Unstable Tracking Force Conundrum- a ghost in the machine ?

So here’s a puzzle I’ve been unable to solve - maybe someone can shed some light?

A few days ago while using my Paradox Pulse Denon DL103-R I noted the bass was overly boomy and distorting on certain tracks - all other frequencies were fine. On checking the VTF it was 3.5g instead of the 2.5g I had set a couple of weeks prior. Putting it down to personal stupidity I reset to 2.5 and the bass was back to normal. Anyway, same thing happened again the following day- VTF measured 3.5g. Weird! To cut a long story short I reset and rechecked after an hour and it was again 3.5. I’ve repeated this on numerous occasions and the VTF drifts up by about 1g every time.

If I swap in either my AT 33PTG/II or Goldbug Brier the VTF stays stable - no drift.

I have recalibrated my digital balance and also used the Shure SFG 2 (very similar readings) in case the balance had gone off.

The TT shelf/TT/platter are all perfectly level.

The virtually new Jelco TK850s is correctly setup and arm/headshell set perpendicular using a spirit bubble and horizontal site rule.

The Paradox Pulse is in a new Jelco HS-30 with all fixings tight.

So I think I’ve eliminated all external factors and come to the conclusion it must be an issue with the cartridge suspension despite it being 2 years old and with only about 100 hours. It’s never been mishandled. I’ve discussed this with Terence at Paradox Pulse and he is adamant it can’t be the cartridge and even if it were broken it wouldn’t give these symptoms. He suggested gently depressing the cantilever with a finger - it did return to its default position on release and there was some resistance but I have no idea how it should feel. I can’t believe such a test can exclude a duff suspension.

I suggested sending it back to Terence for checking but he is sceptical and it’s also a long way to send it if it’s not the problem.

Anyway, long story but I’m out of ideas now. Grateful for any suggestions.

Steve



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The tracking downforce can't be altered by the cartridge, I'd assume the tonearm is responsible. Maybe the internal wiring is applying unwanted torque, although it would have to be pretty stiff wire to generate a 1g difference.

Steve
Have you tried the 103 in a different tonearm?
Charlie

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Originally Posted by walpurgis

The tracking downforce can't be altered by the cartridge, I'd assume the tonearm is responsible. Maybe the internal wiring is applying unwanted torque, although it would have to be pretty stiff wire to generate a 1g difference.

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If that were the case I’d expect to have the same problem with the other cartridges and they are both perfect. Totally stable. I even checked again this morning - after 24 hours the VTF on the Brier is exactly as I set it so I can’t fathom how it could be the tonearm unless it’s because the mass of cartridge and headshell (29g) is too much for the arm. I can get it to balance but the counterweight is virtually at the end of the arm. I did enquire from Hugo (Ammonite Acoustics) if there was a heavier counterweight available but apparently not.



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Originally Posted by topoxforddoc

Steve
Have you tried the 103 in a different tonearm?
Charlie

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I haven’t Charlie. The only other arm I have is an SME 3009 II with fixed headshell - there’s no way it would take the mass of the Paradox.

Walpurgis’s post has got me thinking that maybe this cartridge/headshell is to heavy for the arm with standard counterweight and the knife edge bearing is being “distorted”




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no kids who might have had a twiddle? suspension could be collapsing but im not so sure that would alter vtf much. something loose on arm

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Originally Posted by struth

no kids who might have had a twiddle? suspension could be collapsing but im not so sure that would alter vtf much. something loose on arm

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Nope defo no kids or vagrant twiddles.
Poltergeist?


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What TFGuage are you using , I had all sorts of problems with this type
https://www.ebay.co.uk/itm/0-5g-LED-...18d8413f0ae269

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Originally Posted by worrasf

Nope defo no kids or vagrant twiddles.
Poltergeist?


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duffer gauge?

no that wouldnt account for sound.. comes back to arm

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Originally Posted by struth

duffer gauge?

no that wouldnt account for sound.. comes back to arm

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Checked with both digital balance and Shure SFG 2