Kenwood KA 5500 Service Manual

The Kenwood KA 5500 is a high-performance stereo integrated amplifier featuring 60 watts per channel RMS, direct-coupled output circuitry, phono equalizer with MM/MC cartridge compatibility, tone controls with defeat switch, loudness contour, two tape monitor loops, and speaker A/B switching. Below are key sections for technical specifications, circuit description, adjustment procedures, troubleshooting, and schematics.

1. Technical Specifications 2. Block Diagram & Circuit Description 3. Adjustment Procedures 4. Disassembly Instructions 5. Troubleshooting Guide 6. Schematic Diagrams 7. Parts List 8. PCB Layouts 9. Waveform Charts 10. Service Notes 11. Safety Precautions

Technical Specifications

Complete electrical and mechanical specifications for the Kenwood KA 5500 integrated amplifier.

ParameterSpecification
Power Output60W + 60W RMS (8Ω, 20Hz-20kHz)
Total Harmonic Distortion0.02% (rated power)
Frequency Response5Hz-100kHz (+0, -3dB)
Input SensitivityPhono: 2.5mV, Aux: 150mV, Tape: 150mV
Signal-to-Noise RatioPhono: 80dB, Aux: 100dB
Tone ControlsBass: ±10dB at 100Hz, Treble: ±10dB at 10kHz
Power SupplyAC 120V/220V/240V, 50/60Hz
Dimensions440W × 145H × 355D mm
Weight11.5 kg
SemiconductorsTransistors: 78, Diodes: 51, ICs: 3

Block Diagram & Circuit Description

Detailed explanation of the amplifier's circuit topology and signal flow.

  1. Power Supply Section: Transformer, rectifiers, and filter capacitors providing ±45V DC rails.
  2. Preamplifier Stage: Phono equalizer, tone control, and selector switching circuits.
  3. Power Amplifier Section: Direct-coupled complementary symmetry output stage.
  4. Protection Circuitry: DC detection, overload protection, and thermal shutdown.
  5. Control Circuits: Input selector, tape monitor, loudness, and muting functions.

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

Adjustment Procedures

Step-by-step calibration and alignment instructions for optimal performance.

  1. DC Offset Adjustment: Adjust VR501/502 for 0mV ±5mV at speaker terminals.
  2. Bias Current Adjustment: Set VR503/504 for 20mA across emitter resistors.
  3. Phono Equalization: Verify RIAA response using test records and oscilloscope.
  4. Meter Calibration: Adjust meter circuit for accurate power level indication.

CAUTION! Use isolation transformer when making live measurements.

Disassembly Instructions

Troubleshooting Guide

Systematic approach to diagnosing and repairing common issues.

Test Equipment Required: Multimeter, oscilloscope, audio generator, dummy loads.

SymptomPossible CauseCorrective Action
No powerFuse blown, power switch, transformerCheck F601/F602 fuses; test power switch; verify transformer output.
Distorted outputBias current, output transistorsAdjust bias current; test/output transistors Q501-Q504.
DC offset highInput differential pair, feedback circuitCheck Q401/Q402; measure feedback network R415-R418.
No phono signalPhono EQ circuit, selector switchTest phono stage Q301-Q306; clean selector switch.
Hum/buzzGrounding, filter capacitorsCheck ground connections; test main filter capacitors C601/C602.

Schematic Diagrams

Complete circuit schematics for all amplifier sections.

  1. Main Amplifier Circuit: Power amplifier and driver stages.
  2. Preamplifier Section: Phono equalizer and tone control circuits.
  3. Power Supply: Transformer, rectification, and regulation.
  4. Protection Circuit: DC detection and relay drive.
  5. Control Circuits: Input selection, tape monitor, and muting.

Tip: Use schematic reference numbers when ordering replacement parts.

Parts List

Comprehensive listing of all components with manufacturer part numbers.

ReferenceDescriptionPart Number
Q501-Q504Output Transistor 2SC2581/2SA11062SC2581-O/2SA1106-O
Q401-Q404Driver Transistor 2SC2344/2SA10112SC2344-Y/2SA1011-Y
C601/C602Main Filter Capacitor 10000μF/63VECA-2AH103
IC301Phono Equalizer IC μPC4570μPC4570C
F601/F602Main Fuse 4A/250VAGC-4
RL601Protection Relay MY4-02-DC24MY4-02-DC24

PCB Layouts

Printed circuit board patterns and component placement guides.

  1. Main Amplifier Board: Component side and solder side views.
  2. Power Supply Board: High-current traces and component locations.
  3. Control PCB: Switch and potentiometer mounting details.
  4. Front Panel Board: Indicator lights and switch wiring.

WARNING! Observe correct polarity when replacing electrolytic capacitors.

Waveform Charts

Reference waveforms for key test points under various conditions.

Service Notes

Important technical bulletins and modification information.

Service Bulletin SB-5500-1: Improved thermal stability with bias circuit modification. Replace R435/R436 with 100Ω 1/2W metal film resistors. Service Bulletin SB-5500-2: Protection relay contact cleaning procedure for intermittent channel operation.

Safety Precautions

Essential safety procedures for technicians and service personnel.

HazardPrecautionProcedure
Electric ShockHigh voltage capacitorsDischarge all capacitors before servicing; use isolation transformer.
Heat DamageHot componentsAllow amplifier to cool before handling heat sinks and power transistors.
Component StressESD sensitive devicesUse grounded wrist strap when handling MOSFETs and ICs.
Fire HazardIncorrect fuse replacementReplace fuses with specified ratings only; investigate cause of failure.

Service Contacts: Kenwood Service Division: 1-800-536-9663; www.kenwood.com/service

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