Kenwood TK 780 Service Manual

The Kenwood TK 780 is a VHF/UHF mobile radio designed for professional and commercial use, featuring robust construction, wide frequency coverage, multiple channel capacity, and advanced communication capabilities. This service manual covers technical specifications, installation procedures, programming instructions, maintenance guidelines, and troubleshooting for authorized service personnel.

1. Technical Specifications 2. Installation Procedures 3. Programming Instructions 4. Circuit Description 5. Alignment Procedures 6. Disassembly/Reassembly 7. Maintenance Schedule 8. Parts List 9. Block Diagrams 10. Troubleshooting Guide

Technical Specifications

The Kenwood TK 780 offers comprehensive radio communication capabilities with advanced features for professional applications.

Specification	Details
Frequency Range	VHF: 136-174 MHz / UHF: 400-470 MHz
Channel Capacity	Up to 256 channels
Output Power	VHF: 45W / UHF: 40W (programmable)
Power Supply	13.8V DC ±15%
Current Consumption	Receive: 0.5A / Transmit: 11A (max)
Modulation	16KΦF3E (FM)
Dimensions	140(W) × 40(H) × 170(D) mm
Weight	Approx. 1.1 kg
Operating Temperature	-30°C to +60°C
Frequency Stability	±2.5 ppm

Installation Procedures

Proper installation ensures optimal performance and longevity of the radio equipment.

Mounting: Secure radio unit using mounting bracket in vehicle
Power Connection: Connect red wire to positive terminal, black wire to negative terminal
Antenna Installation: Install compatible antenna with proper grounding
Microphone Connection: Connect microphone to front panel connector
External Speaker: Connect optional external speaker if required

WARNING! Ensure proper fuse protection and secure all connections to prevent electrical hazards.

Programming Instructions

Programming requires KPG-49D programming software and programming cable.

Connect programming cable to radio and computer
Launch KPG-49D software and read current configuration
Set frequency, CTCSS/DCS codes, and channel parameters
Configure scan lists and priority channels
Write configuration to radio and verify operation

CAUTION! Only qualified personnel should perform programming operations.

Circuit Description

RF Unit: Contains transmitter and receiver circuits with filtering
PLL Synthesizer: Provides stable frequency generation
Audio Processing: Includes microphone preamp and audio power amplifier
Control Unit: Microprocessor-based control system
Power Supply: Regulated DC-DC converter circuits
Modulator/Demodulator: FM modulation and demodulation circuits

Alignment Procedures

Alignment requires proper test equipment and should be performed by qualified technicians.

Required Equipment: Spectrum analyzer, frequency counter, RF power meter, audio generator, DC power supply, dummy load.

Transmitter Alignment: Adjust carrier frequency, modulation balance, and power output. Receiver Alignment: Set receiver sensitivity, squelch threshold, and audio output levels.

Disassembly/Reassembly

Follow proper procedures to avoid damage during service operations.

Remove front panel screws and carefully separate front assembly
Detach control head from main unit if required
Remove circuit boards for component-level service
Handle flex cables and connectors with care
Reassemble in reverse order, ensuring all connections are secure

Tip: Document screw locations and use proper anti-static precautions.

Maintenance Schedule

Regular maintenance ensures reliable operation and extends equipment life.

Interval	Maintenance Task
Monthly	Visual inspection, connection check, cleaning
6 Months	Performance check, antenna inspection
Annual	Complete alignment, component testing
As Needed	Software updates, battery replacement

Parts List

Genuine Kenwood parts ensure compatibility and performance.

Main Components: Main circuit board, control head, microphone, mounting bracket, DC cable, fuse holder.

Replacement Parts: Power transistors, RF modules, display, buttons, connectors, capacitors.

Ordering Information: Contact authorized Kenwood parts distributor with model number and part code.

Block Diagrams

System block diagrams illustrate signal flow and circuit relationships.

Transmitter Block: Microphone → Audio Processor → Modulator → RF Amplifier → Antenna

Receiver Block: Antenna → RF Amplifier → Mixer → IF Amplifier → Demodulator → Audio Amplifier → Speaker

Control System: CPU → Display Driver → Key Matrix → Memory → Interface Circuits

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Power cable, fuse, internal supply	Check fuse (15A), verify power connections, test internal power supply
No transmission	PTT switch, microphone, RF circuit	Test PTT circuit, check microphone, verify RF power output
No reception	Speaker, audio circuit, squelch	Test speaker, check audio amplifier, adjust squelch setting
Poor audio quality	Microphone, audio processing	Replace microphone, check audio processing circuits
Frequency error	PLL circuit, reference oscillator	Adjust reference oscillator, check PLL lock condition

Reset Procedure: Hold [MONI] + [LAMP] while powering on to reset to factory defaults.

Service Support: Contact authorized Kenwood service center for technical assistance.