My beloved NAD AV716 goes into Protect mode about a minute after switching on. Disconnected all but main speakers and still does it. Switched to an input which has nothing connected and does it still. Next step, Diagnose DSP, Caps, etc. If I can’t diagnose repair myself, I will get a pro repair. If you don’t know, these AV Receivers are amazing for stereo music. Hope she’s back to normal soon.