marantz pm 57 service manual

The Marantz PM 57 is a high-quality stereo integrated amplifier featuring advanced audio circuitry, multiple input/output options, and robust construction. This service manual provides comprehensive technical information for qualified service technicians, including schematics, alignment procedures, component specifications, and troubleshooting guidelines for proper maintenance and repair of the amplifier unit.

1. Technical Specifications 2. Block Diagram Overview 3. Circuit Description 4. Disassembly Instructions 5. Alignment Procedures 6. Component Layout 7. Schematic Diagrams 8. Parts List 9. Test Points & Measurements 10. Troubleshooting Guide 11. Safety Precautions

Technical Specifications

Detailed electrical and mechanical specifications for the Marantz PM 57 integrated amplifier.

Parameter	Specification
Power Output	2 x 60W RMS (8Ω, 20Hz-20kHz)
Total Harmonic Distortion	<0.05% (rated power)
Frequency Response	10Hz - 50kHz (+0/-3dB)
Input Sensitivity	Phono: 2.5mV; Line: 150mV
Signal-to-Noise Ratio	Phono: 80dB; Line: 100dB
Input Impedance	Phono: 47kΩ; Line: 50kΩ
Damping Factor	>100 (8Ω, 1kHz)
Power Consumption	220W maximum
Dimensions (WxHxD)	440 x 115 x 345 mm
Weight	7.5 kg

Block Diagram Overview

System block diagram showing signal flow and major functional blocks.

Input Selector Circuit: CD, Tuner, Phono, Aux, Tape inputs
Phono Equalization Stage: RIAA equalization circuit
Tone Control Circuit: Bass and treble adjustment
Volume/Balance Control: ALPS potentiometer assembly
Power Amplifier Stage: Complementary symmetry output
Protection Circuit: DC detection and thermal protection
Power Supply Unit: Toroidal transformer and regulation

WARNING! High voltage present in power supply section. Disconnect from mains before servicing.

Circuit Description

Detailed explanation of major circuit sections and their operation.

Input Stage: JFET and bipolar transistor input circuitry
Phono Preamp: Discrete component RIAA equalization
Tone Control: Baxandall-type bass and treble controls
Power Amplifier: Complementary Darlington output stage
Protection Circuit: Relay-based speaker protection
Power Supply: Dual rail ±35V DC supply

CAUTION! Use proper grounding techniques when testing live circuits.

Disassembly Instructions

Case Removal: Remove 6 screws from top panel and 4 from bottom.
Front Panel: Remove knobs and 4 mounting screws.
Main Board: Desolder connections and remove 8 mounting points.
Power Supply: Discharge capacitors before handling.
Heat Sink: Remove thermal compound carefully during reassembly.
Input Selector: Note switch positions before disassembly.
Volume Control: Mark shaft positions for proper reassembly.

Alignment Procedures

Required test equipment: Audio oscillator, oscilloscope, distortion analyzer, multimeter.

DC Offset Adjustment: Adjust VR501/VR502 for 0V ±10mV at speaker terminals.

Bias Current: Set VR503/VR504 for 15mA across emitter resistors.

Phono Equalization: Verify RIAA curve accuracy using test records.

Input Sensitivity: Calibrate using 1kHz test signal at specified levels.

Component Layout

PCB component identification and physical locations.

Board	Major Components	Location Reference
Main Board	Input transistors, tone control ICs	CN1-CN8 connectors
Power Amp Board	Output transistors, bias circuitry	Q701-Q708, R701-R712
Power Supply	Transformer, rectifiers, capacitors	T801, D801-D804, C801-C804
Front Panel	Switches, potentiometers, indicators	S101-S105, VR101-VR103
Rear Panel	Input/output connectors, fuse holder	J201-J208, F801

Schematic Diagrams

Complete circuit schematics for all amplifier sections.

Main Amplifier Circuit: Input to driver stage
Power Output Stage: Complementary output configuration
Power Supply: Transformer, rectification, and filtering
Phono Preamp: RIAA equalization network
Tone Control: Bass and treble frequency shaping
Protection Circuit: DC detection and relay control
Input Selector: Source switching matrix

Tip: Refer to component layout when tracing circuits on PCB.

Parts List

Complete component listing with manufacturer part numbers.

Reference	Description	Part Number	Value/Rating
Q701-Q704	Output Transistor	2SC3281/2SA1302	200V, 15A
C801,C802	Main Filter Capacitor	EKMQ631VSN103MA40S	10,000μF/63V
IC501,IC502	Op-amp	NJM4558	Dual op-amp
D801-D804	Rectifier Diode	1N5404	3A, 400V
R701-R704	Emitter Resistor	MRS250.47R F	0.47Ω, 5W
F801	Main Fuse	5A, 250V	Time delay type

Test Points & Measurements

Critical test points and expected voltage measurements.

TP1, TP2: Power supply rails - ±35V DC
TP3, TP4: Amplifier output - 0V DC offset
TP5: Bias voltage - 0.5V across emitter resistors
TP6: Protection circuit trigger - 2.5V threshold
TP7, TP8: Phono stage output - check for oscillation

WARNING! Use isolated test equipment when measuring high voltage points.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No sound output	Protection relay, blown fuse	Check speaker terminals for DC; replace fuse F801
Distorted audio	Bias current, output transistors	Adjust bias current; test output transistors
Hum in output	Ground loop, filter capacitors	Check ground connections; replace C801,C802
One channel dead	Input selector, amplifier stage	Test signal path; check Q701-Q704
Overheating	Bias current, ventilation	Adjust bias; ensure proper heat sink contact

Reset: Check all adjustments after component replacement.

Service: Authorized Marantz service centers only for warranty work.