Debuzzing a Wheaton TriPlanar problem

Yes, Lewm, the hum disappears when I grasp the covered portion of the tube. Sometimes the hum is amplified when I grasp the finger rest at the cartridge end; release the grasp, and no hum. This has been a problem since day one of installation, and several well-known analog experts and reviewers have applied various fixes, including triple-grounding the whole TT setup, wrapping the pre-amp in -yes-a chicken wire cage, and finally purchasing and inserting a $3K passive-step-up device in the chain prior to pre-amplification in order to permit such minimal gain that the hum will not be heard.
All this effort, no success.
And so, with the original dealer out of business and the non-communicative Wheaton lineage located thousands of miles away from NYC, it seems that I possibly purchased a defective tonearm, one which is not all that 'world-class precise' and which probably at this point cannot be righted.
But I do appreciate your insight and experience, Lewm. There is some solace at least in identifying the problem, though no solution seems possible.

Wow! Why so glum? Send it back to Tri, and he can tighten up the bearings to restore the proper ground connection, if that really is the issue, which I am beginning to believe it is. None of the strategies you mention could be expected to cure that problem. Just explain the symptom to him, and refer him to me if he does not get it. (We have met a few times; I was at Herb's house when Tri was there to learn how to build the tonearm. I last talked to him in person at RMAF last month.) The cost of shipping to and from Tri for you would probably be less than $25 round trip, if you use US Priority Mail. Chin up, old man! Hum due to bad, inadequate, or incorrect grounding is ALWAYS fix-able, and definitely does not indicate you have a defective sample. IOW, shit happens.

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.