Or try one of the Rothwells.
Printable View
Or try one of the Rothwells.
Could be the earth lead has come loose inside, worth having a look. Stick some internal photos up here if you like.
Sending a PM.
Oh, what I have come across before (and quite possible what Alan has suggested in his PM) is, when removing the RCA cable it’s easy to twist the plug and this can cause the socket to also twist. When this happens the positive and return wires can touch inside the unit where they are soldered to the RCA sockets. I’ve also seen something similar happen with the ground connection - all easy, quick and cheap fixes.