer Block Diagram: Frequency generation system
Power Supply Block Diagram: DC power distribution

WARNING! High voltages present in power supply and transmitter sections. Exercise extreme caution when servicing.

Circuit Descriptions

Detailed circuit analysis of major sections including component functions and signal processing.

Receiver Front End: RF amplifier and mixer circuits
IF System: Crystal filters and IF amplification
Product Detector: SSB/CW demodulation circuits
Transmitter Driver: Exciter and driver stages
Power Amplifier: Final RF power amplification
PLL Circuit: Frequency synthesizer operation

CAUTION! Static-sensitive components present. Use proper ESD protection during service.

Alignment Procedures

Receiver Alignment: RF stages, IF amplifiers, BFO adjustment
Transmitter Alignment: Driver stages, power amplifier, ALC circuits
PLL Alignment: VCO adjustment, reference oscillator calibration
Filter Alignment: Crystal filter adjustment and testing
Meter Calibration: S-meter and power meter calibration
Required Equipment: Signal generator, oscilloscope, power meter, frequency counter
Test Points: Designated test points on main PCB
Alignment Software: Special software tools for digital alignment

Troubleshooting Guide

Systematic troubleshooting procedures for common problems and performance issues.

Symptom-Based Diagnosis: No receive, no transmit, poor sensitivity, frequency drift, meter malfunctions.

Receiver: Check RF stages, IF amplifiers, BFO, audio circuits. Transmitter: Verify driver stages, PA, modulation circuits. Power Supply: Test voltage regulators, current limits. Control System: Microprocessor, display, encoder functions.

Parts List

Complete component listing with part numbers, descriptions, and specifications.

Semiconductors: Transistors, diodes, ICs with replacement cross-references
Passive Components: Resistors, capacitors, inductors with values and tolerances
Mechanical Parts: Knobs, connectors, hardware with specifications
Test Equipment: Required service instruments and calibration tools

Tip: Use genuine Kenwood parts for optimal performance and reliability.

PCB Layouts

Detailed printed circuit board layouts showing component placement and trace routing.

Main Board: Component side and solder side views
Front Panel Board: Control and display circuits
Power Supply Board: Regulator and filter circuits
RF Board: Transmitter and receiver RF sections
Grounding Scheme: Proper grounding techniques and points
Shielding: RF shielding locations and requirements

WARNING! High current traces identified. Ensure proper clearance during repairs.

Mechanical Assembly

Exploded views and assembly instructions for mechanical components.

Maintenance Schedule

Recommended maintenance intervals and procedures for optimal performance.

CAUTION! Disconnect power before performing any maintenance. Allow capacitors to discharge completely.

Safety Precautions

Important safety information for service personnel including high voltage warnings, ESD protection, and proper test equipment usage.

Service Notes

Problem	Common Causes	Recommended Action
No power	Fuse, power supply	Check main fuse; test power supply voltages; verify DC input.
No transmit	Driver stages, relays	Verify driver operation; check TR switching relays; test PA bias.
Poor receiver sensitivity	RF stages, filters	Test RF amplifier; check crystal filters; verify AGC operation.
Frequency drift	PLL, reference oscillator	Check PLL lock; test reference oscillator stability; verify VCO.
Display problems	Microprocessor, connections	Verify µP operation; check display connections; test voltages.

Factory Service: Authorized Kenwood service centers for complex repairs.

Technical Support: Contact Kenwood technical support for service bulletins and updates.