I have a MIM P-bass that recently started humming but goes away when touching the strings, bridge or input jack area- obviously some sort of grounding problem. The humming would also go away if I turned down the tone pot just a bit. Today I replaced the stock bridge w/ a new Gotoh 201 bridge. The hum was still there so I wrapped the bridge ground wire around one of the bridge screws, and also shielded the cavity with copper tape at the same time. The humming is gone- BUT- now when I max out the tone pot, all sound disappears. If I back off the tone pot the same distance I used to to get rid of the hum, the sound returns with no hum.I also notice the volume output from the volume knob is lower than it was before the shielding and grounding.Any ideas? Do I need to replace the tone pot? It is a CTS pot, about a year old.