I have a standard 1/8" phono to RCA cable that I use to connect my mp3 player to my receiver. Last night when I moved the cable it fell behind the receiver and shorted to something. There were big blue sparks and a loud POPs that came through the speakers. I immediately turned the receiver off. There is a melted spot on the ground contact on the 1/8" phono plug but I don't see where it touched on the receiver. I also do not see any place where it could have touched 110V AC. No fuses blue and the receiver seems to work ok. More importantly, my speakers are OK.
I have seen where you can get AC on the chases if the AC plug is wired wrong. This can cause problems when connecting other components.
I may have just answered the question I was about to ask as I recently added a thrift store turntable and I am not convinced that it has the correct power cable.
I took measurements between the ground contact and various places on the receiver using a multi-meter but found no issue. For now I removed the receiver from the system to check it further. Any ideas on what else to check?