Marantz MM8003 Service Manual

The Marantz MM8003 is a high-performance 8-channel power amplifier designed for professional and home theater applications. This service manual provides detailed technical information, specifications, schematics, and troubleshooting procedures for qualified service technicians. The amplifier features 140 watts per channel (8 ohms, 20Hz-20kHz, 0.05% THD), advanced thermal management, protection circuits, and balanced XLR inputs.

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

Technical Specifications

Complete technical specifications and performance characteristics of the Marantz MM8003 power amplifier.

Parameter	Specification
Power Output	140W x 8 (8Ω, 20Hz-20kHz, 0.05% THD)
Frequency Response	10Hz - 100kHz (+0/-3dB)
Total Harmonic Distortion	<0.05% (20Hz-20kHz at rated power)
Signal-to-Noise Ratio	110dB (A-weighted)
Input Sensitivity	1.2V (RCA), 2.4V (XLR)
Input Impedance	22kΩ (RCA), 20kΩ (XLR)
Damping Factor	>200 (8Ω, 20Hz-20kHz)
Power Consumption	1200W (max), 65W (standby)
Dimensions	440mm x 195mm x 463mm (WxHxD)
Weight	28.5 kg

Block Diagrams

System block diagrams showing signal flow and power distribution.

Main System Block Diagram: Overview of all functional blocks
Power Supply Block Diagram: AC input to DC distribution
Amplifier Channel Block Diagram: Input to output signal path
Protection Circuit Block Diagram: Overcurrent, thermal, DC protection
Control System Block Diagram: Microprocessor and interface circuits

WARNING! High voltages present - discharge capacitors before servicing.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Input Stage: Balanced XLR and unbalanced RCA input circuits
Voltage Amplification Stage: High-speed voltage amplification
Output Stage: Complementary MOSFET output transistors
Power Supply: Toroidal transformer and regulated supplies
Protection Circuits: DC detection, overcurrent, thermal protection
Control Circuit: Microprocessor and status indicators

CAUTION! Use proper grounding techniques when testing circuits.

Disassembly Procedures

Top Cover Removal: Remove 8 screws from rear panel
Front Panel Removal: Remove 4 screws from sides
Main Board Access: Remove shield and connector blocks
Power Supply Removal: Disconnect all wiring harnesses
Heat Sink Assembly: Remove thermal compound carefully
Output Module Replacement: Follow static precautions

Adjustment Procedures

Factory adjustment procedures requiring calibrated test equipment.

Required Equipment: Audio analyzer, oscilloscope, distortion analyzer, dummy loads, true RMS voltmeter.

DC Offset Adjustment: Adjust VR501-VR508 for <10mV DC output. Bias Current Adjustment: Set idle current to 50mA per channel. Gain Matching: Adjust input attenuators for channel balance. Protection Threshold: Verify protection circuit operation.

Parts List

Complete list of components with manufacturer part numbers.

Reference	Description	Part Number
Q701-Q708	Output MOSFET 2SK1530	2SK1530-Y
Q709-Q716	Output MOSFET 2SJ201	2SJ201-Y
IC501-IC508	Op-amp NJM2068	NJM2068DD
T001	Toroidal Transformer	TP-850M
C801-C808	Main Filter Capacitor	15,000μF/80V
F001	Main Fuse	T8A/250V

Schematics

Complete circuit schematics for all amplifier sections.

Main Amplifier Schematic: Complete channel circuit
Power Supply Schematic: Primary and secondary circuits
Protection Circuit Schematic: All protection functions
Control Board Schematic: Microprocessor and indicators
Input Board Schematic: XLR and RCA input circuits

Tip: Use original schematics for accurate component values.

PCB Layouts

Printed circuit board layouts and component placement diagrams.

Main Amplifier Board: Top and bottom layer views
Power Supply Board: Component placement and routing
Input Board: Balanced input circuit layout
Control Board: Microprocessor and interface layout
Overall Assembly: Board locations and interconnections

WARNING! Observe proper ESD precautions when handling PCBs.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Fuse blown, power supply fault	Check F001, measure primary voltage
Channel dead	Output devices, protection circuit	Check output MOSFETs, protection IC
Distortion	Bias current, damaged components	Adjust bias, check driver transistors
Protection mode	DC offset, overcurrent	Measure DC output, check current sense
Hum/buzz	Ground loop, filter capacitors	Check grounding, replace filter caps

Reset: Power cycle to clear protection lockout.

Safety Precautions

Critical safety information for service personnel.

High Voltage Warning: Dangerous voltages present even when unplugged. Component Handling: Use anti-static precautions for semiconductors. Test Equipment: Use isolation transformers when measuring primary side. Replacement Parts: Use only manufacturer-specified components.

CAUTION! Always discharge power supply capacitors before servicing.

Service Notes

Important service information and common repair procedures.

Factory Service Bulletins: Updated procedures and modifications. Common Failures: Output MOSFET replacement guidelines. Thermal Management: Heat sink assembly and thermal compound application. Calibration: Required test equipment and setup procedures. Warranty: Service documentation requirements and procedures.

Service Support: Contact Marantz technical support for additional assistance.