Marantz SR4500 Service Manual

The Marantz SR4500 is a high-performance AV receiver featuring Dolby Digital and DTS decoding, 6-channel amplification with 100W per channel, multiple audio/video inputs, digital optical and coaxial inputs, AM/FM tuner, and advanced surround sound processing. This service manual provides technical specifications, circuit diagrams, troubleshooting procedures, and maintenance guidelines for qualified service technicians.

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

Technical Specifications

Complete technical specifications and performance characteristics of the Marantz SR4500 AV receiver.

Parameter	Specification
Power Output	100W x 6 channels (8Ω, 20Hz-20kHz, 0.08% THD)
Frequency Response	10Hz-100kHz (+1/-3dB)
Total Harmonic Distortion	0.08% (20Hz-20kHz at rated power)
Signal-to-Noise Ratio	100dB (line input)
Input Sensitivity	200mV (line), 2.5mV (MM phono)
Digital Inputs	Optical x2, Coaxial x2
Video Inputs	Composite x4, S-Video x4
Audio Inputs	Line x6, Phono, Tape
Outputs	6-channel pre-out, tape out, subwoofer
Dimensions	440 x 161 x 418mm (WxHxD)
Weight	12.5kg
Power Consumption	550W maximum

Block Diagrams

System block diagrams showing signal flow and functional relationships between major components.

Main System Block Diagram - Overall signal processing flow
Power Supply Block Diagram - AC/DC conversion and distribution
Audio Processing Block Diagram - Digital decoding and analog processing
Video Processing Block Diagram - Video switching and processing
Tuner Section Block Diagram - AM/FM reception and processing
Control System Block Diagram - Microprocessor and user interface

NOTE: Refer to schematic diagrams for detailed circuit information.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Power Supply Circuit: Switching power supply with multiple regulated outputs (+12V, +5V, ±15V)
Main Amplifier Circuit: 6-channel discrete power amplifier with protection circuitry
Digital Audio Processor: 24-bit/96kHz DAC with Dolby Digital and DTS decoding
Video Switching Circuit: Composite and S-Video switching with buffering
Tuner Circuit: PLL synthesized AM/FM tuner with quartz filtering
Control Circuit: 8-bit microcontroller with front panel and remote control interface
Protection Circuit: DC detection, overcurrent, and thermal protection

Disassembly Procedures

Step-by-step instructions for disassembling the unit for service access.

Remove Top Cover: Remove 6 screws from rear panel and 2 screws from each side
Remove Front Panel: Disconnect ribbon cables and remove 4 screws
Remove Main Board: Disconnect all connectors and remove 8 mounting screws
Remove Power Supply: Disconnect AC input and remove 4 mounting screws
Remove Amplifier Heat Sink: Remove thermal compound and 6 mounting screws
Access Tuner Section: Remove shield cover and tuner mounting bracket

WARNING! Disconnect AC power before disassembly. Discharge large capacitors.

Test and Adjustment

Factory test procedures and adjustment points for proper calibration.

Test Point	Procedure	Specification
DC Offset	Measure output terminals with no signal	±50mV maximum
Bias Current	Adjust VR501-VR506 for 20mA	20mA ±2mA
Power Output	1kHz sine wave at 0.08% THD	100W ±5% per channel
Frequency Response	20Hz-20kHz sweep	±1dB from reference
Tuner Sensitivity	FM 98MHz at 30dB S/N	12.8dBf typical
Digital Lock	Apply 48kHz digital signal	Stable lock within 2 seconds

Troubleshooting Guide

Common symptoms, probable causes, and corrective actions.

Symptom	Probable Cause	Corrective Action
No power	Fuse blown, power supply fault	Check F001, test Q801-Q804, check D801-D808
No audio output	Protection circuit, mute circuit	Check protection relay, test mute transistors
Distorted audio	Amplifier bias, damaged output transistors	Adjust bias, test Q601-Q606, check drivers
No digital processing	Digital board power, clock circuit	Check IC901 power, test X901 (16.9344MHz)
Tuner not working	Tuner power, PLL circuit	Check tuner supply voltages, test IC701
No video output	Video IC failure, switching problem	Test IC401 video switch, check video buffers
Display issues	Display driver, microcontroller	Test display voltages, check IC101 microcontroller

Parts List

Complete list of components with part numbers and specifications.

Main ICs: IC901 - Digital Audio Processor (MN67740MH), IC101 - Microcontroller (HD6437043F20), IC701 - Tuner (LA1266)
Power Transistors: Q601-Q606 - 2SC5200/2SA1943 output pairs
Power Supply: Q801-Q804 - 2SK3562 switching transistors, D801-D808 - rectifier diodes
Capacitors: C801 - 680μF/450V main filter, C601-C606 - 470μF/63V output coupling
Resistors: R601-R606 - 0.22Ω/5W emitter resistors
Fuses: F001 - 6.3A/250V AC input fuse
Transformers: T801 - Main switching transformer

PCB Layouts

Printed circuit board layouts for all major assemblies.

Main Board - Component side and solder side views
Power Supply Board - Complete layout with component designations
Front Panel Board - Display and control interface layout
Digital Board - DSP and digital interface section
Tuner Board - AM/FM tuner circuit layout
Amplifier Board - Power amplifier and protection circuits

NOTE: All layouts include component designations matching schematic diagrams.

Wiring Diagrams

Interconnection diagrams showing cable routing and connector pinouts.

Main Harness: Power supply to main board connections
Front Panel Harness: Microcontroller to display and controls
Speaker Outputs: Amplifier to terminal block wiring
Input/Output Connectors: Rear panel audio/video connections
Power Cord: AC input wiring and grounding
Internal Cables: Inter-board ribbon cables and shielded wires

Safety Precautions

Important safety information for service technicians.

Always disconnect AC power before servicing
Use isolation transformer when testing live circuits
Discharge large capacitors before handling
Use appropriate personal protective equipment
Follow electrostatic discharge (ESD) precautions
Verify all safety certifications after repair
Test ground continuity and insulation resistance
Ensure proper reassembly and secure mounting

DANGER! Lethal voltages present. Only qualified technicians should perform service.

Service Notes

Additional technical information and service tips.

Factory Reset: Hold TUNER PRESET + SURROUND MODE while powering on
Service Mode: Press TONE + SURROUND MODE + DIMMER simultaneously
Firmware Update: Requires special interface cable and software
Common Failures: Output transistors, power supply ICs, display drivers
Test Equipment: Oscilloscope, DMM, audio generator, dummy loads required
Warranty: Original warranty void if serviced by unauthorized personnel
Support: Contact Marantz technical support for schematic updates