Kenwood NX-800 Service Manual

The Kenwood NX-800 is a professional digital/analog mobile radio designed for commercial and public safety applications. This service manual covers technical specifications, disassembly procedures, alignment instructions, troubleshooting, and maintenance guidelines for the NX-800 series radios. Below are key sections for technical overview, disassembly, alignment, testing, and repair procedures.

1. Technical Specifications 2. Disassembly Procedures 3. Alignment and Adjustment 4. Circuit Descriptions 5. Troubleshooting Guide 6. Parts List and Diagrams 7. Test Equipment Requirements 8. Firmware Programming 9. Maintenance Schedule 10. Safety Precautions 11. Contact Information

Technical Specifications

Key technical parameters and operating characteristics of the Kenwood NX-800 mobile radio.

Parameter	Specification
Frequency Range	136-174 MHz / 400-520 MHz
Output Power	45W (VHF) / 40W (UHF)
Modulation	16K0F3E (Analog) / 8K30F1E (NXDN Digital)
Channel Capacity	512 Channels
Power Supply	13.8V DC ±15%
Current Consumption	Receive: 0.8A / Transmit: 11A (max)
Operating Temperature	-30°C to +60°C
Dimensions	160(W) x 50(H) x 165(D) mm
Weight	Approx. 1.2 kg
IP Rating	IP54/55

Disassembly Procedures

Step-by-step instructions for disassembling the NX-800 radio for service and repair.

Remove mounting bracket: Loosen four screws on bottom of radio.
Remove top cover: Remove six screws and carefully lift cover.
Remove front panel: Disconnect flex cable and remove four screws.
Remove main board: Disconnect all cables and remove eight mounting screws.
Remove RF unit: Separate RF shield and disconnect RF connectors.

WARNING! Always disconnect power before disassembly. Use proper anti-static precautions.

Alignment and Adjustment

Required test equipment and procedures for aligning transmitter and receiver circuits.

Transmitter Power Adjustment: Adjust VR201 for high power, VR202 for low power.
Frequency Deviation: Adjust VR101 for proper modulation level.
Receiver Sensitivity: Adjust L101/L102 for optimal squelch sensitivity.
PLL Alignment: Verify lock range and adjust VC101 if necessary.
Audio Output: Adjust VR301 for proper audio level.

CAUTION! Use calibrated test equipment. Follow all RF safety procedures.

Circuit Descriptions

RF Unit: Contains PA module, receive preamp, and antenna switching.
Main Board: Digital signal processing, control logic, and power regulation.
Power Supply: Switching regulator provides 5V, 8V, and 3.3V rails.
Audio Circuit: Includes microphone preamp, audio power amp, and sidetone generation.
Control Head: Display, buttons, and interface to main unit.
Synthesizer: PLL circuit with TCXO reference for frequency stability.

Troubleshooting Guide

Common symptoms and diagnostic procedures for NX-800 radio issues.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power cable, regulator	Check F101 fuse; verify 13.8V at power connector; test Q101 regulator.
No transmit	PA module, PLL, mic circuit	Check PA bias voltage; verify PLL lock; test mic input circuit.
No receive	RF amp, mixer, IF filter	Test RF amplifier stages; check mixer output; verify IF filter integrity.
Poor audio	Speaker, audio IC, volume control	Test speaker continuity; check IC301 audio amplifier; verify volume pot.
Display issues	LCD, flex cable, controller	Check LCD contrast; reseat flex cable; test display controller IC.

Parts List and Diagrams

Reference materials for component identification and replacement parts.

Main PCB Assembly: Part number KES-5XXXXX
RF Unit Assembly: Part number KES-5XXXXX
Front Panel Assembly: Part number KES-5XXXXX
Power Supply Module: Part number KES-5XXXXX
Case and Hardware: Part number KES-5XXXXX

Note: Always use genuine Kenwood replacement parts for optimal performance.

Test Equipment Requirements

Essential test equipment for proper service and alignment of NX-800 radios.

DC Power Supply: 13.8V DC, 15A capacity with current limiting
RF Power Meter: 1-100W range, 50 ohm impedance
Frequency Counter: 1 GHz minimum with high impedance probe
Oscilloscope: 50 MHz dual trace with probe set
Audio Generator: 300Hz-3kHz sine wave output
DMM: Digital multimeter with voltage/current/resistance measurement
Service Software: KPG-111D programming software

Firmware Programming

Procedures for updating firmware and programming radio features.

Connect programming cable to radio and PC.
Launch KPG-111D programming software.
Read current configuration from radio.
Make required changes to frequencies, tones, and features.
Write new configuration to radio memory.
Verify operation and perform alignment if necessary.

WARNING! Always backup current configuration before making changes.

Maintenance Schedule

Recommended maintenance intervals and procedures for optimal performance.

Interval	Maintenance Task
Monthly	Visual inspection, connector check, cleaning
6 Months	Performance verification, battery check
Annual	Full alignment, firmware update, preventive maintenance
As Needed	Repair, parts replacement, major service

Safety Precautions

Important safety information for service technicians.

ELECTRICAL SAFETY: Disconnect power before servicing. Use isolation transformer when working on live circuits.

RF SAFETY: Never operate transmitter without proper antenna or dummy load. Maintain safe distance from antenna during transmission.

ESD PROTECTION: Use grounded wrist strap and anti-static mat when handling circuit boards.

Contact Information

Kenwood service support and technical assistance resources.

Kenwood USA Corporation Technical Support: 1-800-950-5005

Service Center Locator: www.kenwood.com/usa

Technical Documentation: www.kenwood.com/electronics

Service Hours: Monday-Friday, 8:00 AM - 5:00 PM PST