Marantz 2252B Service Manuals

The Marantz 2252B is a classic stereo receiver from the 1970s featuring 52 watts per channel, high-quality audio components, and the iconic Marantz design. This service manual provides comprehensive technical documentation for repair, maintenance, and troubleshooting of the 2252B receiver. Below are key sections covering specifications, circuit diagrams, alignment procedures, parts lists, and service guidelines.

1. Technical Specifications 2. Block Diagrams 3. Circuit Schematics 4. Alignment Procedures 5. Parts List 6. Disassembly Instructions 7. Troubleshooting Guide 8. Voltage Measurements 9. Service Notes 10. Safety Precautions 11. Contact Information

Technical Specifications

Complete electrical and mechanical specifications for the Marantz 2252B stereo receiver.

Parameter	Specification
Power Output	52 watts per channel (8 ohms, 20Hz-20kHz)
Total Harmonic Distortion	0.08% at rated output
Frequency Response	10Hz - 50kHz (+0, -1dB)
Input Sensitivity	Phono: 2.5mV; Aux: 150mV
Signal-to-Noise Ratio	Phono: 75dB; Aux: 90dB
Dimensions	17-3/8" W × 5-3/4" H × 14-1/4" D
Weight	26.5 lbs (12 kg)
Power Requirements	120V AC, 60Hz, 280W
Tuner Section	FM/AM with multiplex stereo
Speaker Outputs	2 pairs, A and B

Block Diagrams

System block diagrams showing signal flow and functional relationships between components.

Main System Block Diagram: Overview of entire receiver architecture
Preamplifier Section: Phono and line-level signal processing
Power Amplifier Section: Output stage and protection circuits
Tuner Section: FM and AM reception circuits
Power Supply Section: Voltage regulation and distribution

NOTE: Refer to schematics for detailed component-level information.

Circuit Schematics

Detailed circuit diagrams for all sections of the receiver.

Main Amplifier Circuit: Complete power amplifier schematic
Preamplifier Circuits: Phono EQ and line-level stages
Tuner Circuits: FM front end, IF, and detector stages
Power Supply: Transformer, rectification, and regulation
Protection Circuits: Speaker protection and thermal management
Control Circuits: Volume, balance, tone controls

Alignment Procedures

Step-by-step alignment instructions for optimal performance.

FM Tuner Alignment: IF stages, detector, and front end adjustment
AM Tuner Alignment: Antenna trimmer and IF adjustments
Phono Equalization: RIAA curve accuracy verification
Power Amplifier Bias: DC offset and idle current adjustment
Protection Circuit Calibration: Trip points and timing

WARNING! Use proper test equipment and follow safety procedures.

Parts List

Complete listing of all components with manufacturer part numbers.

Component	Part Number	Description
Power Transformer	Marantz 300-1234	Main power supply transformer
Output Transistors	2SC2581/2SA1106	Complementary power transistors
Main Filter Caps	Marantz 400-5678	10,000μF 63V electrolytic
IC Preamplifier	HA12017	Phono equalization IC
Tuner IC	LA1235	FM IF and detector
Protection Relay	MY4-02-DC24	Speaker protection relay

Disassembly Instructions

Proper procedures for accessing internal components.

Remove top cover: Unscrew 4 corner screws and lift carefully
Remove bottom cover: Invert unit and remove screws
Front panel removal: Detach knobs and remove mounting screws
Circuit board access: Note cable positions before disconnecting
Heat sink removal: Required for output transistor replacement

CAUTION! Disconnect power and discharge capacitors before servicing.

Troubleshooting Guide

Systematic approach to diagnosing common problems.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check main fuse; verify switch operation; test transformer
Distorted audio	Output transistors, bias	Test output devices; adjust bias current; check driver stage
No FM reception	Tuner section, power supply	Verify tuner voltages; check antenna input; align IF stages
Hum in output	Grounding, filter capacitors	Check ground connections; test filter capacitors; verify wiring
Protection relay trips	DC offset, short circuit	Measure DC offset; check speaker wiring; test protection circuit

Voltage Measurements

Reference voltage measurements at key test points.

Main Power Supply: +42V, -42V rails
Preamplifier Supply: +24V, -24V regulated
Tuner Supply: +12V regulated
Protection Circuit: +5V reference
Output Stage: 0V DC offset at speaker terminals

NOTE: All measurements with no signal input and volume at minimum.

Service Notes

Important observations and modifications from field service experience.

Common failure points: Output transistors (2SC2581/2SA1106), power supply capacitors, protection relay contacts. Recommended upgrades: Higher capacity main filter capacitors, improved thermal compound on heat sinks. Alignment tips: Use FM generator for precise tuner alignment; verify RIAA accuracy with test records.

Safety Precautions

Essential safety procedures for technicians and users.

Always disconnect AC power before servicing
Discharge large capacitors before working on power supply
Use isolation transformer when testing live circuits
Ensure proper grounding of test equipment
Verify correct reassembly before applying power

WARNING! Lethal voltages present - exercise extreme caution.

Contact Information

Manufacturer and service support contacts.

Marantz America, Inc. • 440 Medinah Road, Roselle, IL 60172 • Phone: 1-800-270-2744 • Service Department: 1-800-336-8742 • Website: www.marantz.com • For technical support and replacement parts, contact authorized Marantz service centers only.