Sony STR-AV780 is a combined receiver and audio/video control center. This receiver is manufactured by Sony in around 1986 and it is capable to deliver 2 × 80W audio output power with 8Ω speaker load. The STR-AV780 which I got had two problems. The first problem is in the power amplifier stage and it produces distortion in high frequencies. The second problem is in FM radio receiver and it is completely dead. The power amplifier of STR-AV780 is based on two Sanyo STK4042 XI AF power amplifier ICs. To fix the distortion issue we replace all the electrolytic capacitors in both STK4042 power amplifier boards. After replacing capacitors distortion issue got fixed and the power amplifier starts to produce a clear output waveform. The FM receiver of this AVR is mainly based on 2 ICs. For IF stage it uses LA1235, and to demodulate FM stereo signal it uses LA3401. Apart from that Sony CX7925 is used as PLL frequency synthesizer. The front end of FM tuner is based on a couple of transist
This blog contains electronic, amateur radio, and embedded system projects, which I did during my free time. Unless otherwise noted, all the articles and projects described on this blog are based on my original designs.