This comprehensive service manual provides detailed technical information for the Yamaha R-V503, R-V703, RX-V393, and RX-V493 receivers. It includes circuit diagrams, component identification, troubleshooting guides, and repair procedures, enabling technicians to diagnose and repair these receivers effectively. The manual covers various aspects of the receivers' operation, including power supply, amplification, audio processing, and user interface. It also provides information on safety precautions, testing procedures, and common issues encountered with these models.