Marantz PM7004 Service Manual

The Marantz PM7004 is a high-performance integrated stereo amplifier featuring advanced HDAM (Hyper Dynamic Amplifier Module) technology, high-current power supply, toroidal transformer, and multiple input/output options. This service manual covers technical specifications, circuit diagrams, adjustment procedures, troubleshooting, and maintenance guidelines for qualified service technicians.

1. Technical Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Adjustment Procedures 5. Disassembly Instructions 6. PCB Layouts 7. Parts List 8. Troubleshooting Guide 9. Safety Precautions 10. Test Points & Measurements

Technical Specifications

Detailed technical specifications and performance characteristics of the PM7004 amplifier.

Parameter	Specification
Power Output	85W + 85W (8Ω, 20Hz-20kHz, 0.08% THD)
Frequency Response	10Hz-100kHz (+1/-3dB)
Total Harmonic Distortion	0.02% (20Hz-20kHz, 50W, 8Ω)
Input Sensitivity	200mV (MM), 2.5mV (MC)
Signal-to-Noise Ratio	100dB (Line), 74dB (MM)
Damping Factor	100 (8Ω, 1kHz)
Power Consumption	230W (max), 65W (no signal)
Dimensions	440 x 385 x 125mm (W x D x H)
Weight	10.5kg
Power Supply	AC 120V/230V, 50/60Hz

Block Diagrams

System block diagrams showing signal flow and power distribution.

Main System Block Diagram: Overview of entire amplifier system
Power Amplifier Block: HDAM-SA2 circuit configuration
Power Supply Block: Toroidal transformer and regulation circuits
Pre-amplifier Block: Input selection and tone control circuits
Protection Circuit Block: DC detection and thermal protection

WARNING! High voltages present - discharge capacitors before servicing.

Circuit Descriptions

Detailed circuit analysis and component functions.

Power Amplifier Stage: Complementary push-pull configuration with HDAM technology
Pre-amplifier Stage: Discrete component design with low noise transistors
Phono Equalizer: RIAA accurate equalization for MM/MC cartridges
Tone Control: Bass and treble controls with bypass capability
Protection Circuit: Speaker relay with DC offset and thermal protection

CAUTION! Use only specified replacement components.

Adjustment Procedures

DC Offset Adjustment: VR601/VR602 for left/right channels
Bias Current Adjustment: VR603/VR604 for optimal Class AB operation
Phono Stage Gain: R105/R205 for MM input sensitivity
Protection Threshold: Adjust DC detection level if required
Power Supply Voltages: Verify ±48V rails and regulated supplies
Test Equipment Required: Oscilloscope, DMM, audio generator, dummy loads
Test Conditions: 1kHz sine wave, 8Ω load, specified input levels

Disassembly Instructions

Step-by-step disassembly procedure for service access.

Procedure: Power off and unplug unit before disassembly.

Remove top cover: 8 screws on rear and sides
Remove bottom cover: 6 screws on bottom panel
Front panel removal: 4 screws behind volume knob
Main board access: Remove input/output connectors
Heat sink removal: Required for output transistor replacement

Tip: Document screw locations and cable routing during disassembly.

PCB Layouts

Printed circuit board layouts and component locations.

Main Amplifier Board: Component side and solder side views
Power Supply Board: Transformer connections and rectifier circuits
Input Selector Board: Source switching and phono stage
Front Panel Board: Display and control circuits
Protection Board: Relay driver and sensing circuits

WARNING! Observe electrostatic discharge precautions when handling PCBs.

Parts List

Complete component listing with manufacturer part numbers.

Component	Part Number	Description
Output Transistors	2SC5200/2SA1943	Complementary power transistors
Power Transformer	TP-450	Toroidal, 450VA
Main Capacitors	15,000μF/63V	Power supply filter
Relay	MY4-02-DC24	Speaker protection
Volume Control	RK27112	ALPS motorized potentiometer
Fuse	T5A/250V	Slow-blow mains fuse
HDAM Modules	HDAM-SA2	Discrete amplifier modules

Troubleshooting Guide

Common failure symptoms and diagnostic procedures.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check F801 fuse, power switch S801, transformer primary
Protection mode	DC offset, short circuit	Measure DC at speaker terminals, check output transistors
Distorted audio	Bias current, damaged transistors	Adjust bias current VR603/604, test output devices
Hum/buzz	Ground loops, capacitor failure	Check ground connections, test power supply capacitors
No phono input	Phono stage components	Test Q101-Q104, check RIAA equalization network

Reset: Check protection circuit operation and reset if necessary.

Safety Precautions

Essential safety procedures for service technicians.

Use isolation transformer when testing live circuits. Discharge large capacitors before servicing. Observe proper grounding techniques. Use appropriate personal protective equipment.

CAUTION! Lethal voltages present - qualified personnel only.

Test Points & Measurements

Designated test points and standard measurement procedures.

TP1/TP2: Left/right channel DC offset measurement
TP3/TP4: Bias current measurement points
TP5: +48V power supply test point
TP6: -48V power supply test point
TP7/TP8: Regulated ±15V supplies
Measurement Procedure: Follow specified test conditions and use calibrated equipment
Tolerance: All measurements within ±10% unless otherwise specified