JDA. I've been/am there. Replaced a tether and it did nothing. Per Barry's recommendation, you have to get into the loco and check the wires on the tether socket. Somewhere Barry has posted details of these connections and resoldering them. This is apparently the most common cause, but not easy to access.. If the sounds used to work correctly, then the wiring connections in the tender must all be correct---relocating them is looking for trouble.
If you want to spend all that money, you may hit pay dirt, or you may not. I suppose you could order a new loco harness with socket, but I bet it's not cheap.
