Kenwood PS 30 Service Manual

The Kenwood PS 30 is a professional stereo power amplifier designed for high-fidelity audio applications. This service manual provides comprehensive technical information including specifications, circuit diagrams, alignment procedures, troubleshooting guides, and parts lists for qualified service technicians. Below are key sections covering technical specifications, block diagrams, adjustment procedures, disassembly instructions, and maintenance guidelines.

1. Technical Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Adjustment Procedures 5. Disassembly Instructions 6. Parts List 7. PCB Layouts 8. Troubleshooting Guide 9. Maintenance Schedule 10. Safety Precautions 11. Service Notes

Technical Specifications

Key performance parameters and electrical characteristics of the Kenwood PS 30 power amplifier.

Parameter	Specification
Power Output	30W + 30W RMS (8Ω, 20Hz-20kHz)
Total Harmonic Distortion	0.08% (at rated output)
Frequency Response	10Hz - 50kHz (+0/-1dB)
Input Sensitivity	150mV (for rated output)
Signal-to-Noise Ratio	90dB (IHF-A)
Damping Factor	40 (8Ω, 1kHz)
Power Supply	AC 120V/230V, 50/60Hz
Power Consumption	120W (max)
Dimensions	420(W) x 110(H) x 290(D) mm
Weight	6.5 kg

Block Diagrams

System block diagrams showing signal flow and power distribution.

Main System Block Diagram: Shows overall signal path from input to output stages.
Power Supply Block Diagram: Illustrates AC input, transformer, rectification, and regulation.
Amplifier Section: Detailed block diagram of left and right channel amplification.
Protection Circuit: Block diagram of overload and thermal protection systems.

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

Circuit Descriptions

Detailed explanations of major circuit sections and their operation.

Input Stage: Differential amplifier with current mirror load.
Voltage Amplification: High-gain voltage amplifier with frequency compensation.
Output Stage: Complementary symmetry push-pull configuration.
Power Supply: Dual rail supply with bridge rectifier and filter capacitors.
Protection Circuits: DC detection, overload, and thermal protection.

CAUTION! Always discharge large capacitors before working on power supply circuits.

Adjustment Procedures

DC Offset Adjustment: Adjust VR101/VR201 for 0V ±10mV at output terminals.
Bias Current Adjustment: Set VR102/VR202 for 20mA across emitter resistors.
Gain Matching: Verify channel balance within 0.5dB.
Protection Threshold: Check DC protection activates at ±2V DC output.
Power Supply Voltages: Verify ±35V DC rails within 5% tolerance.
Test Equipment Required: Oscilloscope, audio generator, DMM, dummy loads.
Test Conditions: 1kHz sine wave, 8Ω load, normal operating temperature.

Disassembly Instructions

Step-by-step guide for accessing internal components.

Procedure: Remove top cover screws, lift cover, disconnect internal wiring as needed.

Power off and unplug amplifier from AC outlet.
Remove 8 screws from top cover (4 front, 4 rear).
Lift cover straight up to avoid damaging internal components.
Document wiring connections before disassembly.
Use anti-static precautions when handling PCBs.

Tip: Take photos during disassembly to aid reassembly.

Parts List

Complete listing of components with manufacturer part numbers.

Reference	Description	Part Number
Q101-Q104	Transistor 2SC2240	KSC1845
Q105-Q108	Transistor 2SA970	KSA992
Q109,Q110	Driver Transistor 2SC2073	MJE15032
Q111,Q112	Driver Transistor 2SA940	MJE15033
Q113,Q114	Output Transistor 2SC2581	NJW3281
Q115,Q116	Output Transistor 2SA1106	NJW1302
C101,C201	Capacitor 1μF/50V	ECQ-V1H105JL
C107,C207	Capacitor 100pF/100V	CC45SL2DO101J
D101-D104	Diode 1S2473	1N4148
F101	Fuse 3A/250V	3AG-3

PCB Layouts

Printed circuit board layouts and component placement diagrams.

Main Amplifier Board: Component side and solder side views.
Power Supply Board: Layout showing rectifier and filter components.
Protection Circuit Board: Component placement and trace routing.
Input/Output Board: RCA connectors and speaker terminals.

WARNING! Observe polarity markings when replacing electrolytic capacitors.

Troubleshooting Guide

Systematic approach to diagnosing common problems.

Symptom	Possible Cause	Corrective Action
No output	Blown fuse, protection circuit	Check F101, measure output DC offset, test protection relay.
Distorted sound	Bias current, damaged output transistors	Adjust bias current, check output devices for shorts.
Hum/buzz	Ground loop, filter capacitors	Check ground connections, test power supply capacitors.
One channel dead	Open input, failed components	Signal trace from input, check transistors and resistors.
Overheating	Excessive bias, poor ventilation	Reset bias current, ensure adequate airflow.

Reset: Verify all adjustments after component replacement.

Maintenance Schedule

Recommended maintenance intervals and procedures.

Clean controls and connectors annually. Check bias current every 2 years. Replace electrolytic capacitors after 10 years of service.

CAUTION! Always disconnect from power before performing maintenance.

Safety Precautions

FCC Part 15: Class B digital device; complies with interference limits for residential use. Copyright © Kenwood Corporation. For technical support, contact authorized Kenwood service centers. Use only genuine Kenwood replacement parts.

Service Notes

Important notes for service technicians and calibration records.

Service Date	Technician	Work Performed	Test Results
MM/DD/YYYY	Technician Name	Description of service	Pass/Fail with measurements
MM/DD/YYYY	Technician Name	Description of service	Pass/Fail with measurements
MM/DD/YYYY	Technician Name	Description of service	Pass/Fail with measurements

Service Centers: Contact Kenwood authorized service network for genuine parts and technical support.