This sounds like a ground loop problem. Search this board (or others) to find exactly how to fix it, I think the general rule is that you only want to have one 3-pronged plug going into the wall. I had a very similar problem and this turned out to be the cause.
Tube testers can be bought on eBay, they run about $40 and up depending on what you get. Mine came from my grandfather, who bought it at an auction for a buck or so and then gave it to me.
Hope that helps
Gary
Tube testers can be bought on eBay, they run about $40 and up depending on what you get. Mine came from my grandfather, who bought it at an auction for a buck or so and then gave it to me.
Hope that helps
Gary