Marantz 2218 Service Manual

The Marantz 2218 is a classic stereo receiver featuring 18 watts per channel RMS power output, FM/AM tuner with quartz PLL synthesizer tuning, loudness contour, tape monitor, headphone jack, and comprehensive tone controls. This service manual provides detailed technical information for service technicians including schematics, alignment procedures, parts lists, and troubleshooting guides for the Marantz 2218 stereo receiver.

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

Technical Specifications

Complete electrical and mechanical specifications for the Marantz 2218 stereo receiver.

Parameter	Specification
Power Output	18W per channel RMS (8Ω, 20Hz-20kHz)
Total Harmonic Distortion	0.08% at rated output
Frequency Response	10Hz-50kHz (+1/-3dB)
Input Sensitivity	Phono: 2.5mV; Aux: 150mV
Signal-to-Noise Ratio	Phono: 70dB; Aux: 90dB
Tuning Range	FM: 87.5-108MHz; AM: 530-1620kHz
Capture Ratio	1.5dB
Image Rejection	70dB
Power Requirements	120V AC, 60Hz, 65W
Dimensions	17-1/4" W × 4-3/4" H × 12-3/4" D

Block Diagram Overview

System block diagram showing signal flow and major circuit sections.

Tuner Section: FM front end, IF amplifier, MPX decoder
Preamplifier: Phono equalization, tone controls, selector switching
Power Amplifier: Driver stage, output transistors, protection circuit
Power Supply: Transformer, rectifier, filter capacitors, regulators
Control Circuits: Volume, balance, tone, loudness, muting

NOTE: Refer to schematic diagrams for detailed circuit connections.

Circuit Description

Detailed explanation of major circuit sections and their operation.

FM Tuner: Uses TA7303P IC for FM front end with varactor diode tuning
IF Section: Ceramic filters at 10.7MHz with LA1231N IF amplifier IC
MPX Decoder: LA3401 IC for stereo decoding with 19kHz pilot cancellation
Phono Preamp: Discrete transistor design with RIAA equalization
Tone Control: Baxandall-type bass and treble controls
Power Amplifier: Complementary symmetry output stage with 2SD438/2SB568 transistors
Protection Circuit: DC detection and relay delay for speaker protection

Alignment Procedures

Step-by-step alignment instructions for proper receiver performance.

FM IF Alignment: Adjust IF transformers for maximum output at 10.7MHz
FM Oscillator Alignment: Set oscillator trimmer for proper frequency coverage
FM Front End: Adjust RF amplifier and mixer coils for best sensitivity
Stereo Decoder: Adjust separation control for maximum stereo separation
AM Alignment: Adjust oscillator and antenna trimmers for proper tracking
Dolby NR: Adjust level and bias for proper Dolby operation (if equipped)

CAUTION! Use proper test equipment and follow safety procedures.

Parts List

Complete listing of components with manufacturer part numbers.

Component	Part Number	Description
Output Transistors	2SD438/2SB568	Complementary power transistors
FM IF IC	LA1231N	FM IF amplifier and detector
MPX Decoder IC	LA3401	Stereo multiplex decoder
Power Transformer	700-2218-10	Main power transformer
Main Filter Caps	4700μF/50V	Power supply filter capacitors
Tuning Capacitor	700-2218-20	FM/AM tuning capacitor assembly
Relay	MY4-02DC24	Speaker protection relay

Schematic Diagrams

Complete schematic diagrams for all circuit sections.

Main Amplifier Schematic: Power supply and audio output stages
Preamplifier Schematic: Phono, aux, and tone control circuits
FM Tuner Schematic: RF, IF, and detector circuits
AM Tuner Schematic: AM receiver section
Control Schematic: Selector switches, volume, and balance controls
Power Supply Schematic: Transformer, rectifiers, and regulators

Note: Schematics show component values and test points.

PCB Layouts

Printed circuit board layouts and component placement guides.

Main Board: Component side and solder side views with reference designators

Tuner Board: FM/AM tuner module layout and component locations

Control Board: Front panel controls and switch assemblies

Tip: Use layout diagrams for component replacement and trace repair.

Troubleshooting Guide

Systematic approach to diagnosing and repairing common problems.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check fuse F801; test power switch; measure transformer output
No audio output	Protection relay, output transistors	Check relay operation; test output transistors for shorts
Distorted audio	Bias adjustment, leaky capacitors	Adjust bias current; replace leaky coupling capacitors
No FM reception	Tuner power, IF alignment	Check +12V to tuner; realign IF stages
No stereo separation	MPX decoder, 19kHz adjustment	Adjust stereo separation control; check LA3401 IC
Hum in audio	Ground loops, filter capacitors	Check ground connections; replace main filter capacitors

Service Notes

Important service information and common repair procedures.

Bias Adjustment: Set to 20mA across emitter resistors with no signal
DC Offset: Adjust for 0V DC at speaker terminals
Transistor Replacements: Use original or approved substitutes
Capacitor Replacement: Replace electrolytic capacitors showing leakage
Cleaning: Use contact cleaner on controls and switches
Test Points: Voltage measurements at key test points provided

Safety Precautions

Essential safety information for service personnel.

WARNING! High voltages present - discharge power supply capacitors before servicing. Use isolation transformer when working on live circuits. Follow proper grounding procedures. Replace safety critical components with exact replacements.

Service Documentation: For additional service information contact Marantz Technical Support or authorized service centers.