I have a NAD 317 amp whose "Protect" light came on a month or so ago. I took it in to my stereo shop (very well respected in the city, been in business for over 60 years) and they were able to repair it. When I brought it home, however, it started to behave oddly.
After 20 minutes or so of being turned on, loud "pops" would come from both speakers; the frequency was quite regular, around 7-10 seconds between instances.
I'm probably not describing them well when I say "pop"; it's more like two deep thuds. Thud-thud...7-10 second pause...thud-thud...another 7-10 second pause, etc. When I turn it off and back on, it repeats again after about 20 minutes.
I took it back to the store, but they said that they were unable to replicate the issue, so they suggested that I check the inputs. I brought it back home, turned it on by itself (i.e. I left the tuner and CD turned off) and again, after 20 minutes the popping began...so much for the inputs!
Does anyone have any idea what this could be?? It seems pretty obvious to me that there is something wrong with the amp and I was hoping that someone out there who is more knowledgable than I could help me get to the bottom of this.