Marantz SR4021 Service Manual

The Marantz SR4021 is a high-performance audio/video receiver featuring Dolby Digital and DTS decoding, 5.1 channel amplification, multiple audio/video inputs, AM/FM tuner, remote control, and advanced audio processing. This service manual provides technical specifications, circuit diagrams, troubleshooting procedures, and repair instructions for qualified service technicians.

1. Technical Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Disassembly Procedures 5. Test Points & Measurements 6. Troubleshooting Flowcharts 7. Parts List & Replacement 8. Alignment Procedures 9. Safety Precautions 10. Schematics 11. Service Notes

Technical Specifications

Complete technical specifications for the Marantz SR4021 AV receiver.

Parameter	Specification
Power Output	70W per channel (8Ω, 20Hz-20kHz, 0.08% THD)
Total Harmonic Distortion	0.08% (20Hz-20kHz at 70W)
Frequency Response	10Hz-100kHz (+1/-3dB)
Signal-to-Noise Ratio	100dB (IHF-A)
Input Sensitivity	200mV (line inputs)
Surround Formats	Dolby Digital, DTS, Dolby Pro Logic II
Video Inputs	3 composite, 2 S-Video, 2 component
Audio Inputs	6 analog, 2 digital coaxial, 2 digital optical
Tuner Section	AM/FM with 30 station presets
Power Consumption	400W maximum

Block Diagrams

System block diagrams showing signal flow and functional relationships.

Main System Block Diagram: Overall signal processing flow
Power Supply Block Diagram: Voltage distribution and regulation
Audio Processing Block Diagram: DSP and amplification stages
Video Processing Block Diagram: Video switching and processing
Tuner Block Diagram: AM/FM reception and processing

WARNING! For qualified service personnel only. Do not attempt repairs without proper training.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Power Supply Circuit: Switching power supply with multiple voltage rails
Main Amplifier Circuit: 5-channel discrete power amplifier design
Digital Signal Processor: 24-bit/96kHz audio processing
Video Switching Circuit: High-quality video matrix switching
Microprocessor Control: System control and user interface
Tuner Circuit: PLL synthesized AM/FM tuner

CAUTION! High voltages present. Disconnect power before servicing.

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 Removal: Discharge capacitors and remove mounting screws
Amplifier Heat Sink: Remove thermal compound and mounting hardware
Tuner Module: Detach antenna connectors and mounting brackets

Test Points & Measurements

Critical test points and measurement procedures for proper alignment.

DC Voltage Measurements: +12V, +5V, +3.3V, ±15V rails. Audio Measurements: Frequency response, THD, signal-to-noise ratio. Video Measurements: Bandwidth, signal levels, impedance matching.

Test Equipment Required: Oscilloscope, audio analyzer, multimeter, signal generator, dummy loads.

Troubleshooting Flowcharts

Systematic troubleshooting procedures for common failure modes.

Symptom	Possible Cause	Corrective Action
No power	Power supply failure	Check fuse F001, diodes D001-D004, IC001
No audio output	Amplifier circuit	Test output transistors Q101-Q110, check protection circuit
Distorted audio	DC offset	Measure DC offset at speaker terminals, replace faulty components
No video	Video processor	Check IC301 video switching, test video inputs
Tuner not working	Tuner module	Verify +12V supply to tuner, check antenna connections

Parts List & Replacement

Complete parts list with manufacturer part numbers and substitutions.

Semiconductors: Transistors, ICs, diodes with original part numbers
Passive Components: Resistors, capacitors, inductors with values
Electromechanical: Relays, switches, connectors
Mechanical Parts: Screws, brackets, knobs, faceplate
Recommended Substitutions: Equivalent components when original unavailable

Tip: Always use genuine Marantz parts for optimal performance.

Alignment Procedures

Factory alignment procedures for optimal performance.

DC Offset Adjustment: VR101-VR105 for each channel
Bias Current Adjustment: VR201-VR205 for amplifier bias
FM Tuner Alignment: L001, L002 for FM front end
AM Tuner Alignment: T001 for AM oscillator
Display Brightness: VR301 for front panel display

WARNING! Use proper test equipment and follow procedures exactly.

Safety Precautions

Essential safety procedures for service technicians.

Always disconnect AC power before servicing. Discharge large capacitors. Use isolation transformer when testing live circuits. Follow ESD precautions. Use proper tools and test equipment.

CAUTION! Lethal voltages present. Only qualified personnel should perform service.

Schematics

Complete circuit schematics for all major sections.

Main System Schematic: Complete system overview
Power Supply Schematic: Detailed power circuit diagram
Amplifier Schematic: 5-channel amplifier circuits
Audio Processing Schematic: DSP and analog processing
Video Switching Schematic: Video input/output circuits
Control System Schematic: Microprocessor and interface
Tuner Schematic: AM/FM tuner circuits

Service Notes

Important service notes and common repair issues.

Common Failures: Power supply capacitors (C101-C104), output transistors (Q101-Q110), relay contacts. Special Tools: IC extractors, surface mount soldering equipment. Calibration Requirements: Audio analyzer for proper alignment.

Reset Procedure: Disconnect power, press and hold TUNER PRESET + and - while reconnecting power.

Service Support: Contact Marantz technical support for additional assistance.