Debuzzing a Wheaton TriPlanar problem

thanks - I willcall. I assumed that no response to an email would mean no response by phone also. See my answer to Xiekitchen; his diagnosis may be right-on.

Hey -thank you - I can picture that scenario quite easily. But it happened with two different phono stages, and everything that can be grounded, is. I'm now suspecting a 'short' in the cartridge.

Thanks for your considered response. My former career was as systems software developer, and I appreciate your debugging skills. Occasionally (of course) there is feedback while the stylus is tracking the groove. My gut reaction suspects some sort of intermittent feedback. as you suggested, from the cartridge itself. It is an AudioQuest 7000 now some 15 years old and my new Masseto preamp deserves something better anyway. I'd hate to think it's the shielding on the Cardas cable touching the tube, because that would require a re-wiring but that's what my hands-on experience feels like. Cartridge replacement first, then rewiring. The multiple groundings were done to successfully eliminate a constant hum at table installation time.

ok - another piece of evidence to add, and this may be the most telling. When I grasp the finger rest at the end of the tube, the hum gets really loud. Just squeezing the tube itself ever so lightly stops the noise. And this part baffles me - all I can think of is a defect in the cartridge.

Now this is making more sense to me, and I thank you. The TT is 6 inches from the wall which conceals all the electrical lines from the apartment's circuit breaker. And I must ask what is 'screened tonearm wire' ? I want to try this fix before relocating the equipment rack. Thanks.

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.