Marantz MA9S2 Service Manual

The Marantz MA9S2 is a high-end monoblock power amplifier featuring advanced HDAM (Hyper Dynamic Amplifier Module) technology, fully balanced circuitry, massive toroidal transformer, high-current power supply, dual mono construction, and premium audiophile-grade components. Below are key sections for technical specifications, circuit description, service procedures, alignment instructions, troubleshooting, and parts list.

1. Technical Specifications 2. Circuit Description 3. Block Diagram 4. Service Procedures 5. Test Points & Measurements 6. Alignment Instructions 7. Troubleshooting Guide 8. Parts List 9. Schematics 10. Safety Precautions 11. Warranty Information

Technical Specifications

Key performance parameters and electrical characteristics of the MA9S2 monoblock amplifier.

Parameter	Specification
Power Output	200W RMS into 8Ω, 400W RMS into 4Ω
Frequency Response	5Hz - 100kHz (+0/-3dB)
Total Harmonic Distortion	<0.005% (20Hz-20kHz at rated power)
Signal-to-Noise Ratio	>110dB (A-weighted)
Input Sensitivity	1.2V for rated output
Input Impedance	47kΩ balanced, 22kΩ unbalanced
Damping Factor	>500 (8Ω, 20Hz-20kHz)
Power Consumption	650W maximum, 85W standby
Dimensions	440mm W × 195mm H × 465mm D
Weight	32kg per monoblock

Circuit Description

Detailed explanation of the MA9S2 amplifier circuitry and design philosophy.

Input Stage: Fully balanced differential amplifier using HDAM-SA2 modules
Voltage Amplification: High-speed current feedback topology
Output Stage: Triple-parallel push-pull configuration with 6 power transistors per channel
Power Supply: Dual-mono design with 1.2kVA toroidal transformer and 80,000μF filtering
Protection Circuitry: DC detection, over-current, over-temperature, and soft-start systems

WARNING! High voltages present - qualified service personnel only. Disconnect power before servicing.

Block Diagram

System overview showing signal flow and major functional blocks.

Input Section: XLR balanced input, RCA unbalanced input, input selector relay
Amplification: HDAM input buffer, voltage gain stage, driver stage, output stage
Power Supply: Main transformer, rectifier bridges, filter capacitors, regulation circuits
Protection: Microprocessor control, temperature sensors, current monitoring
Output: Speaker relay, output inductors, protection circuitry

Service Procedures

Step-by-step instructions for common service operations.

Case Removal: Remove 12 screws from rear and sides, lift top cover carefully
Board Access: Disconnect internal wiring harnesses before board removal
Component Replacement: Desolder carefully to avoid pad damage
Bias Adjustment: Monitor test points TP1-TP4 while adjusting VR101-VR104
DC Offset Calibration: Adjust VR105-VR106 for <10mV output offset

CAUTION! Large capacitors retain charge - discharge before servicing.

Test Points & Measurements

Critical test points and expected voltage measurements.

Test Point	Description	Normal Voltage
TP1	Positive rail voltage	+75V DC ±5%
TP2	Negative rail voltage	-75V DC ±5%
TP3	Output stage bias	25mV ±5mV
TP4	DC offset	<10mV
TP5	+15V regulator output	+15V DC ±0.5V
TP6	-15V regulator output	-15V DC ±0.5V

Alignment Instructions

Factory adjustment procedures for optimal performance.

Bias Current: Connect millivoltmeter to TP3, adjust VR101 for 25mV
DC Offset: Connect voltmeter to speaker terminals, adjust VR105 for 0V ±10mV
Symmetry: Check both channels match within 5%
Temperature: Allow 30 minutes warm-up before final adjustments

Note: Use specified test equipment and follow exact procedure sequence.

Troubleshooting Guide

Common problems and diagnostic procedures.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check F101-F102, power switch, primary winding
Protection mode	DC offset, over-current	Measure output DC, check output transistors
Distortion	Bias current, damaged transistors	Adjust bias, check Q101-Q106, Q201-Q206
Hum/buzz	Grounding, filter capacitors	Check ground connections, measure ripple
Intermittent operation	Cold solder, connectors	Inspect solder joints, clean connectors

Parts List

Critical replacement components and part numbers.

Power Transistors: 2SC5200 (Q101-Q103), 2SA1943 (Q201-Q203)
Driver Transistors: 2SC2705 (Q104-Q105), 2SA1145 (Q204-Q205)
HDAM Modules: HDAM-SA2 (IC101, IC201)
Main Fuses: F101, F102 - T8A/250V
Filter Capacitors: C101-C104 - 20,000μF/80V
Rectifier Diodes: D101-D108 - 15A/200V

Schematics

Reference to detailed circuit diagrams included in full manual.

Main Amplifier Circuit - Pages 12-15
Power Supply - Pages 16-18
Protection Circuit - Pages 19-20
Input Selector - Page 21
PCB Layout - Pages 22-25

Note: Schematics show component values, test points, and interconnection details.

Safety Precautions

Essential safety information for service technicians.

Always disconnect AC power before servicing. Discharge main capacitors through 100Ω/10W resistor. Use isolation transformer when testing live circuits. Wear safety glasses. Follow ESD precautions with semiconductors.

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

Warranty Information

Manufacturer warranty terms and service support.

Marantz MA9S2 carries 3-year limited warranty. Warranty void if serviced by unauthorized personnel. For service support, contact authorized Marantz service centers. Keep original packaging for safe transport. Serial number required for warranty claims.

Support: Marantz Service Department - 1-800-654-6633 • www.marantz.com