Marantz 1070 Service Manual

The Marantz 1070 is a classic stereo receiver from the 1970s featuring 35 watts per channel RMS, solid-state circuitry, phono inputs for MM cartridges, tape monitor, loudness contour, and tone controls. This service manual covers technical specifications, circuit diagrams, alignment procedures, troubleshooting, and maintenance guidelines for qualified service technicians.

1. Technical Specifications 2. Block Diagram 3. Circuit Description 4. Alignment Procedures 5. Parts List 6. PCB Layouts 7. Schematics 8. Troubleshooting Guide 9. Service Adjustments 10. Safety Precautions 11. Contact Information

Technical Specifications

Detailed electrical and mechanical specifications for the Marantz 1070 stereo receiver.

Parameter	Specification
Power Output	35 watts per channel RMS (8 ohms, 20Hz-20kHz)
Total Harmonic Distortion	0.3% maximum at rated output
Frequency Response	10Hz-50kHz (+1, -3dB)
Input Sensitivity	Phono: 2.5mV; Aux: 250mV
Signal-to-Noise Ratio	Phono: 70dB; Aux: 90dB
Tone Controls	Bass: ±10dB at 100Hz; Treble: ±10dB at 10kHz
Power Requirements	120V AC, 60Hz, 200 watts
Dimensions	17-1/4" W × 5" H × 14-1/2" D
Weight	22 lbs (10 kg)
Speaker Impedance	4-16 ohms

Block Diagram

System overview showing signal flow through the Marantz 1070 receiver.

Input Selector: Phono, Aux, Tape
Phono Preamp: RIAA equalization
Tone Control: Bass and treble circuits
Volume/Loudness: Attenuation and compensation
Power Amplifier: Driver and output stages
Protection Circuit: DC detection and relay
Power Supply: Transformer and rectification

NOTE: Refer to schematic diagrams for detailed circuit connections.

Circuit Description

Detailed explanation of major circuit sections in the Marantz 1070.

Power Supply: Dual secondary transformer with bridge rectifier
Phono Stage: Differential amplifier with RIAA equalization
Preamplifier: High-gain voltage amplifier with tone controls
Power Amplifier: Complementary symmetry output stage
Protection Circuit: Transistor-based DC detection and relay drive

CAUTION! High voltages present in power supply section.

Alignment Procedures

Step-by-step adjustment procedures for optimal performance.

DC Offset: Adjust VR301/VR302 for 0mV at speaker terminals
Bias Current: Set VR303/VR304 for 20mA across emitter resistors
Phono Equalization: Verify RIAA curve with audio generator
FM Alignment: Requires specialized test equipment

Parts List

Complete component listing with manufacturer part numbers.

Reference	Description	Part Number
Q101-Q104	2SC458LG transistors	Marantz 458-001
Q701-Q704	2SC1116A output transistors	Marantz 1116-002
C201-C204	47μF 16V electrolytic	Marantz ELC-047-16
R101-R104	4.7kΩ 1/4W resistor	Marantz RES-4K7
VR301-VR304	500Ω trimmer potentiometer	Marantz POT-500

PCB Layouts

Printed circuit board patterns and component placement diagrams.

Main Amplifier Board: P700
Preamplifier Board: P400
Power Supply Board: P800
Control Board: P300

Tip: Use exact replacement components to maintain performance.

Schematics

Complete circuit diagrams for all sections of the receiver.

Main Schematic: Overall system diagram
Power Amplifier: Output stage and protection
Preamplifier: Phono and line stages
Power Supply: Transformer and regulation
Control Circuits: Selector switches and tone controls

WARNING! Schematics show lethal voltages - exercise extreme caution.

Troubleshooting Guide

Common problems and solutions for the Marantz 1070.

Symptom	Possible Cause	Corrective Action
No sound	Protection relay not engaging	Check DC offset; replace output transistors
Distortion	Bias current incorrect	Adjust VR303/VR304; check driver transistors
Hum	Power supply ripple	Replace filter capacitors C801-C804
Intermittent operation	Cold solder joints	Resolder all connections on main board
One channel dead	Failed output transistor	Replace complementary pair Q701-Q704

Service Adjustments

Routine maintenance and calibration procedures.

Bias Adjustment: Measure across R731/R732, adjust for 20mA
DC Balance: Adjust VR301/VR302 for 0V at output
Cleaning: Deoxit on all controls and switches
Thermal Compound: Replace on output transistors

Safety Precautions

Essential safety information for service technicians.

DANGER! Lethal voltages present even when unplugged. Always discharge power supply capacitors before servicing. Use isolation transformer when working on live circuits. Follow proper grounding procedures.

Contact Information

Marantz service centers and technical support resources.

Marantz America: 1-800-270-2059. Original manufacturer: Superscope Inc. For genuine replacement parts and factory service, contact authorized Marantz service centers. Technical documentation archived at Marantz historical society.