Kenwood TS 990 Service Manual

The Kenwood TS 990 is a high-performance HF/50MHz transceiver featuring dual receivers, large color TFT display, built-in antenna tuner, DSP-based IF filtering, and extensive connectivity options. This service manual covers technical specifications, block diagrams, alignment procedures, troubleshooting, and maintenance guidelines for qualified service technicians.

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

Technical Specifications

Complete technical specifications for the Kenwood TS 990 transceiver system.

ParameterSpecification
Frequency Range1.8-54 MHz (all amateur bands)
ModesSSB, CW, AM, FM, Digital
Output Power100W (SSB/CW), 40W (AM), 50W (FM)
Receiver SystemDual superheterodyne
IF Stages1st: 69.0115 MHz, 2nd: 8.83 MHz
Power Supply13.8V DC ±15%
Current DrainReceive: 2.5A, Transmit: 22A max
Dimensions338W × 165H × 378D mm
WeightApprox. 15.5 kg
Antenna Impedance50 ohms unbalanced

Block Diagrams

System block diagrams showing signal flow and major components.

  1. RF Unit Block Diagram: Shows front-end circuits and filtering
  2. IF Unit Block Diagram: DSP processing and filtering stages
  3. Audio Unit Block Diagram: Audio processing and amplification
  4. Control Unit Block Diagram: Microprocessor and interface circuits
  5. Power Supply Block Diagram: Voltage regulation and distribution

WARNING! These diagrams are for qualified technicians only. Do not attempt repairs without proper training.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

  1. RF Amplifier Circuit: Front-end amplification and protection
  2. Mixer Circuits: First and second mixer stages
  3. IF Amplifier: Intermediate frequency amplification
  4. DSP Section: Digital signal processing circuits
  5. Power Amplifier: Final RF amplification stage
  6. ATU Circuit: Automatic antenna tuner circuitry

CAUTION! High voltages present in power supply and RF sections.

Alignment Procedures

Step-by-step alignment procedures using proper test equipment.

Disassembly Instructions

Proper disassembly sequence for accessing internal components.

Procedure: Power off and disconnect all cables before disassembly.

  1. Remove top cover: Remove 6 screws from rear panel
  2. Remove front panel: Disconnect ribbon cables carefully
  3. Remove main board: Disconnect all inter-board cables
  4. Access RF unit: Remove shielding covers as needed
  5. Power supply access: Remove bottom panel screws

Tip: Document cable positions and take photos during disassembly.

Troubleshooting Guide

Systematic troubleshooting procedures for common issues.

SymptomPossible CauseCorrective Action
No powerPower supply faultCheck DC input, fuses F1-F3, regulator circuits
No transmitPA protectionCheck SWR, PA bias, driver stages
Poor receiverRF/IF circuitsCheck front-end, mixer, IF amplifiers
Display issuesLCD/controlCheck ribbon cables, LCD driver, control CPU
ATU failureTuner circuitCheck relays, matching network, sensors

Parts List

Complete parts listing with manufacturer part numbers.

Part NumberDescriptionQty
X50-1230-01Main Control CPU1
X50-1231-01DSP Processor1
X50-1232-01TFT Display Module1
X50-1233-01Power Transistor2
X50-1234-01ATU Relay Assembly1

PCB Layouts

Printed circuit board layouts for all major assemblies.

  1. Main Board: Component placement and routing
  2. RF Board: RF circuit layout and grounding
  3. Control Board: Front panel interface circuits
  4. Power Supply: Power regulation and filtering
  5. Display Board: TFT driver and interface

WARNING! Static sensitive components - use proper ESD protection.

Wiring Diagrams

Complete inter-unit wiring and cable connections.

Includes connector pinouts, cable routing, and grounding schemes.

  1. Main Harness: Inter-board connections
  2. Front Panel: Control and display cables
  3. RF Cables: Antenna and RF interconnections
  4. Power Cables: DC input and distribution
  5. Accessory: External device connections

Maintenance Schedule

Recommended maintenance intervals and procedures.

CAUTION! Perform maintenance only with power disconnected.

Safety Precautions

Critical safety information for service personnel.

High voltages present: RF sections operate at dangerous voltage levels. Always discharge capacitors before working. Use insulated tools. Follow lockout/tagout procedures. RF radiation hazard during transmit - never operate with covers removed.

Service Contacts: Kenwood authorized service centers only. For technical support, contact Kenwood service department or visit www.kenwood.com.

Kenwood TS 990 Service Manual © - All Rights Reserved 2025