Hello all. I have an old Tannoy TFX sub that I was hoping to bring out of retirement for a secondary cinema set up. Problem is, upon plugging in, there's no sound not even a low hum. The red light comes on in 'off and Auto' position, but switching to On there's no green light. I've tried it with 2 av amps, changed the internal fuse with no joy. And ideas I could try before I have to shell out for a replacement?