Tom, when you loose the tone in the frame, are they any chance that you have vent holes in the frame. If not find where wires come out and start checking there. Also I am sure you have looked for the same color where you loose the tone to where the wires come out of the frame. Ohm from the blown fuse side (fuse removed) to ground and see what you come up with. A lot of wires to check but it can be done. Insure that your battery is off or the fuse is pulled.
If you leave that wire off , what does not work and that gives you place to start.
Gene