Marantz SR 220 Service Manual

The Marantz SR 220 is a high-performance stereo receiver featuring AM/FM tuner, multiple audio inputs, phono input, tape monitor, loudness control, and speaker outputs. This service manual provides detailed technical information for service technicians, including schematics, alignment procedures, troubleshooting guides, and replacement parts list for proper maintenance and repair of the SR 220 receiver.

Technical Specifications

Complete technical specifications for the Marantz SR 220 stereo receiver.

Parameter	Specification
Power Output	20 watts per channel, 8 ohms, 20Hz-20kHz
Total Harmonic Distortion	0.08% at rated output
Frequency Response	10Hz-50kHz (+0, -3dB)
Input Sensitivity	Phono: 2.5mV; Aux: 150mV
Signal-to-Noise Ratio	Phono: 70dB; Aux: 85dB
Tuner Section	AM/FM stereo with muting
Dimensions	17" W × 4.5" H × 12" D
Weight	15.4 lbs (7 kg)
Power Requirements	120V AC, 60Hz, 80W
Speaker Impedance	4-16 ohms

Block Diagram

System block diagram showing signal flow and major components.

1. Tuner Section: RF amplifier, mixer, local oscillator, IF stages
2. Preamplifier: Phono equalization, tone controls, volume
3. Power Amplifier: Driver stage, output transistors, protection circuit
4. Power Supply: Transformer, rectifier, filter capacitors, regulators
5. Control Section: Selector switches, mode controls, indicators

WARNING! High voltages present in power supply section. Exercise extreme caution when servicing.

Circuit Description

Detailed circuit analysis of major sections.

1. Power Supply: Dual secondary transformer providing ±25V for amplifier and lower voltages for preamp/tuner
2. Preamplifier: RIAA equalized phono stage, flat response aux inputs
3. Tone Controls: Bass and treble controls with center detent
4. Power Amplifier: Complementary symmetry output stage with current limiting
5. Protection Circuit: DC offset protection and thermal shutdown

CAUTION! Always discharge power supply capacitors before working on amplifier section.

Alignment Procedures

• FM Tuner Alignment: Requires FM signal generator, oscilloscope, and VTVM
• IF Alignment: 10.7MHz IF stages adjustment for proper bandwidth
• AM Tuner Alignment: 455kHz IF and oscillator tracking
• Stereo Decoder: 19kHz pilot carrier and 38kHz subcarrier adjustment
• Bias Adjustment: Power amplifier bias current setting
• DC Offset: Output DC offset voltage adjustment
• Required Test Equipment: Audio generator, oscilloscope, distortion analyzer, VTVM

Disassembly Instructions

Step-by-step disassembly procedure for service access.

Front Panel: Remove knobs, unscrew front panel assembly

Top Cover: Remove screws from rear and sides, lift cover straight up

Bottom Cover: Remove screws, carefully separate from chassis

Circuit Boards: Note cable positions before disconnecting, label all connections

1. Disconnect AC power cord
2. Remove all external connections
3. Remove knobs and front panel screws
4. Remove top cover screws
5. Lift top cover straight up
6. Document wire positions before disassembly

Troubleshooting Guide

Systematic troubleshooting approach for common problems.

Symptom	Possible Cause	Corrective Action
No sound from either channel	Power supply failure	Check fuse, power transformer, rectifiers
Distorted audio	Output transistors, bias circuit	Check output devices, adjust bias current
One channel dead	Amplifier section failure	Check signal path, transistors, capacitors
No FM reception	Tuner section failure	Check RF amplifier, local oscillator
Hum in audio	Ground loop, filter capacitors	Check ground connections, power supply filters

Parts List

Complete list of replacement parts with manufacturer part numbers.

1. Transistors: 2SC458 (Q101-Q104), 2SA493 (Q105, Q106)
2. Output Transistors: 2SC1061 (Q107, Q109), 2SA671 (Q108, Q110)
3. Diodes: 1S1555 (D101-D104), 1S2473 (D105, D106)
4. Electrolytic Capacitors: Various values and voltages
5. Integrated Circuits: TA7120P (IC101), μPC574J (IC102)
6. Transformers: Power (T901), output (T701, T702)

Tip: Use exact replacement parts for optimal performance and safety.

Schematic Diagrams

Complete schematic diagrams for all circuit sections.

1. Main Amplifier Schematic: Shows complete audio power amplifier circuit
2. Preamplifier Schematic: Phono and line level input circuits
3. Power Supply Schematic: Transformer, rectification, and regulation
4. Tuner Schematic: AM/FM tuner and stereo decoder circuits
5. Control Schematic: Selector switches, tone controls, indicators

WARNING! Schematics show lethal voltages. Service by qualified technicians only.

PCB Layouts

Printed circuit board layouts and component placement diagrams.

Main Amplifier Board: Component side and solder side views

Preamplifier Board: Component locations and trace routing

Tuner Board: RF and IF section component placement

Power Supply Board: Transformer and filter capacitor locations

Service Precautions

Important safety precautions for service technicians.

Always use isolation transformer when servicing AC/DC circuits. Discharge large capacitors before testing. Use appropriate fuses - never bypass. Ensure proper grounding of test equipment.

CAUTION! Lethal voltages present. Service by qualified personnel only.

Test Equipment Requirements

Recommended test equipment for proper service and alignment.

Equipment	Specifications	Purpose
Audio Generator	20Hz-20kHz, low distortion	Amplifier testing
Oscilloscope	Dual trace, 20MHz minimum	Waveform observation
Distortion Analyzer	0.01% minimum resolution	THD measurements
VTVM/VOM	High impedance input	Voltage measurements
RF Signal Generator	AM/FM modulation	Tuner alignment

Reset: No user-accessible reset function. Service reset requires component replacement.

Service Support: Contact authorized Marantz service centers for genuine parts and technical support.