Thanks for the replies, guys, I've unscrewed the female jack assembly and there are three contacts (look like bent metal strips) around the place where jack plugs in. When I press the first one (the one closest to the entry point), the green light goes out. I guess this contact needs to be closed when the jack is out, thus turning the guitar off, and mine had become loose. Can anyone confirm that this is correct, and I'm not just short-circuiting my Variax? :) Really appreciate your help!