Hey all. I was helping a friend set up a home theater system that he has had for 4 years and has never been properly calibrated. His receiver (Integra 30.6) was emitting a buzzing sound from the unit itself (not from the speakers). The unit buzzed consistently as long as it was plugged in, even with power off. Magically, it had stopped by the time I left, but I didn't do anything to fix it. Apparently, it had been happening for a week or two. Receiver works normally otherwise.\n\nAny idea what the cause may have been in case it comes back? I assumed originally it was maybe a power supply issue since it happened even while the unit was off, but not sure why it stopped. \n\nAll advice appreciated!