Marantz PMD 350 Service Manual

The Marantz PMD 350 is a professional portable digital recorder featuring compact flash storage, XLR inputs with phantom power, built-in stereo microphones, USB connectivity, variable speed playback, and professional audio quality. Designed for field recording, journalism, and broadcast applications. Below are key sections for technical specifications, maintenance procedures, troubleshooting, and service information.

1. Technical Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Disassembly Procedures 5. Alignment & Calibration 6. Power Supply Section 7. Audio Circuitry 8. Display & Controls 9. Maintenance Schedule 10. Parts List 11. Troubleshooting Guide

Technical Specifications

Key technical parameters and performance characteristics of the PMD 350 recorder.

Parameter	Specification
Recording Format	Linear PCM, MP3
Sample Rates	44.1kHz, 48kHz, 96kHz
Bit Depth	16-bit, 24-bit
Storage Media	CompactFlash Card
Inputs	2 XLR/TRS combo, 3.5mm stereo
Outputs	XLR, 3.5mm headphone
Phantom Power	+48V
Power Supply	6V DC, 4 AA batteries
Frequency Response	20Hz - 20kHz ±1dB
Signal-to-Noise	>90dB

Block Diagrams

System architecture and signal flow diagrams.

Main System Block Diagram: Shows overall signal path from input to storage.
Power Supply Block Diagram: Illustrates power distribution throughout the unit.
Audio Processing Block Diagram: Details ADC/DAC and DSP signal flow.
Control System Diagram: Microprocessor and user interface architecture.

WARNING! Service should only be performed by qualified technicians. High voltages present in power supply section.

Circuit Descriptions

Detailed explanations of major circuit sections.

Analog Input Stage: Balanced XLR inputs with phantom power circuitry.
A/D Conversion: 24-bit sigma-delta converter operation.
Digital Signal Processing: FPGA-based audio processing.
Power Regulation: Switching and linear regulator circuits.
Clock Generation: Master clock and sample rate generation.

CAUTION! Static-sensitive components; use proper ESD protection.

Disassembly Procedures

Case Removal: Remove 8 screws from bottom case.
Main Board Access: Disconnect ribbon cables and remove mounting screws.
Display Module: Carefully detach LCD flex cable.
Front Panel: Remove knob caps and control board.
Power Supply Board: Disconnect battery and DC input connectors.
Reassembly: Reverse procedure, ensuring all connectors are secure.

Alignment & Calibration

Service adjustments and calibration procedures.

Test Equipment Required: Audio analyzer, oscilloscope, digital multimeter, test CDs.

Input Gain Calibration: Adjust trimpots R101, R102 for +4dBu reference.
Output Level Calibration: Set output for 0dBFS reference.
Clock Alignment: Verify sample clock accuracy with frequency counter.
Battery Calibration: Calibrate battery meter for accurate remaining time display.

Power Supply Section

Power system detailed service information.

Main Components: DC input jack, battery contacts, power switch, regulator ICs.

External Power: 6V DC input through protection diode D101.
Battery Power: 4 AA cells in series, monitored by microprocessor.
Voltage Regulation: +3.3V and +5V rails for digital/analog circuits.
Power Management: Auto-shutdown and low-battery warning circuits.

Tip: Check fuse F101 first when troubleshooting power issues.

Audio Circuitry

Detailed audio path service information.

Microphone Preamps: IC201, IC202 with gain switching.
Line Inputs: Balanced receiver circuits with impedance matching.
Headphone Amplifier: IC301 capable of driving 32-600 ohm loads.
Monitor Circuit: Separate output for confidence monitoring.
Metering: LED and LCD level display drivers.

WARNING! Phantom power voltages can damage test equipment; use blocking capacitors.

Display & Controls

User interface service procedures.

LCD Display: 2-line backlit display, controlled via serial interface.
Rotary Encoders: Digital encoders for level controls.
Pushbuttons: Matrix-scanned with debounce circuitry.
LED Indicators: Record, battery, error status indicators.

Maintenance Schedule

Recommended preventive maintenance procedures.

Interval	Procedure
6 months	Clean heads and tape path
1 year	Calibration check
2 years	Battery contact cleaning
As needed	Button/control cleaning

CAUTION! Use only approved cleaning solutions; avoid abrasives.

Parts List

Service replacement parts and components.

Main PCB Assembly: Part # PMD350-MAIN-01
Front Panel Assembly: Part # PMD350-FRONT-01
LCD Display: Part # LCD-2402-BL
Power Supply IC: IC101 - REG-5V-1A
Audio Codec: IC401 - AKM5394A
Case Set: Part # PMD350-CASE-01

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Battery/DC input	Check batteries, DC jack, fuse F101
No audio recording	Input selection/mutes	Verify input source, check mute circuits
Distorted audio	Overload/clipping	Reduce input level, check preamp stages
Card not recognized	Format/compatibility	Reformat card, verify FAT32 format
Display issues	Connections/backlight	Check ribbon cable, backlight inverter

Factory Reset: Hold STOP + PLAY while powering on.

Service Support: Contact authorized Marantz service centers for technical assistance.