Marantz 1152DC Service Manual

The Marantz 1152DC is a high-performance stereo receiver featuring DC power amplifier circuitry, 32 watts per channel RMS power output, direct-coupled phono equalizer, loudness contour, tape monitor, and tone controls. This service manual provides comprehensive technical information for service technicians, including schematics, alignment procedures, parts list, and troubleshooting guidelines for proper maintenance and repair.

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

Technical Specifications

Complete electrical and mechanical specifications for the Marantz 1152DC stereo receiver.

Parameter	Specification
Power Output	32 watts per channel RMS (8 ohms, 20Hz-20kHz)
Total Harmonic Distortion	0.1% or less at rated output
Frequency Response	10Hz-50kHz (+0, -1dB)
Input Sensitivity	Phono: 2.5mV; Aux: 150mV
Signal-to-Noise Ratio	Phono: 75dB; Aux: 90dB
Tone Controls	Bass: ±10dB at 100Hz; Treble: ±10dB at 10kHz
Power Requirements	120V AC, 60Hz, 180W
Dimensions	17-3/8" W × 5-1/4" H × 13-3/4" D
Weight	21.6 lbs (9.8 kg)

Block Diagram

System block diagram showing signal flow and major circuit sections.

Input Selector: Phono, Aux, Tape 1, Tape 2
Phono Equalizer: RIAA equalization with low-noise transistors
Tone Control: Bass and treble controls with loudness switch
Volume/Balance: Dual concentric controls
Power Amplifier: Direct-coupled complementary symmetry output
Power Supply: Regulated and unregulated supplies
Protection Circuit: Speaker protection relay

NOTE: Refer to schematic diagram for detailed component connections.

Circuit Description

Detailed description of major circuit sections and their operation.

Power Supply: Transformer T001, bridge rectifier, filter capacitors
Phono Stage: Low-noise differential amplifier with RIAA equalization
Preamplifier: Voltage amplifier with tone controls
Power Amplifier: Direct-coupled complementary output stage
Protection Circuit: DC detection and relay delay

CAUTION! High voltages present - discharge capacitors before servicing.

Alignment Procedures

Step-by-step alignment and adjustment procedures.

DC Offset: Adjust VR001/VR002 for 0mV at speaker terminals
Bias Current: Set VR003/VR004 for 20mA across emitter resistors
Phono Equalization: Verify RIAA response with audio generator
FM Tuner: Align IF transformers and adjust tracking (if equipped)

Parts List

Complete list of components with manufacturer part numbers.

Reference	Description	Part Number
Q001-Q004	2SC945 Transistor	MA-1234
Q005-Q008	2SA733 Transistor	MA-1235
C001-C004	47μF 16V Electrolytic	MA-2345
R001-R008	1kΩ 1/4W Resistor	MA-3456
T001	Power Transformer	MA-4567
VR001-VR004	500Ω Trimmer	MA-5678

Schematic Diagrams

Complete schematic diagrams for all circuit sections.

Main Amplifier Schematic: Power amplifier and protection circuits
Preamplifier Schematic: Phono, tone controls, and input switching
Power Supply Schematic: Transformer, rectification, and regulation
Control Section: Switches, indicators, and front panel controls

Tip: Use high-resolution prints for component identification.

PCB Layout

Printed circuit board layouts and component placement diagrams.

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

Power Amplifier Section: Heat sink mounting and output transistor placement

Preamplifier Section: Input jacks and control wiring

Troubleshooting Guide

Systematic troubleshooting procedures for common problems.

Symptom	Possible Cause	Corrective Action
No power	Fuse blown, power switch	Check F001/F002; verify switch continuity
One channel dead	Output transistors, protection relay	Check Q009-Q012; test relay contacts
Distortion	Bias current, DC offset	Adjust VR003/VR004; check emitter resistors
Hum	Grounding, filter capacitors	Check C005-C008; verify ground connections
No phono input	Phono stage, selector switch	Test Q001-Q004; clean selector switch

Service Notes

Important service information and common repair procedures.

Output transistors must be matched and installed with thermal compound
Use original Marantz parts for critical components
Allow proper warm-up time before making adjustments
Document all measurements and adjustments made during service

WARNING! Always use isolation transformer when servicing live chassis.

Safety Precautions

Essential safety procedures for technicians and users.

Always disconnect power before servicing. Discharge large capacitors. Use proper grounding techniques. Follow local electrical codes. Ensure proper ventilation during operation.

CAUTION! Lethal voltages present - qualified technicians only.