Marantz PMD321 Service Manual

The Marantz PMD321 is a professional portable digital recorder featuring high-quality audio recording capabilities, built-in stereo microphones, USB connectivity, SD card storage, multiple recording formats, and professional audio inputs/outputs. This service manual provides comprehensive technical information for service technicians, including schematics, disassembly procedures, troubleshooting, and maintenance guidelines.

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

Technical Specifications

Detailed technical specifications for the Marantz PMD321 professional recorder.

Parameter	Specification
Recording Format	WAV (16/24-bit), MP3
Sample Rates	44.1kHz, 48kHz, 96kHz
Storage Media	SD/SDHC card (up to 32GB)
Inputs	XLR combo jacks, 3.5mm stereo mini jack
Outputs	3.5mm stereo headphone, USB 2.0
Microphones	Built-in stereo condenser mics
Power Supply	2x AA batteries or USB power
Battery Life	Approx. 4 hours (alkaline batteries)
Dimensions	128 x 65 x 28 mm
Weight	180g (without batteries)

Block Diagrams

System block diagrams showing signal flow and component relationships.

Main System Block Diagram: Shows overall signal path from input to output.
Audio Processing Block Diagram: Details ADC/DAC and DSP signal flow.
Power Supply Block Diagram: Illustrates power distribution and regulation.
Control System Block Diagram: Microprocessor and interface control paths.

NOTE: Refer to schematics for detailed component-level information.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Analog Input Stage: Balanced XLR inputs with phantom power capability.
Preamplifier Circuit: Low-noise mic preamps with gain control.
ADC Section: 24-bit analog-to-digital conversion circuitry.
Digital Signal Processor: Main audio processing and format conversion.
Power Management: Battery monitoring and power regulation.
USB Interface: USB 2.0 data transfer and charging circuit.

Disassembly Procedures

Step-by-step instructions for disassembling the PMD321 unit.

Remove battery cover and batteries.
Remove six Phillips screws from bottom case.
Carefully separate top and bottom case halves.
Disconnect internal ribbon cables and flex circuits.
Remove main PCB assembly from case.
Access individual components as needed.

WARNING! Use proper ESD protection. Handle flex cables with care to avoid damage.

Alignment & Calibration

Calibration procedures and alignment specifications.

Procedure	Test Equipment Required	Specification
Input Level Calibration	Audio analyzer, test generator	±0.5dB channel balance
Frequency Response	Sweep generator, analyzer	20Hz-20kHz ±1dB
THD+N Measurement	Distortion analyzer	<0.01% @ 1kHz
Battery Voltage Calibration	Digital multimeter	Accurate to ±0.1V

Troubleshooting Guide

Common issues and diagnostic procedures.

Symptom	Possible Cause	Corrective Action
No power	Dead batteries, faulty power circuit	Check battery voltage, test DC-DC converter
No audio recording	Input circuit failure, mic problem	Test input stages, check mic bias voltage
SD card not recognized	Card reader failure, format issue	Clean card contacts, test with known good card
USB connection issues	USB IC failure, connector damage	Check USB IC voltages, inspect connector
Distorted audio	Overload, ADC failure	Check input levels, test ADC reference

Parts List

Complete list of components with part numbers and descriptions.

Main ICs: DSP processor, ADC, DAC, USB controller
Passive Components: Resistors, capacitors, inductors
Connectors: XLR jacks, USB port, headphone jack
Mechanical Parts: Case screws, buttons, battery contacts
PCB Assemblies: Main board, display board, input board

PCB Layouts

Printed circuit board layouts and component placement diagrams.

Main PCB - Top Layer: Component placement and routing.
Main PCB - Bottom Layer: SMD components and ground plane.
Input Board: XLR connectors and preamp circuitry.
Display Board: LCD and control button connections.

NOTE: All dimensions in millimeters. Use for component replacement and trace repair.

Wiring Diagrams

Internal wiring and cable interconnection diagrams.

Detailed wiring for:

Power supply connections
Audio signal paths
Control and data buses
Display and button matrix
External connector wiring

Service Notes

Important service tips and special procedures.

Use only specified replacement parts
Follow ESD precautions during service
Record calibration data before adjustments
Verify firmware version before programming
Test all functions after repair completion

CAUTION! Improper service may void warranty and cause additional damage.

Safety Precautions

Essential safety information for service personnel.

Always disconnect power before servicing. Use insulated tools when working on powered circuits. Follow local electrical safety regulations. Replace safety-critical components only with specified parts. Ensure proper reassembly to maintain original safety standards.

WARNING! High voltages may be present in power supply circuits. Only qualified technicians should perform internal repairs.