Hi Michael and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, have you tried unplugging the B&K AVR307 for an extended period of time? ...and then plugging back in using a different outlet?
Appreciate the information on what has been tried.
How long has the B&K been in use please?
Have you checked the speakers and the wiring at the back of the AVR307?
A final try please; have you considered / performed a RESET?
Consider a RESET. A reset is both a test and a try of a fix. As it implies, a reset would force the unit to revert back to factory defaults removing glitches and config errors but would include memories, presets and user preferences. After a reset, the initial setup would have to be performed. If have not been done and should you venture to try: Please click HERE.
May have to be done a number of times.
This is very critical - a reset however would not be corrective of an internal hardware concern; but it would be confirmed. In some instances, it may even expose / cause other issues.
Any update Michael?
If all external factors have been checked and ruled out, then the described symptom and if non-corrective result of a RESET would almost always point to an internal hardware issue. This would then require that the unit be opened up for visual inspection, voltage/continuity/resistance checks, confirm faults and effect repairs.
Are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter and even perhaps a soldering iron?