Kenwood KA 7300 Service Manual

The Kenwood KA 7300 is a high-quality stereo integrated amplifier featuring 60 watts per channel RMS power output, dual power supply system, FET phono equalizer, loudness control, tone defeat, and high damping factor. This service manual provides comprehensive technical information for service technicians including schematics, alignment procedures, parts list, and troubleshooting guidelines.

1. Specifications 2. Block Diagram 3. Circuit Description 4. Disassembly Instructions 5. Adjustment Procedures 6. Schematic Diagrams 7. Parts List 8. PCB Layout 9. Troubleshooting Guide 10. Safety Precautions

Specifications

Technical specifications and performance characteristics of the Kenwood KA 7300 integrated amplifier.

Parameter	Specification
Power Output	60W + 60W RMS (8 ohms, 20Hz-20kHz)
Total Harmonic Distortion	0.02% (at rated output)
Frequency Response	5Hz - 100kHz (+0, -3dB)
Input Sensitivity	Phono: 2.5mV, Aux: 150mV, Tuner: 150mV
Signal-to-Noise Ratio	Phono: 80dB, Aux: 100dB
Damping Factor	70 (8 ohms, 1kHz)
Tone Controls	Bass: ±10dB at 100Hz, Treble: ±10dB at 10kHz
Power Requirements	AC 120V, 60Hz / 220V, 50Hz (switchable)
Dimensions	440 x 150 x 370mm (W x H x D)
Weight	12.5 kg

Block Diagram

System block diagram showing signal flow and major circuit sections.

Input Selector: Phono, Aux, Tuner inputs
Phono Equalizer: RIAA equalization with FET input
Tone Control: Bass and treble controls with defeat function
Volume/Loudness: Master volume with loudness compensation
Power Amplifier: Dual power supply, direct coupling
Protection Circuit: DC detection and relay protection
Power Supply: Dual transformer system

NOTE: Refer to schematic diagram for detailed circuit connections.

Circuit Description

Detailed explanation of major circuit sections and their operation.

Phono Equalizer: FET input stage for low noise, RIAA equalization network
Tone Control: Baxandall type tone control circuit
Power Amplifier: Complementary symmetry output stage with triple Darlington configuration
Protection Circuit: DC offset detection and speaker relay delay
Power Supply: Separate transformers for left and right channels

WARNING! High voltages present in power supply section. Exercise caution when servicing.

Disassembly Instructions

Step-by-step procedure for disassembling the amplifier for service.

Remove top cover: Unscrew 6 screws on top panel
Remove bottom cover: Unscrew 4 screws on bottom
Front panel removal: Remove knobs and unscrew front panel
PCB access: Remove relevant screws and carefully lift boards
Transformer removal: Disconnect wiring and remove mounting bolts

CAUTION! Label all wires and connections before disassembly.

Adjustment Procedures

Factory adjustment procedures and test points.

DC Offset: Adjust VR501/VR502 for 0mV ±5mV at speaker terminals
Bias Current: Adjust VR503/VR504 for 20mA across emitter resistors
Phono Balance: Adjust for equal output from both channels
Protection Delay: Verify 3-5 second delay before relay engagement

Schematic Diagrams

Complete schematic diagrams for all circuit sections.

Main Amplifier Section: Power amplifier, driver stage, and protection circuit
Pre-amplifier Section: Phono equalizer, tone control, and input selector
Power Supply Section: Dual transformer, rectifiers, and regulators
Control Section: Selector switches, volume control, and function switches

NOTE: All schematics include component values and test points.

Parts List

Complete parts list with manufacturer part numbers and substitutes.

Reference	Description	Part Number
Q1-Q4	2SC1775A Transistor	2SC1775A
Q5-Q8	2SA872A Transistor	2SA872A
Q9-Q12	2SC1919 Transistor	2SC1919
D1-D4	1S2473 Diode	1S2473
C1-C4	470μF 80V Capacitor	ECA-2AHG471
R1-R4	0.22Ω 5W Resistor	RS-5B.22J
F1,F2	4A Fuse	AGC-4

PCB Layout

Printed circuit board layouts and component placement diagrams.

Main Amplifier Board: Component side and solder side
Pre-amplifier Board: Component placement and routing
Power Supply Board: Transformer connections and rectifier layout
Control Board: Switch and potentiometer connections

Tip: Use exact replacement components for optimal performance.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Blown fuse, power switch	Check F1, F2 fuses; test power switch
No sound	Protection relay, broken wires	Check relay operation; inspect wiring
Distortion	Bias current, output transistors	Adjust bias; test output transistors
Hum noise	Grounding, filter capacitors	Check ground connections; replace capacitors
One channel dead	Preamp section, selector switch	Test preamp output; clean selector switch

Service Note: Always check DC offset and bias current after repairs.

Safety Precautions

Important safety information for service technicians.

Always disconnect power before servicing. Use isolation transformer when testing. High voltages are present in power supply section. Ensure proper grounding. Use correct replacement parts meeting original specifications.

WARNING! Lethal voltages present. Qualified technicians only.