Sony STR-DE197 Right side speakers, A&B, entire right side channel dropped out

SO the whole right side just dropped out, with no other changes both speakers A&B. I have a service manual coming, but I was wondering if anyone else has ever had that happen and can point me in a direction of an offender so I'm not spending days tracing circuits in this baby. If ya have anything good for me, please holla back. I'd sure appreciate your valuable time. I've done all the factory resets I could think of already, so I doubt something just "got stuck" in it's little brains, must be something mechanical cuz it's both A&B. Let me know if you have the goods   ✌️