Marantz 22 Service Manual

The Marantz 22 is a classic stereo receiver featuring 22 watts per channel RMS power output, FM/AM tuner with advanced tuning capabilities, high-quality phono inputs for turntables, multiple audio inputs, tone controls, loudness compensation, and robust construction. This service manual provides comprehensive technical information for service technicians, including schematics, alignment procedures, troubleshooting guides, and replacement parts information.

1. Technical Specifications 2. Block Diagram Overview 3. Circuit Descriptions 4. Alignment Procedures 5. Troubleshooting Guide 6. Parts List 7. Schematics 8. Mechanical Assembly 9. Safety Precautions 10. Service Notes

Technical Specifications

Complete electrical and mechanical specifications for the Marantz 22 stereo receiver.

Parameter	Specification
Power Output	22 watts per channel RMS (8 ohms, 20Hz-20kHz)
Total Harmonic Distortion	Less than 0.3% at rated output
Frequency Response	20Hz-20kHz ±1dB
Input Sensitivity	Phono: 2.5mV; Aux: 250mV
Signal-to-Noise Ratio	Phono: 70dB; Aux: 85dB
Tuner Section	FM/AM with multiplex stereo
Power Requirements	120V AC, 60Hz, 150 watts
Dimensions	17" W × 5" H × 13" D
Weight	22 lbs

Block Diagram Overview

Functional block diagram showing signal flow and major circuit sections.

Power Supply: Transformer, rectifiers, and regulators
Tuner Section: FM/AM RF and IF stages
Preamplifier: Phono equalization and line stages
Power Amplifier: Driver and output stages
Control Section: Volume, balance, tone controls
Protection Circuit: Speaker protection and thermal management

WARNING! High voltages present in power supply and amplifier sections. Use proper safety precautions.

Circuit Descriptions

Detailed analysis of major circuit sections and their operation.

Power Supply: Dual secondary transformer with bridge rectification
FM Tuner: RF amplifier, mixer, IF stages, and multiplex decoder
Phono Preamplifier: RIAA equalization with low-noise transistors
Power Amplifier: Complementary symmetry output configuration
Tone Control: Bass and treble controls with selectable turnover frequencies

NOTE: All voltage measurements referenced to chassis ground unless otherwise specified.

Alignment Procedures

Step-by-step alignment instructions for optimal performance.

FM IF Alignment: 10.7MHz IF strip adjustment procedure
FM Front End: RF and oscillator coil adjustments
AM Alignment: IF and RF alignment steps
Stereo Decoder: 19kHz and 38kHz alignment
DC Offset: Power amplifier DC balance adjustment
Bias Current: Output stage bias adjustment procedure

Troubleshooting Guide

Systematic troubleshooting approach for common problems.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check main fuse; verify AC power; test transformer
One channel dead	Output transistors, driver stage	Check output transistors; test driver stage voltages
Distorted audio	Bias current, leaky capacitors	Adjust bias; replace electrolytic capacitors
No FM reception	Tuner section, multiplex decoder	Check tuner voltages; align IF stages
Hum in audio	Ground loops, filter capacitors	Check ground connections; test power supply capacitors

Service Tip: Always start troubleshooting with power supply measurements.

Parts List

Complete listing of components with manufacturer part numbers.

Component	Part Number	Description
Output Transistors	2SC1116/2SA747	Complementary power transistors
Power Transformer	TP-701	Dual secondary 35V-0-35V
Main Filter Caps	6800μF/50V	Power supply filter capacitors
FM Tuner IC	HA1156	FM IF and detector
Stereo Decoder	HA1156W	Multiplex stereo decoder

Schematics

Complete schematic diagrams for all circuit sections.

Main Amplifier Schematic: Power amplifier and driver stages
Power Supply Schematic: Transformer, rectification, and regulation
Preamplifier Schematic: Phono and line level inputs
FM Tuner Schematic: RF, IF, and detector circuits
Control Section: Switches, potentiometers, and indicators

NOTE: Schematics show component values and test points.

Mechanical Assembly

Disassembly and reassembly instructions with exploded views.

Step-by-step chassis removal, board access, and component replacement procedures. Includes torque specifications for mechanical fasteners and proper heat sink mounting techniques.

CAUTION! Handle PC boards carefully to avoid damage to traces and components.

Safety Precautions

Essential safety information for service personnel.

Always disconnect AC power before servicing
Use isolation transformer when working on live circuits
Discharge large capacitors before handling
Use proper grounding techniques
Wear safety glasses when soldering or cutting

WARNING! Lethal voltages present even when unit is switched off.

Service Notes

Important service tips and common repair issues.

Common failure points include output transistors, power supply capacitors, and selector switches. Always verify replacement transistor specifications match originals. Use thermal compound when replacing output devices. Document all modifications and component substitutions.

For technical support contact Marantz Service Department or authorized service centers.