Marantz SR 680 Service Manual

The Marantz SR 680 is a high-performance AV receiver featuring Dolby Digital and DTS decoding, 5.1 channel surround sound, 80 watts per channel, multiple audio/video inputs, digital optical/coaxial inputs, AM/FM tuner, preamp outputs, speaker A/B switching, and advanced DSP modes. This service manual provides technical specifications, circuit diagrams, troubleshooting guides, and repair procedures for qualified service technicians.

Technical Specifications

Complete technical specifications and performance characteristics of the Marantz SR 680 AV receiver.

Block Diagrams

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

1. Main System Block Diagram: Overall signal path from inputs to outputs
2. Power Supply Block Diagram: AC to DC conversion and distribution
3. Audio Processing Block: DSP and decoding circuitry
4. Video Processing Block: Video switching and processing
5. Tuner Block Diagram: AM/FM reception and processing
6. Microprocessor Control: System control and user interface

WARNING! These diagrams are for qualified technicians only. Do not attempt repairs without proper training.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

• Power Supply Circuit: Switching power supply with ±12V, ±35V, and +5V outputs
• Main Amplifier Circuit: Discrete power amplifier stages with protection circuitry
• Digital Audio Circuit: Crystal CS492304 Dolby Digital/DTS decoder
• Analog Audio Circuit: NJM2068 op-amps for input buffering and processing
• Video Circuit: NJM2248 video switches and buffers
• Microprocessor Circuit: HD6437049F28V microcontroller with 128KB ROM
• Tuner Circuit: LA1266 FM IF and LA3401 MPX decoder
• Protection Circuit: DC detection, overcurrent, and thermal protection

Disassembly Procedures

Step-by-step instructions for safely disassembling the receiver.

1. Remove top cover: Remove 6 Phillips screws from rear and sides
2. Remove front panel: Disconnect ribbon cables and remove 4 screws
3. Remove main board: Disconnect all connectors and remove 8 mounting screws
4. Remove power supply board: Discharge capacitors and remove 4 screws
5. Remove amplifier heatsink: Remove thermal compound and 6 mounting screws
6. Remove tuner assembly: Remove shield and 3 mounting screws

CAUTION! Always disconnect AC power and discharge large capacitors before disassembly.

Alignment & Adjustment

Factory alignment procedures and adjustment points.

Test Points & Measurements

Critical test points and expected voltage measurements.

• TP1: +12V analog supply - should measure 12.0V ±5%
• TP2: -12V analog supply - should measure -12.0V ±5%
• TP3: +35V amplifier supply - should measure 35.0V ±5%
• TP4: -35V amplifier supply - should measure -35.0V ±5%
• TP5: +5V digital supply - should measure 5.0V ±3%
• TP6: System clock - should measure 16.9344MHz ±10ppm
• TP7: Microprocessor reset - should measure 4.5V minimum
• TP8: Protection circuit - should measure 0V in normal operation

Parts List

Complete list of components with manufacturer part numbers.

PCB Layouts

Printed circuit board layouts and component placement diagrams.

1. Main Board (PWB-A): Top and bottom layer views with component designations
2. Power Supply Board (PWB-B): Component placement and trace routing
3. Front Panel Board (PWB-C): Display and control circuitry layout
4. Tuner Board (PWB-D): RF and IF section component placement
5. Amplifier Board (PWB-E): Power amplifier and protection circuit layout

Note: All layouts shown at 1:1 scale for accurate component identification.

Troubleshooting Flowcharts

Systematic troubleshooting guides for common problems.

Safety Precautions

Critical safety information for service personnel.

• Always disconnect AC power before servicing
• Discharge large capacitors (>100μF) before working on power supply
• Use isolation transformer when testing primary side circuits
• Replace safety critical components (fuses, safety capacitors) with identical parts
• Ensure proper grounding of test equipment and workbench
• Check for overheating components and proper heatsink mounting
• Verify all safety certifications after repair (UL, CSA, CE)

WARNING! Lethal voltages are present in the power supply section. Exercise extreme caution.

Schematics

Complete circuit schematics for all major sections.

1. Main System Schematic: Overall system interconnections
2. Power Supply Schematic: AC input to DC output circuits
3. Amplifier Section: Power amplifier and protection circuits
4. Audio Processing: Digital and analog audio processing
5. Video Section: Video switching and processing circuits
6. Tuner Section: AM/FM tuner and IF processing
7. Control Section: Microprocessor and user interface
8. Display Section: Front panel display and controls

Note: Schematics are drawn to JIS standards with Japanese and English annotations.