Marantz SR4400 Service Manual

The Marantz SR4400 is a high-performance AV receiver featuring Dolby Digital and DTS decoding, 6-channel amplification (100W per channel), multiple audio/video inputs, digital optical/coaxial inputs, AM/FM tuner, preamp outputs, speaker A/B switching, and advanced DSP sound modes. This service manual provides technical specifications, schematics, troubleshooting guides, and repair procedures for qualified service technicians.

Technical Specifications

Complete technical specifications and performance characteristics of the Marantz SR4400 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), 800mV (digital)
Digital Inputs	2 optical, 2 coaxial
Analog Inputs	6 line-level, phono MM
Video Inputs	3 composite, 2 S-Video
Outputs	6-channel preamp, composite video, S-Video
Power Consumption	550W maximum

Block Diagrams

System block diagrams showing signal flow and functional relationships between circuits.

1. Main System Block Diagram: Overall signal routing and processing
2. Power Supply Block Diagram: AC input to DC distribution
3. Audio Processing Block: Digital decoding and analog processing
4. Video Switching Block: Input selection and output routing
5. Control System Block: Microprocessor and interface circuits

WARNING! High voltages present in power supply section. Disconnect AC power before servicing.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

1. Power Supply Circuit: Switching power supply with multiple voltage rails
2. Main Amplifier Circuit: 6-channel discrete power amplifier design
3. Digital Audio Processor: Dolby Digital/DTS decoder IC and support circuits
4. Video Switching Circuit: Composite and S-Video routing ICs
5. Microprocessor Control: Main system controller and display driver
6. Tuner Section: AM/FM tuner with PLL synthesis

CAUTION! Static-sensitive components present. Use proper ESD precautions.

Disassembly Procedures

• Top Cover Removal: Remove 6 screws from rear panel and sides
• Front Panel Removal: Disconnect ribbon cables and remove 4 screws
• Main Board Access: Remove shield and disconnect all connectors
• Power Supply Board: Discharge capacitors before servicing
• Amplifier Heat sink: Thermal compound replacement procedure
• Tuner Module: Special alignment tools required
• Display Assembly: Fluorescent display handling precautions

Alignment & Adjustment

Factory alignment procedures and test equipment requirements.

Required Equipment: Audio generator, oscilloscope, distortion analyzer, multimeter, dummy loads

DC Offset Adjustment: Adjust VR601-VR606 for 0mV ±5mV at speaker terminals

Bias Current Adjustment: Set VR701-VR706 for 20mA ±2mA across emitter resistors

Tuner Alignment: FM/AM IF and RF alignment using specified test points

DSP Calibration: Digital processor initialization and factory reset procedures

Test Points & Voltages

Critical test point locations and expected voltage measurements.

Test Point	Location	Normal Voltage
TP1 (+12V)	Power supply board	+12V ±0.5V
TP2 (+5V)	Digital board	+5V ±0.1V
TP3 (+35V)	Amplifier section	+35V ±2V
TP4 (-35V)	Amplifier section	-35V ±2V
TP5 (OSC OUT)	Crystal oscillator	2.5V p-p
TP6 (REF)	Voltage reference	2.5V ±0.05V

Parts List

Complete component listing with manufacturer part numbers.

1. Semiconductors: Transistors, ICs, diodes with original part numbers
2. Passive Components: Resistors, capacitors, inductors values and tolerances
3. Electromechanical: Relays, switches, connectors, fuses
4. Mechanical Parts: Screws, brackets, knobs, panels
5. PCB Assemblies: Complete board part numbers

Tip: Use only Marantz-approved replacement parts for warranty service.

PCB Layouts

Printed circuit board layouts and component location diagrams.

1. Main Board: Component side and solder side views
2. Power Supply Board: High-voltage section clearly marked
3. Front Panel Board: Display and control circuits
4. Amplifier Board: Output transistors and bias circuits
5. Tuner Module: RF and IF section layouts

WARNING! Observe polarity markings for electrolytic capacitors.

Troubleshooting Flowcharts

Systematic diagnostic procedures for common failure modes.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power supply	Check F901 (5A), test Q901-Q904
No audio output	Protection circuit	Check relay RL601, DC offset
Distorted sound	Amplifier bias	Adjust bias current, test output transistors	No display	Display driver	Check -30V supply, IC701 display driver
Remote not working	IR receiver	Test IR901, check 5V supply to receiver module

Reset Procedure: Hold TUNER PRESET + and - while powering on

Safety Precautions

Essential safety information for service personnel.

Always disconnect AC power before servicing. Discharge large capacitors. Use isolation transformer when testing live circuits. Follow ESD protection procedures. Note that some components have special safety requirements.

CAUTION! High temperatures on heat sinks during operation. Allow to cool before servicing.

Service Notes

Important service information and common repair issues.

• Factory service mode access procedure
• Software version identification
• Common failure components and recommended replacements
• Warranty service documentation requirements
• Authorized service center contact information

Service Support: Marantz Service Department - 1-800-654-6633

Technical Website: www.marantz.com/service