On Thu, 6 Jun 2019 06:14:14 -0700 (PDT), wrote:

I have the same problem, Sony reciever str-av570, that keeps going into protect mode intermittently, even when the reciever is off, will intermittently do relay click and loudness amber led(s) on the front will glow gradually, off, and repeat till I unplug it. Back in 2003-2004, I took my reciever to a authorized sony service center that did not know how to fix it, but charged me $35 to inspect device anyways. From the replies on this post, looks like a good place to start. Thanks for sharing!
Common problem back in the day. Solder a wire from the front panel
circuit board ground to the main board ground and another to the metal
chassis. Tighten all board screws. (Did warranty work for Sony Audio)