Marantz 5420 Service Manual

The Marantz 5420 is a high-performance stereo receiver featuring advanced audio processing, multiple input/output options, and professional-grade components. This service manual provides comprehensive technical documentation for qualified service personnel, including schematics, alignment procedures, troubleshooting guides, and replacement part information for proper maintenance and repair of the unit.

1. Technical Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Alignment Procedures 5. Disassembly Instructions 6. Troubleshooting Flowcharts 7. Parts List 8. PCB Layouts 9. Wiring Diagrams 10. Safety Precautions 11. Service Notes

Technical Specifications

Complete electrical and mechanical specifications for the Marantz 5420 stereo receiver.

Parameter	Specification
Power Output	80W per channel (8Ω, 20Hz-20kHz)
Total Harmonic Distortion	<0.05% at rated output
Frequency Response	10Hz - 100kHz (+0/-3dB)
Signal-to-Noise Ratio	>100dB (line inputs)
Input Sensitivity	200mV (line), 2.5mV (phono)
Dimensions	440mm W × 150mm H × 380mm D
Weight	12.5kg
Power Requirements	120V/230V AC, 50/60Hz
Power Consumption	280W maximum
Speaker Impedance	4-16Ω compatible

Block Diagrams

System block diagrams showing signal flow and functional relationships between major circuit sections.

Main System Block Diagram: Overview of entire receiver architecture
Power Amplifier Section: Detailed power amplification stages
Preamplifier Section: Input selection and signal processing
Power Supply Section: Voltage regulation and distribution
Tuner Section: RF and IF signal processing blocks

NOTE: All block diagrams include signal flow arrows and voltage test points.

Circuit Descriptions

Detailed explanations of major circuit functions and operational principles.

Power Amplifier Circuit: Complementary symmetry output stage with protection circuitry
Preamplifier Section: Low-noise FET input stages with tone control networks
Phono Equalizer: RIAA equalization with high gain low-noise amplification
Power Supply: Dual secondary transformer with regulated ± supplies
Protection Circuits: DC detection, overcurrent, and thermal protection

Alignment Procedures

Step-by-step alignment instructions for optimal performance.

FM Tuner Alignment: IF transformers, quadrature detector, RF tracking
AM Tuner Alignment: IF alignment, oscillator tracking
Phono Equalization: RIAA response verification and adjustment
Bias Current Adjustment: Power amplifier idle current setting
DC Offset Adjustment: Output DC voltage nulling procedure

WARNING! Use specified test equipment and follow procedures exactly. Incorrect alignment may cause damage.

Disassembly Instructions

Complete disassembly sequence for service access.

Remove top cover: 8 Phillips screws on rear and sides
Remove front panel: 4 screws at top and bottom edges
Main board access: Remove 6 mounting screws and disconnect wiring harnesses
Power supply removal: Disconnect all wires and remove 4 mounting screws
Heat sink assembly: Remove thermal compound and 6 mounting bolts

CAUTION! Discharge power supply capacitors before working on high-voltage sections.

Troubleshooting Flowcharts

Systematic diagnostic procedures for common failure modes.

Symptom	Test Procedure	Likely Cause
No power	Check fuse, power switch, transformer primary	Blown fuse, faulty switch, open transformer
No audio output	Check protection circuit, output transistors	Protection relay, shorted outputs, DC offset
Distorted audio	Check bias current, output stage	Incorrect bias, leaky transistors
No FM reception	Check tuner power supply, local oscillator	Failed tuner IC, open RF coils
Hum/buzz	Check ground connections, filter capacitors	Dry electrolytics, ground loops

Parts List

Complete component listing with manufacturer part numbers.

Transistors: 2SC2878 (output), 2SA968 (driver), 2SK170 (input)
Integrated Circuits: NJM2068 (op-amp), LA1260 (FM IF), TA7343 (MPX)
Electrolytic Capacitors: 10,000μF/63V (main filter), 470μF/35V (decoupling)
Resistors: Metal film 1%, specified wattages
Transformers: Power: PM-45, Output: TO-252

PCB Layouts

Printed circuit board patterns and component placement guides.

Main Amplifier Board: Component side and solder side views
Power Supply Board: Component placement and trace routing
Preamplifier Board: Input switching and tone control sections
Tuner Module: RF and IF circuit board layout
Front Panel Board: Display and control interface

NOTE: All layouts include reference designators matching schematics.

Wiring Diagrams

Complete interconnecting wiring and harness routing.

Includes:

Main harness connections between boards
Front panel control wiring
Speaker output and input jack wiring
Power supply distribution wiring
Grounding scheme and star ground points

Tip: Verify all connections against diagram before power application.

Safety Precautions

Essential safety procedures for service personnel.

Always disconnect AC power before servicing. Use isolation transformer when testing live circuits. Beware of high voltages in power supply and amplifier sections. Ensure proper grounding of test equipment. Follow ESD precautions when handling semiconductors.

WARNING! Lethal voltages present. Only qualified technicians should perform service.

Service Notes

Additional technical information and service tips.

Service Bulletin	Description	Application
SB-5420-01	Improved heat sink compound application	All units after serial #M5420-8500
SB-5420-02	Output transistor mounting torque specification	All production units
SB-5420-03	FM alignment procedure update	Units manufactured before 1998
SB-5420-04	Power supply capacitor lifetime notice	Units in service >15 years
SB-5420-05	Protection circuit timing adjustment	Specific to units with relay chatter

Technical Support: Contact Marantz Service Department for latest updates.