Marantz 1180DC Service Manual

The Marantz 1180DC is a high-performance stereo receiver featuring Dolby Surround processing, DC power amplifier design, 80 watts per channel RMS power output, quartz synthesizer tuner, multiple audio inputs/outputs, and comprehensive control capabilities. This service manual provides detailed technical information for service technicians, including schematics, alignment procedures, troubleshooting guides, and replacement parts lists.

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

Technical Specifications

Complete electrical and performance specifications for the Marantz 1180DC stereo receiver.

Parameter	Specification
Power Output	80W per channel RMS (8Ω, 20Hz-20kHz)
Total Harmonic Distortion	0.02% at rated output
Frequency Response	5Hz-50kHz (+0/-3dB)
Input Sensitivity	Phono: 2.5mV; AUX: 150mV
Signal-to-Noise Ratio	Phono: 76dB; AUX: 100dB
Tuner Section	Quartz PLL synthesizer
Tuning Range	FM: 87.5-108MHz; AM: 530-1710kHz
Power Supply	120V AC, 60Hz, 450W max
Dimensions	458W × 150H × 385D mm
Weight	15.8 kg

Block Diagram Overview

System block diagram showing signal flow and major circuit blocks.

Input Selector: Phono, AUX, Tuner, Tape 1, Tape 2
Phono Equalizer: RIAA equalization circuit
Tone Control: Bass, Treble, Loudness controls
Power Amplifier: DC coupled power amplifier stage
Protection Circuit: Speaker protection and thermal shutdown
Power Supply: Regulated power supply with large transformers
Tuner Section: FM/AM tuner with quartz synthesizer

NOTE: Refer to schematic diagrams for detailed circuit connections.

Circuit Description

Detailed description of major circuit sections and their operation.

Power Amplifier Circuit: DC coupled design with complementary symmetry output
Phono Equalizer: High-gain low-noise amplifier with RIAA equalization
Tone Control: Active bass and treble controls with selectable turnover frequencies
Power Supply: Dual secondary transformer with regulated and unregulated supplies
Protection Circuit: DC detection, overcurrent protection, and thermal shutdown
Tuner Circuit: PLL synthesized tuning with ceramic filters and IC demodulation

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

Alignment Procedures

Step-by-step alignment procedures for optimal performance.

FM Tuner Alignment: IF alignment, discriminator adjustment, oscillator tracking
AM Tuner Alignment: IF alignment, oscillator tracking adjustment
Phono Equalization: RIAA equalization accuracy verification
Power Amplifier: DC offset adjustment, bias current setting
Meter Calibration: Power meter and tuning meter calibration

Troubleshooting Guide

Systematic troubleshooting procedures for common problems.

Symptom	Possible Cause	Corrective Action
No power	Fuse, power switch, transformer	Check main fuse F801; verify power switch operation; test transformer primary
No audio output	Protection circuit, amplifier stage	Check protection relay; measure DC offset; test output transistors
Distorted sound	Bias current, output devices	Adjust bias current; check output transistors for leakage
No FM reception	Tuner section, antenna	Verify antenna connection; check tuner IC supply voltages
Hum in audio	Grounding, power supply	Check ground connections; test power supply ripple

Parts List

Complete list of replacement parts with manufacturer part numbers.

Part Number	Description	Qty
2SC2344	Output Transistor NPN	2
2SA1011	Output Transistor PNP	2
HA12016	Dolby Processor IC	1
LA1265	FM/IF Amplifier IC	1
F801	Main Fuse 5A	1
F802	Protection Fuse 3.15A	1

NOTE: Use only manufacturer specified replacement parts.

Schematic Diagrams

Complete schematic diagrams for all circuit sections.

Main Amplifier Circuit: Power amplifier and protection circuits
Pre-amplifier Section: Phono equalizer, tone controls, input selector
Power Supply: Transformer, rectifiers, regulators
FM Tuner: RF amplifier, mixer, IF stages, demodulator
AM Tuner: RF and IF stages, detector
Control Circuits: Input switching, mode selection, indicator circuits

CAUTION! Schematics show actual voltages; verify with high-impedance meter.

Mechanical Information

Mechanical drawings and assembly information.

Chassis Dimensions: Detailed mechanical drawings
PCB Layouts: Component placement and routing
Heat Sink Assembly: Thermal management system
Front Panel: Control layout and mechanical assembly

Rear Panel: Connector placement and mounting

Service Notes

Important service notes and technical updates.

Service Bulletin 1180DC-1: Updated bias adjustment procedure for improved thermal stability. Service Bulletin 1180DC-2: Modified protection circuit timing for faster response. Always check for latest service bulletins before beginning repair work.

Safety Precautions

Critical safety information for service personnel.

WARNING! Lethal voltages present even when unit is disconnected from AC power. Always discharge power supply capacitors before working on unit. Use isolation transformer when servicing live circuits. Follow all safety procedures outlined in this manual.

Service Contacts: Authorized Marantz service centers only. For technical support, contact Marantz service department.

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