I recently found an old Pioneer VSX-3300 receiver in my basement. It's got some issues with the left and right channels cutting in and out, but otherwise it's fine. I opened it up and took a look, and found these greenish-yellow splotches on the underside of the PCB:       I've done some...

Hello all,   I'm a years-long lurker coming out from hiding, and this is my very first thread (so please forgive me if this is a dumb question)! Thanks in advance for your patience and help.   First, my audio-snobbery background: I have a small budget so all of my equipment is around $100 or...