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Kenwood TM-271A - Service Manual

Kenwood TM-271A
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© 2003-10 PRINTED IN JAPAN
B51-8663-00
(
N
)
743
VHF FM TRANSCEIVER
TM-271A/271E
SERVICE MANUAL
CIRCUIT DESCRIPTION ............................ 2
SEMICONDUCTOR DATA ........................ 8
COMPONENTS DESCRIPTION ................ 9
PARTS LIST ............................................. 10
EXPLODED VIEW.................................... 17
PACKING ................................................. 18
RESETTING THE TRANSCEIVER ........... 19
ADJUSTMENT ........................................ 20
TERMINAL FUNCTION ........................... 27
PC BOARD
DISPLAY UNIT (X54-3450-10) ............ 28
TX-RX UNIT (X57-685X-XX)............... 30
SCHEMATIC DIAGRAM.......................... 34
BLOCK DIAGRAM ................................... 38
LEVEL DIAGRAM .................................... 40
SPECIFICATION ................... BACK COVER
CONTENTS
Microphone
(T91-0624-05)
Cabinet
(A01-2193-01)
Panel assy
(A62-1088-03)
Knob (Encoder)
(K29-9293-03)
Knob (Volume)
(K29-9292-03)
Key top
(K29-9291-01)
Microphone
(T91-0641-05)
Cabinet
(A01-2193-01)
Panel assy
(A62-1088-03)
Knob (Encoder)
(K29-9293-03)
Knob (Volume)
(K29-9292-03)
Key top
(K29-9291-01)
TM-271A (M2,M4)
TM-271A/E (K,M3,E)

Table of Contents

Other manuals for Kenwood TM-271A

Preview: Instruction Manual
Instruction Manual80 pages

Questions and Answers

  • V
    vsullivanJul 26, 2025
    What to do if my Kenwood TM-271A Transceiver won't transmit when I press Mic [PTT]?
    • C
      Christine RichardsJul 26, 2025
      If your Kenwood Transceiver won't transmit when you press the Mic [PTT] button, there might be a few reasons: * Ensure the microphone plug is fully inserted into the front panel connector until you hear the locking tab click. Always switch off the power before doing this. * Check if you've selected a transmit offset that's placing your transmit frequency outside the allowed range. To fix this, press [F], then [MENU], and use the Tuning control to go to Menu No. 5 (SFT). Press [MENU] again and use the Tuning control to select “OFF”. Store this setting by pressing [MENU], and then press any key (except [MENU]) to leave Menu Mode. * If you're using an external TNC, make sure it has finished transmitting before you press the Mic[PTT] button.
  • R
    Richard MyersJul 31, 2025
    Why won't my Kenwood TM-271A power on?
    • E
      erin50Jul 31, 2025
      If your Kenwood Transceiver won't power up, and nothing is showing on the display after you've connected the 13.8 V DC power supply and pressed the power switch, here's what to check: * Make sure the power cable is connected correctly, with the red wire to the positive (+) terminal and the black wire to the negative (–) terminal. * Inspect the power cable fuses. If any are open, find out what caused them to blow. After fixing any issues, replace the blown fuse(s) with new ones that have the same ratings.
  • J
    Jeffrey ThompsonAug 5, 2025
    What to do if frequency cannot be selected on Kenwood Transceiver?
    • M
      Maureen CrossAug 5, 2025
      If you can't select a frequency on your Kenwood Transceiver by turning the Tuning control or pressing Mic[UP]/[DWN], it might be because Memory Recall was selected. Try pressing VF.
  • J
    joneswhitneyAug 10, 2025
    How to unlock buttons on Kenwood Transceiver?
    • C
      Curtis JonesAug 10, 2025
      If most buttons/keys and the Tuning control on your Kenwood Transceiver aren't working, it could be because one of the Lock functions is turned ON. Try unlocking all of the Lock functions. Alternatively, the transceiver might be in Channel Display mode. To exit this mode, switch the transceiver power OFF, then press the Power and REV keys together.
  • E
    erin27Aug 15, 2025
    Why is my Kenwood Transceiver display too dim?
    • B
      Brandon HughesAug 15, 2025
      If the display on your Kenwood Transceiver is too dim, even when you've set it to a high brightness level, the supply voltage might be too low. The required supply voltage is 13.8 V DC ± 15% (11.7 V to 15.8 V DC). If the input voltage is outside of this range, adjust your regulated power supply and/or check all power cable connections.
  • T
    Tara AyalaAug 20, 2025
    Why can't I select memory channels on my Kenwood TM-271A Transceiver?
    • S
      Scott JensenAug 21, 2025
      To resolve the issue where Memory Channels cannot be selected on your Kenwood Transceiver using the Tuning control or Mic[UP]/[DWN], ensure that you have stored data in some Memory Channels.

Summary

CIRCUIT DESCRIPTION

Frequency Configuration

Details the receiver's double conversion superheterodyne circuitry.

IF Amplifier

Explains the amplification and filtering of the first IF signal.

Receiver System

Overview of the receiver's superheterodyne architecture.

Front-end RF Amplifier

Explains signal path from antenna to first mixer.

First Mixer

Describes heterodyning with PLL signal and MCF filtering.

CIRCUIT DESCRIPTION

Wide;Narrow Switching Circuit

Describes CPU control of ceramic filters for reception modes.

Squelch Circuit

Details noise detection and CPU control for squelch function.

AF Signal System

Details the audio signal path from IF IC to speaker output.

PLL Frequency Synthesizer

Explains the PLL circuit for generating local oscillator and RF signals.

CIRCUIT DESCRIPTION

Unlock Circuit

Describes CPU monitoring of PLL lock status for transmission.

Transmitter System

Overview of the transmitter's signal generation and amplification.

CIRCUIT DESCRIPTION

Control Circuit

Explains CPU functions for controlling various circuits.

Memory Circuit

Describes the EEPROM for storing adjustment data.

Display Circuit

Details CPU control of the LCD and LEDs.

Key Matrix Circuit

Explains CPU detection of key presses via a matrix.

Encode

Describes DCS/CTCSS/DTMF signal processing and modulation.

CIRCUIT DESCRIPTION

Decode

Explains CTCSS/DCS and DTMF signal decoding processes.

D;A Converter

Details the D/A converter's role in adjusting various levels.

Power Supply Circuit

Explains how power is supplied, regulated, and protected.

Data Terminal and Peripheral Circuits

Describes data communication modes and peripheral signals.

CIRCUIT DESCRIPTION

Transmission Signals

Describes signal paths for 1200bps and 9600bps data transmission.

Reception Signals

Details reception signal paths for 9600bps and 1200bps data.

Squelch Signal Output Circuit

Explains squelch signal output to TNC for traffic prevention.

SEMICONDUCTOR DATA

Terminal Function

Lists pin functions for the Microprocessor (IC101).

COMPONENTS DESCRIPTION

Display Unit Components

Lists components used in the display unit.

TX-RX Unit Components

Lists components used in the TX-RX unit.

PARTS LIST

TM-271 A;E Model Parts

Lists parts specific to the TM-271A/E models.

Display Unit Parts

Lists parts for the display unit.

PARTS LIST

TX-RX Unit Parts

Lists parts for the TX-RX unit.

EXPLODED VIEW

PACKING

RESETTING THE TRANSCEIVER

Initial Settings

Describes default frequencies and settings after a reset.

Full Reset Procedure

Details methods for resetting all transceiver parameters to factory defaults.

VFO Reset Procedure

Details methods for resetting VFO parameters to factory defaults.

ADJUSTMENT

Adjustment Mode Overview

Overview of entering and using the adjustment mode.

Panel Key Operation in Adjustment Mode

Details key operations for adjusting settings in the mode.

ADJUSTMENT

Adjustment Items and Test Frequencies

Lists adjustable items, display values, and test frequencies.

ADJUSTMENT

Test Equipment for Alignment

Lists necessary test equipment and their specifications for alignment.

ADJUSTMENT

Adjustment Point Locations

Shows specific locations for adjustment points on the PCB.

Adjustment Notes

Important notes regarding EEPROM and AF PA adjustments.

ADJUSTMENT

PCB Section Adjustments

Details specific adjustments for the PCB section.

Transmitter Section Adjustments

Details specific adjustments for the transmitter section.

ADJUSTMENT

MAX Deviation Adjustment

Adjustment procedure for maximum deviation settings.

MIC Sensitivity Adjustment

Adjustment procedure for microphone sensitivity.

CTCSS Fine Deviation Adjustment

Adjustment procedure for CTCSS fine deviation settings.

DCS Fine Deviation Adjustment

Adjustment procedure for DCS fine deviation settings.

DTMF Fine Deviation Adjustment

Adjustment procedure for DTMF fine deviation settings.

Receiver Section Adjustments

Details specific adjustments for the receiver section.

ADJUSTMENT

Squelch Tightness Adjustment

Adjustment procedure for squelch tightness settings.

Squelch Open Adjustment

Adjustment procedure for squelch opening settings.

RSSI Writing Procedure

Procedure for writing RSSI values.

S-meter S1 Level Adjustment

Adjustment procedure for S-meter S1 level.

S-meter Full Scale Adjustment

Adjustment procedure for S-meter full scale.

TERMINAL FUNCTION

TX-RX Unit Terminal Functions

Lists pin functions for the TX-RX unit.

Display Unit Terminal Functions

Lists pin functions for the display unit.

PC BOARD LAYOUT

Display Unit Component Side View

Component layout for the display unit (component side).

Display Unit Foil Side View

Component layout for the display unit (foil side).

PC BOARD LAYOUT

TX-RX Unit Component Side View

Component layout for the TX-RX unit (component side).

TX-RX Unit Foil Side View

Component layout for the TX-RX unit (foil side).

SCHEMATIC DIAGRAM - TX-RX Unit

TX-RX Unit Schematic

Provides the schematic diagram for the TX-RX unit.

SCHEMATIC DIAGRAM - Display Unit

Display Unit Schematic

Provides the schematic diagram for the display unit.

BLOCK DIAGRAM

LEVEL DIAGRAM

Receiver Section Levels

Details signal levels in the receiver section for performance checks.

Transmitter Section Levels

Details signal levels in the transmitter section for performance checks.

Kenwood TM-271A Specifications

General IconGeneral
Frequency Range144-148 MHz
ModeFM
Antenna Impedance50 Ω
Channels200
Weight1.3 kg
Voltage13.8 V DC

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