Marantz PM-40 SE Service Manual

The Marantz PM-40 SE is a high-quality stereo integrated amplifier featuring advanced audio circuitry, dual mono construction, gold-plated connectors, MM phono input, CD direct input, tone controls, loudness compensation, and speaker A/B switching. With 40 watts per channel into 8 ohms, this amplifier delivers exceptional sound quality for audiophile applications. Below are key sections for technical specifications, circuit diagrams, adjustment procedures, parts list, and service information.

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

Technical Specifications

Key performance characteristics and electrical parameters of the Marantz PM-40 SE amplifier.

Parameter	Specification
Power Output	40W + 40W (8Ω, 20Hz-20kHz, 0.08% THD)
Total Harmonic Distortion	0.08% (20Hz-20kHz at rated output)
Frequency Response	5Hz-50kHz (+0/-3dB)
Input Sensitivity	Phono: 2.5mV; CD: 150mV; Tuner: 150mV
Signal-to-Noise Ratio	Phono: 80dB; CD: 100dB
Input Impedance	Phono: 47kΩ; CD: 50kΩ
Tone Controls	Bass: ±10dB at 100Hz; Treble: ±10dB at 10kHz
Power Supply	AC 120V/230V, 50/60Hz
Dimensions	440 x 125 x 355mm (W x H x D)
Weight	7.5kg

Block Diagram

System overview showing signal flow and major functional blocks.

Input Selector: Phono, CD, Tuner, Aux, Tape
Phono Equalizer: RIAA correction for magnetic cartridges
Tone Control: Bass and treble adjustment circuits
Volume Control: ALPS motorized potentiometer
Power Amplifier: Dual mono construction with discrete output stages
Power Supply: Toroidal transformer with dual rectification
Protection Circuit: DC offset and thermal protection

NOTE: All signal paths are fully balanced for minimal noise and distortion.

Circuit Description

Detailed explanation of major circuit sections and their operation.

Phono Stage: Discrete FET input with passive RIAA equalization
Line Stage: JFET differential amplifier with current mirror loading
Tone Control: Baxandall-type active tone control circuit
Power Amplifier: Complementary symmetry output with triple Darlington configuration
Power Supply: Dual secondary toroidal transformer with separate rectification for each channel
Protection: Relay-based speaker protection with DC detection

CAUTION! High voltages present - discharge capacitors before servicing.

Adjustment Procedures

DC Offset: Adjust VR101/VR201 for 0mV ±5mV at speaker terminals
Bias Current: Set VR102/VR202 for 15mA across emitter resistors
Phono Balance: Adjust for equal output from both channels
Tone Control Center: Verify flat response at center detent positions
Protection Circuit: Test relay operation and timing
Power Supply: Verify ±35V DC rails under load

Parts List

Access OSD via TV MENU or SETUP (DVD). Front Panel: POWER, OPEN/CLOSE, AUTO/DPMS, MUTE.

Critical Components: Output transistors (2SC3281/2SA1302), Power transformer (TP-240), Main filter capacitors (10,000μF/50V), Volume control (RK-40), Input selector (ALPS), Protection relay (MY4-02).

Semiconductors: Q101-Q104 (2SK170), Q105-Q108 (2SA970), Q109-Q112 (2SC2240), Q113-Q116 (2SA1302/2SC3281). Resistors: Metal film 1/4W ±1%, Power resistors 5W. Capacitors: Audio grade electrolytic and film types.

PCB Layouts

Main amplifier board: Double-sided FR-4 with ground plane. Power supply board: Single-sided with heavy copper traces.

Identify component locations using silkscreen markings
Follow signal flow from input to output stages
Note grounding scheme: Star ground at power supply
Observe high-current paths for output stages

Tip: Use original Marantz parts for critical audio path components.

Schematic Diagrams

Complete schematics for all circuit sections.

Main Amplifier: Left and right channel power amplifier circuits
Pre-amplifier: Phono and line stage with tone controls
Power Supply: Transformer, rectification, and filtering
Protection Circuit: DC detection and relay driver
Control Section: Input selector and volume control
Front Panel: Switches, indicators, and connectors

WARNING! Schematics show lethal voltages - exercise extreme caution.

Service Notes

Common service issues and recommended procedures. Thermal management: Ensure proper heatsink contact for output transistors. Capacitor replacement: Use low-ESR types for power supply. Transistor matching: Replace output pairs with matched devices.

Safety Precautions

Always disconnect from AC power before servicing. Use isolation transformer when testing live circuits. Discharge large capacitors before handling. Follow ESD precautions for semiconductor devices.

CAUTION! Lethal voltages present - qualified technicians only.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check main fuse F001; verify transformer primary; test power switch.
One channel dead	Output transistors, protection circuit	Test output devices Q113-Q116; check protection relay; measure DC offset.
Distortion	Bias current, damaged transistors	Adjust bias current; replace matched output pairs; check driver transistors.
Hum/buzz	Grounding, filter capacitors	Verify ground connections; replace main filter capacitors; check input shielding.
No phono signal	Phono stage, selector switch	Test phono transistors Q101-Q104; clean selector switch; verify RIAA network.

Service Contact: Authorized Marantz service centers only.

Technical Support: Refer to Marantz service department for schematic updates.