I have a Sony receiver ( model number does not matter ). Here is the story: I got this from a friend who said it was not working, so gave it to me for free. I would turn it on and after a minute or two, it would flash "protect" and click the output off. I have a degree in electronics so I did some troubleshooting - I am not sure about all Sony receivers but the components such as transistor chips and even some resistors would get VERY hot - way hotter than they should. What was happening was the heat was changing the characteristics of these components and causing problems. One IC chip in particular was getting so hot I could not touch it -this was the component causing the "protect". The solder joint contacts on the circiut board were not too, bad but I resoldered them with good quality solder, but one pin on the chip itself was the issue -it had a hairline crack on the pin itself, so when it was cold, it worked and when it heated up it totally seperated. This sent the chip into a "short out" state and triggered the "porotect". I did not use any of Sony's scematics, but I believe this chip is a preamp chip. It is easy to spot -it is completely square and stands straight up from the board and is located about an inch-and-a-half from the amplifier chips on the heat sink. I made a heat sink (out of aluminum) just for this chip, and after repairing the bad pin, I no longer have any issues with this receiver - I have had it for about 10 years and it still works great and CRANKS!
That's very interesting. Neither this chip nor any other semiconductor needed to be replace after being heated up like that? How about resistors and capacitors connected to the chip, especially in line with the power supply?