My parents have a Harman Kardon AVS 435 running their multi-room system in their house. It worked great for a few years. One day, whenever you turned it on, a terrible screeching sound came from the speakers. Couldn't get music to play, couldn't get the screeching to stop. Then, one day, the screeching stopped, but music still won't play.
I have been trying to help them with this, but I am in way over my head. I checked the "brain" down in their basement. Way over my head. I say a panel with two lights: one was green and lit up and the word next to it was "STAT". The other light was red, not lit, and had "IR" next to it.
It's an A-BUS set up.
The speakers will pop when the volume knobs are toggled in different rooms. If I unplug the AVS435 and plug it back in, it starts up in standby mode and the speakers hum until I fully power the unit on.
So. I have no idea if the issue is with the Harman, or if it is something going on amidst all the wires down in their basement.