@rottalpha @Goldie99 Thanks for drawing my attention to the ongoing work on the Sony TA-F5A. Apparently, he was/is struggling similar problems including how to get the PS PCB out of its casing. Funny story. True, it's Indiana Jones-like experience.
Earlier I used the DIRECT output and it was then that the left channel gave out the "big shot sound" every once in a while. Immediately after the shot sound, the output got "muted", I believe only on that channel. I usually just jumped to the amp and turned it off and waited a few seconds, sometimes minutes, and then turned it back on. Then it either turned on and I heard a clicking sound after which it worked, or it did not give a clicking sound and it did not work. If the latter happened, I turned it off again and just waited longer to turn it back on again. Sometimes it took many minutes to be able to get it work again.
Recently, however, perhaps the last few weeks, I switched over to the C COUPLED output and the "big shot sound" never happened again. Sometimes, though, I heard a slight buzzing from the speakers that went away in seconds. But the amp never shut down again. Then the R401 "broke" into two pieces not long ago while the amp was open and the PS case was separated from the rest of the amp (except for the two wire connections). And now I am waiting for the resistor to arrive form China.
Other peculiarity is that the amp has a slight and constant white noise sound, which is odd as it is supposed to be one of least noisy ones (S/N ratio > 120 dB). It is indeed slight but still audible on soft classical music or with no music.
Heatwise, I noticed while the amp was open, and I was using it in class B mode that the right power FETs were very hot, while the left ones were just warm, not hot at all. Weird. I noticed this only after I started playing with setting the 90 V right (it was 94 V before I opened the amp) and the bias currents. I more or less managed to get the 20 and 350 mA's for class B and A, respectively. The PLPS also heated up after a while.
Earlier I used the DIRECT output and it was then that the left channel gave out the "big shot sound" every once in a while. Immediately after the shot sound, the output got "muted", I believe only on that channel. I usually just jumped to the amp and turned it off and waited a few seconds, sometimes minutes, and then turned it back on. Then it either turned on and I heard a clicking sound after which it worked, or it did not give a clicking sound and it did not work. If the latter happened, I turned it off again and just waited longer to turn it back on again. Sometimes it took many minutes to be able to get it work again.
Recently, however, perhaps the last few weeks, I switched over to the C COUPLED output and the "big shot sound" never happened again. Sometimes, though, I heard a slight buzzing from the speakers that went away in seconds. But the amp never shut down again. Then the R401 "broke" into two pieces not long ago while the amp was open and the PS case was separated from the rest of the amp (except for the two wire connections). And now I am waiting for the resistor to arrive form China.
Other peculiarity is that the amp has a slight and constant white noise sound, which is odd as it is supposed to be one of least noisy ones (S/N ratio > 120 dB). It is indeed slight but still audible on soft classical music or with no music.
Heatwise, I noticed while the amp was open, and I was using it in class B mode that the right power FETs were very hot, while the left ones were just warm, not hot at all. Weird. I noticed this only after I started playing with setting the 90 V right (it was 94 V before I opened the amp) and the bias currents. I more or less managed to get the 20 and 350 mA's for class B and A, respectively. The PLPS also heated up after a while.
