Marantz SR-66 Service Manual

The Marantz SR-66 is a high-performance stereo receiver featuring advanced audio processing, multiple input/output options, and professional-grade amplification. This service manual provides comprehensive technical information for qualified service personnel, including schematics, alignment procedures, troubleshooting guides, and replacement parts lists for proper maintenance and repair.

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

Technical Specifications

Complete electrical and mechanical specifications for the Marantz SR-66 stereo receiver.

Parameter	Specification
Power Output	100W per channel (8Ω, 20Hz-20kHz)
Total Harmonic Distortion	<0.05% at rated output
Frequency Response	10Hz-100kHz (+0/-3dB)
Signal-to-Noise Ratio	>100dB (line inputs)
Input Sensitivity	200mV (line), 2.5mV (phono)
Input Impedance	47kΩ (line), 47kΩ/100pF (phono)
Damping Factor	>100 at 8Ω
Power Consumption	450W maximum
Dimensions	440mm × 150mm × 400mm (W×H×D)
Weight	12.5kg

Block Diagrams

System block diagrams showing signal flow and functional relationships between circuit sections.

Main System Block Diagram: Overview of complete receiver architecture
Preamplifier Section: Input selection, tone control, and volume control circuits
Power Amplifier Section: Final amplification stage and protection circuits
Power Supply Section: Transformer, rectification, and regulation circuits
Tuner Section: RF, IF, and demodulation circuits (if applicable)

NOTE: Refer to schematics for detailed component-level information.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Input Selector Circuit: Switching between multiple audio sources
Phono Equalizer: RIAA equalization for magnetic cartridges
Tone Control Circuit: Bass and treble adjustment networks
Volume/Balance Control: Precision attenuator circuits
Power Amplifier: Complementary symmetry output stage
Protection Circuit: DC detection, overload, and thermal protection
Power Supply: Dual rail supply with regulation

CAUTION! High voltages present - discharge power supply capacitors before servicing.

Alignment Procedures

Step-by-step alignment instructions for optimal performance.

DC Offset Adjustment: Adjust VR501/VR502 for 0mV output
Bias Current Adjustment: Set idle current to 20mA using VR503/VR504
Phono Equalization: Verify RIAA response using test equipment
Input Level Matching: Adjust input sensitivity for uniform response
Protection Circuit Test: Verify proper operation of safety circuits

Disassembly Instructions

Proper disassembly sequence to access internal components.

Remove top cover: Remove 6 screws from rear and sides
Remove front panel: Detach knobs and remove 4 mounting screws
Access main board: Remove shield covers and connector restraints
Remove power supply: Disconnect all wiring and remove mounting hardware
Access output transistors: Remove heat sink assembly

WARNING! Always disconnect AC power before disassembly.

Troubleshooting Guide

Systematic approach to diagnosing and repairing common issues.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check F501/F502; verify switch continuity; test transformer primary
No audio output	Protection circuit, amplifier stage	Check protection relay; test output transistors; verify supply voltages
Distorted audio	Bias current, damaged components	Adjust bias; test driver/output transistors; check electrolytic capacitors
Hum/buzz	Grounding, power supply	Verify ground connections; test filter capacitors; check rectifier diodes
Intermittent operation	Cold solder joints, connectors	Inspect solder joints; clean connectors; check for cracked traces

Replacement Parts List

Authorized replacement components with manufacturer part numbers.

Component	Part Number	Description
Output Transistors	2SC3281/2SA1302	Complementary power transistors
Main Fuses	F501/F502	5A 250V time-delay fuses
Power Transformer	T001	Custom wound 300VA transformer
Main Filter Caps	C701/C702	10,000μF 63V electrolytic
Relay	RY501	Protection relay 24VDC

PCB Layouts

Printed circuit board layouts for main board, power supply, and control sections.

Main Amplifier Board: Component placement and trace routing
Power Supply Board: High current traces and component locations
Control Board: Front panel switches and indicator circuits
Grounding Scheme: Star grounding points and signal return paths

NOTE: Use exact replacement components to maintain performance specifications.

Wiring Diagrams

Complete interconnecting wiring diagrams and cable routing.

Front Panel Wiring: Switch, indicator, and control connections
Power Supply Wiring: Transformer, rectifier, and filter connections
Input/Output Wiring: RCA jacks, speaker terminals, and ground connections
Internal Harnesses: Cable routing and connector pinouts

Safety Precautions

Essential safety procedures for service personnel.

Always disconnect AC power before servicing. Use isolation transformer when working on live circuits. Discharge large capacitors before testing. Use appropriate personal protective equipment. Follow electrostatic discharge (ESD) precautions when handling semiconductors.

DANGER! Lethal voltages present - qualified personnel only.

Service Notes

Important service tips and manufacturer updates.

Service Bulletin	Date	Description
SB-66-001	03/15/1998	Updated output transistor mounting procedure
SB-66-002	06/22/1999	Improved thermal compound application
SB-66-003	11/08/2000	Revised bias adjustment procedure
SB-66-004	02/14/2002	Protection circuit timing modification

Service Support: Contact Marantz technical support for latest service information.