Don't know, but more than likely, once you open them up, the warranty is void. They said that they tested them, but if they didn't install them to a control surface, then I don't consider that a real test. If you power them up on the bench, they don't shake. Its only when they are installed. I'll see what the story is tomorrow. I'll be happy if they strike the charge from my credit card and I'll trash can them. Joe