Kenwood TM-271A Service Manual

The Kenwood TM-271A is a 2-meter amateur radio transceiver featuring 65W output power, wide frequency coverage (136-174MHz), 207 memory channels, CTCSS/DTCS encode/decode, built-in DTMF microphone, weather alert function, and rugged construction for mobile operation. Below are key sections for technical specifications, service procedures, alignment, troubleshooting, and maintenance.

1. Technical Specifications 2. Service Precautions 3. Disassembly Procedures 4. Circuit Description 5. Alignment Procedures 6. Voltage Measurements 7. Troubleshooting Guide 8. Parts List 9. Schematic Diagrams 10. Mechanical Information 11. Service Notes

Technical Specifications

Key technical parameters and operating characteristics of the TM-271A transceiver.

Parameter	Specification
Frequency Range	136-174 MHz (Rx/Tx)
Output Power	65W (High), 25W (Mid), 5W (Low)
Power Supply	13.8V DC ±15%
Current Consumption	15A max (Tx), 1.5A (Rx max audio)
Modulation System	16F3 (FM)
Channel Spacing	12.5/20/25 kHz
Memory Channels	207 (200 regular + 6 scan edges + 1 call)
Antenna Impedance	50 ohms
Operating Temperature	-20°C to +60°C
Dimensions	140(W) × 40(H) × 170(D) mm

Service Precautions

Important safety information and precautions for service technicians.

Disconnect power before servicing or replacing components.
Use proper ESD protection when handling circuit boards.
Ensure correct polarity when connecting power supply.
Use only specified replacement parts.

WARNING! High voltages present in RF power amplifier section. Use appropriate safety equipment and procedures.

Disassembly Procedures

Step-by-step instructions for disassembling the transceiver.

Remove six screws from bottom case.
Carefully separate top and bottom cases.
Disconnect front panel ribbon cable from main board.
Remove main board mounting screws.
Lift main board for access to internal components.

CAUTION! Handle ribbon cables carefully to avoid damage to connectors.

Circuit Description

Detailed description of major circuit blocks and their functions.

RF Amplifier: 2SC3357 transistor for initial RF amplification.
Mixer Stage: Double-balanced mixer using diodes for frequency conversion.
IF Section: 10.7MHz ceramic filters and IC for intermediate frequency processing.
PLL Circuit: MB15E03SL PLL IC with 12.8MHz reference oscillator.
Power Amplifier: 2SC3102 final transistor with heat sink.
Audio Section: TA7368F audio power amplifier IC.
Control Circuit: Microprocessor-based control system.

Alignment Procedures

Required test equipment and step-by-step alignment procedures.

Test Equipment Required: Frequency counter, RF power meter, modulation meter, DC power supply, dummy load, signal generator, oscilloscope.

PLL Adjustment: Adjust TC1001 for zero beat at specified frequency.
Receiver Alignment: Adjust L1001, L1002 for maximum sensitivity.
Transmitter Alignment: Adjust L2001, L2002 for maximum power output.
Modulation Adjustment: Set deviation using R3012.
Squelch Adjustment: Set squelch threshold using R1012.

Voltage Measurements

DC voltage measurements at key test points with 13.8V supply.

Test Point	Voltage (Rx)	Voltage (Tx)
IC1 Pin 8 (VCC)	+5.0V	+5.0V
Q1 Collector	+8.2V	+8.2V
Q2 Collector	+13.8V	+13.8V
IC2 Pin 5	+4.5V	+4.5V
Final Collector	+0.1V	+13.8V

Troubleshooting Guide

Common problems and their solutions.

Symptom	Possible Cause	Corrective Action
No power	Power cable, fuse F1	Check power connections; replace 15A fuse if blown
No transmit	PTT circuit, final transistor	Check PTT switch; test Q3 (2SC3102)
No receive	RF section, audio IC	Check Q1, Q2; test IC2 (TA7368F)
Low power output	PA bias, matching circuit	Adjust L2001, L2002; check bias voltage
Frequency error	PLL circuit, reference osc	Adjust TC1001; check X1 (12.8MHz)

Parts List

Critical replacement components and their part numbers.

Final Transistor: 2SC3102 (Original Kenwood)
Driver Transistor: 2SC3357
PLL IC: MB15E03SL
Audio IC: TA7368F
Main Fuse: 15A
Ceramic Filters: SFG10.7MS (CF1, CF2, CF3)
Crystals: X1: 12.8MHz, X2: 21.4MHz

Schematic Diagrams

Reference to complete schematic diagrams included in full service manual.

Complete schematic diagrams are provided in the full PDF service manual covering:

Main RF Circuit Board
Front Panel Control Board
Power Supply Section
Audio Circuit
PLL Synthesizer

Note: Schematics show component values, test points, and interconnection details.

Mechanical Information

Physical dimensions, mounting requirements, and mechanical specifications.

Mounting: Standard mobile bracket (OPC-599 optional)
Weight: 1.2 kg
Connectors: SO-239 antenna, 3-pin power, 6-pin microphone
Cooling: Aluminum heat sink with forced air cooling
Display: LCD with green backlight

Service Notes

Important service information and technical updates.

Firmware Updates: Available through Kenwood service centers for enhanced features and bug fixes.

Warranty Information: One year limited warranty from date of purchase. Service by unauthorized personnel voids warranty.

Service Centers: Authorized Kenwood service centers provide genuine parts and factory-trained technicians.

Technical Support: Contact Kenwood technical support for complex service issues.