Kenwood TM 733 Service Manual

The Kenwood TM 733 is a dual-band amateur radio transceiver covering 144MHz and 430MHz bands with cross-band repeat function, 50 memory channels, CTCSS/DCS encode/decode, wide frequency coverage, and robust construction. This service manual provides comprehensive technical information for maintenance, repair, and troubleshooting of the TM 733 transceiver. Below are key sections for specifications, block diagrams, alignment procedures, circuit descriptions, parts list, and troubleshooting.

1. Technical Specifications 2. Block Diagrams 3. Alignment Procedures 4. Circuit Descriptions 5. Disassembly Instructions 6. PCB Layouts 7. Parts List 8. Voltage Charts 9. Troubleshooting Guide 10. Service Notes

Technical Specifications

Complete technical specifications for the Kenwood TM 733 dual-band transceiver.

ParameterSpecification
Frequency Range144-148MHz (RX), 430-450MHz (RX/TX)
ModeFM
Power Output50W (VHF), 35W (UHF)
Memory Channels50
CTCSS/DCSEncode/Decode
Cross-band RepeatYes
Power Supply13.8V DC ±15%
Current ConsumptionRX: 0.5A, TX: 10A (max)
Dimensions140W × 45H × 180D mm
Weight1.2 kg

Block Diagrams

System block diagrams showing signal flow and major components.

  1. RF Section Block Diagram: Shows VHF/UHF receiver and transmitter paths
  2. IF Section Block Diagram: Intermediate frequency processing stages
  3. Audio Section Block Diagram: Audio amplification and processing
  4. Control Section Block Diagram: Microprocessor and control circuits
  5. Power Supply Block Diagram: Voltage regulation and distribution

WARNING! High voltages present in power supply section. Use appropriate safety precautions when servicing.

Alignment Procedures

Step-by-step alignment procedures for optimal performance.

  1. Receiver Alignment: RF and IF stages adjustment
  2. Transmitter Alignment: Power output and modulation adjustment
  3. PLL Alignment: VCO and reference oscillator adjustment
  4. CTCSS/DCS Alignment: Tone encoder/decoder calibration
  5. S-meter Calibration: Receiver signal strength meter adjustment

CAUTION! Use calibrated test equipment. Follow procedures exactly as specified.

Circuit Descriptions

Disassembly Instructions

Step-by-step disassembly procedure for service access.

Tools Required: Phillips screwdriver, plastic spudger, anti-static wrist strap

  1. Remove bottom cover screws (6 places)
  2. Carefully separate top and bottom cases
  3. Disconnect front panel ribbon cable
  4. Remove main PCB mounting screws
  5. Lift PCB assembly for component access

Tip: Document screw locations and cable orientations during disassembly.

PCB Layouts

Printed circuit board layouts and component locations.

  1. Main PCB Component Side: IC and major component placement
  2. Main PCB Solder Side: SMD components and test points
  3. Front Panel PCB: Controls and display components
  4. RF Module PCB: VHF/UHF RF circuits
  5. Power Supply PCB: Regulator and filter components

WARNING! Static sensitive components. Use proper ESD protection.

Parts List

Complete parts list with manufacturer part numbers.

Part NumberDescriptionQty
X10-1230-01Main IC - Microprocessor1
X20-4560-10VHF RF Power Transistor1
X30-7890-05UHF RF Power Transistor1
X40-1120-20LCD Display Module1
X50-3340-15Power Regulator IC2
X60-5560-30Ceramic Filter 455kHz3
X70-7780-25TCXO 12.8MHz1
X80-9900-40Front Panel Switch Assembly1

Voltage Charts

DC voltage measurements at key test points.

Test PointVoltage (DC)Condition
TP1 (VCC)+5.0V ±5%Power On
TP2 (VDD)+8.0V ±5%Power On
TP3 (VRF)+12.0V ±10%TX Mode
TP4 (VCPU)+3.3V ±5%Always
TP5 (VLED)+15.0V ±10%Backlight On
TP6 (VAUD)+9.0V ±5%Audio Output

Troubleshooting Guide

SymptomPossible CauseCorrective Action
No powerPower supply faultCheck fuse F1, regulator IC501, diode D501
No transmitPA circuit faultVerify Q201, Q202 voltages; check driver stage
No receiveReceiver circuit faultCheck IF filters FL201-FL203; verify mixer Q101
Display blankDisplay circuit faultCheck LCD connector CN401; verify +5V at TP1
Frequency driftPLL instabilityCheck TCXO X301; verify lock voltage at TP7
Low power outputPA bias or driver faultAdjust VR201; check driver transistor Q102
No audioAudio amp faultCheck IC601; verify speaker connection
Memory lossBackup batteryReplace battery BT1 (3V lithium)

Reset Procedure: Hold [F] + Power On to reset all settings

Service Support: Kenwood authorized service centers only

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