Debuzzing a Wheaton TriPlanar problem

RFI/EMI problems at tonearm wires can tend to jump around unpredictably as you describe and vary in proximity with the human body. Grounding the tonearm or TT is sometimes not enough, and screened tonearm wire may be necessary to resolve the problem.

Does the hum continue when the cartridge pins are disconnected from the tonearm wires?

You might experiment by relocating the TT to another part of the room. The current location may be in a bad RFI field or too close to in-wall AC wiring or to the AC PS of another component.

Dr John, each tonearm wire conductor that I use to eliminate hum is separately shielded("screened".) In a fully balanced configuration, each shield floats at the cartridge pin and is tied to preamp ground at the other end of the phono cable. In an RCA configuration the braided sheild can be employed both as a shield and as a conductor from the negative cartridge pin. Conductor and braided shield are both 4N silver and very thin. Of course this requires rewiring of tonearm.

Similar to your set-up, the TT is located against a wall that contains AC wiring and is some six feet from the AC main panel in the basement below. The hum increases after switching on a near-by ceiling light. After relocating the TT the hum problem was resolved without the screened wire. Then after adding the screened wire it was possble to return the TT to its former location. The relocation experiment is worth a try, if nothing else to eliminate a significant variable from the problem. Buy some cheap long Radio Shack ICs and just try it on the floor.