Kenwood TR 7950 Service Manual

The Kenwood TR 7950 is a professional-grade amateur radio transceiver featuring 2-meter VHF operation with 50W output power, 200 memory channels, CTCSS/DCS encode/decode, wide frequency coverage from 136-174MHz, dual receive capability, robust construction for mobile use, and comprehensive programming options. Below are key sections for technical specifications, installation, operation, maintenance, and troubleshooting.

1. Technical Specifications 2. Installation Guide 3. Front Panel Controls 4. Basic Operation 5. Advanced Features 6. Programming Instructions 7. Maintenance Procedures 8. Alignment Procedures 9. Circuit Diagrams 10. Parts List 11. Troubleshooting Guide

Technical Specifications

Complete technical specifications for the Kenwood TR 7950 transceiver.

Parameter	Specification
Frequency Range	136-174 MHz (Rx/Tx)
Output Power	50W (High), 25W (Mid), 5W (Low)
Memory Channels	200 channels
Voltage Requirement	13.8V DC ±15%
Current Consumption	12A (Tx max), 0.8A (Rx max)
Modulation	16KΦF3E (FM)
Antenna Impedance	50 ohms
Dimensions	140(W) × 45(H) × 180(D) mm
Weight	1.2 kg
Temperature Range	-20°C to +60°C

Installation Guide

Proper installation procedures for mobile or base station operation.

Mounting: Secure transceiver using mounting bracket in vehicle or desktop.
Power Connection: Connect red wire to positive terminal, black wire to negative terminal with appropriate fuse.
Antenna Installation: Install 50-ohm antenna with proper grounding.
Microphone Connection: Plug microphone into front panel MIC jack.
External Speaker: Connect optional external speaker if required.

WARNING! Ensure proper fuse rating (15A recommended). Verify polarity before connecting power to prevent damage.

Front Panel Controls

Description of all front panel controls and indicators.

Main Controls: POWER switch, VOLUME control, SQL control, Channel selector knob, Function (F) button.

Display Indicators: LCD shows frequency, channel number, mode indicators (TX, BUSY, LOCK), power level, CTCSS/DCS status.

Buttons: MHz/SCAN, A/B (band select), LAMP, TONE, REV, CALL, DUAL, LOCK, V/M, F/W buttons for menu access.

Basic Operation

Fundamental operating procedures for the TR 7950.

Power On: Turn POWER switch clockwise to activate unit.
Volume/Squelch: Adjust VOLUME for audio level, SQL to eliminate background noise.
Frequency Selection: Use channel selector or direct frequency entry.
Transmit: Press and hold PTT on microphone to transmit.
Channel Memory: Store frequently used frequencies in memory channels.

CAUTION! Ensure proper antenna connection before transmitting to prevent RF damage.

Advanced Features

Dual Watch: Monitor two frequencies simultaneously.
CTCSS/DCS: Encode/decode for private communications.
Scan Functions: Programmable scan with priority channel.
Time-out Timer: Automatic transmit time limit.
Busy Channel Lockout: Prevents transmission on busy channels.
1750 Hz Tone Burst: For repeater access in European systems.

Programming Instructions

Step-by-step programming guide for memory channels and functions.

Enter Program Mode: Press F then V/M button.
Select Memory Channel: Use channel selector or numeric entry.
Set Frequency: Enter desired frequency using keypad.
Configure Options: Set offset, tone, power level as required.
Save: Press F then V/M again to store settings.

Tip: Use PC programming cable and software for bulk programming.

Maintenance Procedures

Routine maintenance and cleaning procedures.

Exterior Cleaning: Use soft, dry cloth for front panel and case.
Connector Inspection: Regularly check antenna and power connectors.
Fan Cleaning: Clean cooling fan intake periodically.
Firmware Updates: Check for latest firmware versions.

WARNING! Disconnect power before performing any maintenance. Do not use chemical cleaners.

Alignment Procedures

Technical alignment procedures for qualified service personnel only.

Alignment	Procedure	Test Equipment
Receiver Sensitivity	Adjust L101, L102 for maximum sensitivity	Signal generator, voltmeter
Transmitter Power	Adjust L301 for 50W output	Power meter, dummy load
Frequency Calibration	Adjust TC101 for precise frequency	Frequency counter
Modulation Deviation	Set R311 for 5kHz deviation	Modulation meter

Circuit Diagrams

Reference circuit diagrams for troubleshooting and repair.

Main Receiver Circuit
Transmitter Power Amplifier
Frequency Synthesizer
Control Unit Microprocessor
Power Supply Regulation
Audio Processing Circuit

Note: Complete schematic diagrams available in full service manual.

Parts List

Critical replacement parts and components.

Part Number	Description	Notes
X51-1350-10	Main PCB Assembly	Complete board
X52-1450-11	Front Panel Assembly	Includes display
X53-1550-12	RF Power Module	50W output
X54-1650-13	Cooling Fan Assembly	With motor
X55-1750-14	Microphone Assembly	With cable

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Power connection, fuse	Check power cable, replace 15A fuse
No transmit	PTT switch, settings	Check microphone, verify channel settings
Poor reception	Antenna, squelch	Verify antenna connection, adjust squelch
Display issues	Contrast, backlight	Adjust contrast control, check backlight
Overheating	Fan, ventilation	Clean fan, ensure adequate airflow

Reset Procedure: Turn off unit, hold LAMP and TONE buttons while turning on.

Service Contact: Authorized Kenwood service centers only.