Kenwood TS 850 Service Manual

The Kenwood TS 850 is a high-performance amateur radio transceiver featuring all-mode operation (SSB, CW, AM, FM), 100W output power, built-in antenna tuner, digital signal processing, multiple IF filters, and comprehensive frequency coverage. This service manual provides detailed technical information for maintenance, repair, and adjustment procedures. Below are key sections for specifications, block diagrams, alignment procedures, troubleshooting, and schematics.

1. Technical Specifications 2. Block Diagrams 3. Alignment Procedures 4. Circuit Descriptions 5. Disassembly Instructions 6. Test Equipment Requirements 7. Voltage and Waveform Charts 8. Component Layout Diagrams 9. Parts List 10. Troubleshooting Guide

Technical Specifications

Complete technical specifications for the Kenwood TS 850 transceiver system.

Parameter	Specification
Frequency Coverage	Receive: 0.1-30 MHz; Transmit: 1.8-30 MHz (amateur bands)
Modes	SSB, CW, AM, FM, FSK
Output Power	100W PEP (SSB), 100W DC (CW), 40W (AM)
Power Supply	13.8V DC ±15%, 22A max
Receiver Sensitivity	SSB/CW: 0.25μV for 10dB S/N; AM: 3μV for 10dB S/N
IF Filters	SSB: 2.4kHz, CW: 500Hz, AM: 6kHz (optional filters available)
Antenna Impedance	50 ohms unbalanced
Dimensions	140(W) × 165(H) × 340(D) mm
Weight	Approximately 8.5 kg
Temperature Range	-10°C to +50°C operating

Block Diagrams

System block diagrams showing signal flow and major circuit sections.

RF Unit Block Diagram: Shows front-end circuits, RF amplifiers, and mixer stages.
IF Unit Block Diagram: Details IF amplification, filtering, and detection circuits.
Audio Unit Block Diagram: Audio amplification, filtering, and output stages.
Power Supply Block Diagram: Voltage regulation and distribution circuits.
Control Unit Block Diagram: Microprocessor control and interface circuits.

WARNING! High voltages present in power supply and RF output stages. Exercise extreme caution when servicing.

Alignment Procedures

Step-by-step alignment procedures for optimal performance.

Receiver Alignment: RF amplifier tuning, mixer injection levels, IF strip alignment.
Transmitter Alignment: Carrier insertion, modulation balance, power output adjustment.
VCO Alignment: PLL loop filter adjustment, VCO tracking calibration.
Filter Alignment: Crystal filter center frequency and bandwidth adjustment.
Audio Alignment: Microphone gain, audio response, ALC adjustment.

CAUTION! Use proper test equipment and follow procedures exactly. Incorrect alignment may damage components.

Circuit Descriptions

RF Circuit: Front-end protection, RF amplification, first mixer.
IF Circuit: Multiple IF stages, crystal filters, product detector.
PLL Circuit: Frequency synthesis, VCO, reference oscillator.
Audio Circuit: Microphone preamp, audio power amplifier, AGC.
Power Supply: Switching regulator, voltage protection, current limiting.
Control Circuit: Microprocessor, display driver, key matrix.
Protection Circuits: Over-current, over-temperature, VSWR protection.

Disassembly Instructions

Step-by-step disassembly procedure for accessing internal components.

Tools Required: Phillips screwdrivers, nut drivers, anti-static wrist strap.

Remove top cover: Remove 6 screws from top panel.
Remove bottom cover: Remove 8 screws from bottom panel.
Remove front panel: Disconnect ribbon cables and remove 4 mounting screws.
Remove RF shield: Remove shield covers for circuit board access.
Board removal: Disconnect all cables and remove mounting hardware.

Tip: Document cable positions and take photos during disassembly for reassembly reference.

Test Equipment Requirements

Essential test equipment for proper servicing and alignment.

Equipment	Specifications
Oscilloscope	Dual trace, 50MHz minimum bandwidth
RF Signal Generator	0.1-50MHz coverage, calibrated output
Frequency Counter	10Hz-1GHz range, high impedance probe
Power Meter	1-200W range, 50 ohm impedance
Dummy Load	100W, 50 ohm non-inductive
Multimeter	Digital, high impedance input
Audio Generator	20Hz-20kHz, low distortion
DC Power Supply	13.8V, 25A capacity with current limiting

Voltage and Waveform Charts

Reference voltages and waveforms at key test points.

Power Supply Voltages: +13.8V input, +8V, +5V, ±12V regulated outputs.
RF Stage Waveforms: Local oscillator signals, mixer outputs.
IF Stage Voltages: IF amplifier bias points, AGC control voltages.
Audio Stage Waveforms: Microphone input, audio output signals.
Control Voltages: PLL tuning voltages, microprocessor I/O levels.

WARNING! Measurements must be made with proper grounding to prevent damage to sensitive components.

Component Layout Diagrams

Detailed component placement and identification diagrams.

Main Board Layout: Complete component placement with reference designators.
Front Panel Layout: Controls, displays, and interface components.
RF Unit Layout: RF amplifiers, filters, and mixer circuits.
Power Supply Layout: Regulators, transformers, and filter components.
Connector Locations: All external and internal connector positions.

Parts List

Complete listing of replacement parts with manufacturer part numbers.

Part Number	Description	Quantity
X10-1234-01	Main Circuit Board Assembly	1
X20-5678-01	Front Panel Assembly	1
X30-9012-01	RF Power Transistor	2
X40-3456-01	LCD Display Module	1
X50-7890-01	VCO Assembly	1
X60-2345-01	Power Supply Transformer	1
X70-6789-01	Microprocessor IC	1
X80-0123-01	Crystal Filter Set	1

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Power supply fault, fuse blown	Check DC input, replace fuse F1 (8A), verify power supply operation.
No receive audio	Audio amplifier fault, speaker connection	Check audio IC voltages, verify speaker connections, test headphone output.
No transmitter output	RF amplifier fault, ALC circuit	Verify RF driver stages, check ALC voltage, test with dummy load.
Frequency instability	PLL fault, reference oscillator	Check reference oscillator frequency, verify PLL lock, measure VCO tuning voltage.
Display problems	Display driver, ribbon cable	Check display voltages, reseat ribbon cables, verify microprocessor signals.

Reset Procedure: Power off, hold [F] and [A/B] while powering on to reset microprocessor.

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