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An attic find. Thorens Td160. Dusty and dirty. It's been a couple of years ago since I last worked on it. The motor spindle has a wobble. It was noisy off and on. I gave it a few drops of oil. With the belt in place and with the outer platter on it's quiet now. There's still oil in the main bearing, will refresh it tomorrow.
There's a little play in the arm bearing but not alarming. The arm seems to move freely.
I mounted an Ortofon Super OM body with an OM10 stylus. At 1.6 gram VTF the Ortofon "oscillates", it jumps up and down constantly while playing normal records with music. No lateral movement, just up and down. I exchanged the OM10 stylus for an OM20. Same result.
I have an Orton Super OM20 cartridge also in a Sony 2250 DD TT. No "nervousness" whatsoever.
I'm scratching the back of my head. Is the sprung subchassis oscillating? The arm/cartridge mismatch? Any ideas?
"The torture never stops"Greetings Freek.
Follow Ups:
You've excited the vertical resonance of the stylus suspension so the first guess is arm mass mismatch. However, it could also be related to the subchassis or motor/platter interactions causing micro vibrations in the platter at the "right" frequency which would also excite the vertical resonance. The arm mass is probably the main reason why you get such a profound bounce in either case. You need a lower compliance stylus like an Arkiv (9um/mN) in the OM body to confirm.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Is any indication of it's condition, there is nothing wrong with the cartridge/stylus. Joking aside...
My friend had that arm / stylus combo looong time ago and can not remember any issues with it.
VTF is likely not correct, how did you set it up. And if the arm does not move laterally when it jumps neither is ASF.
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"One must be sane to think clearly, but one can think deeply and be quite insane."
take a blob of modeling clay of about 1gr or place a 1 gr weight on top of the headshell (for s shortcut, use blue tac or equivalent to anchor it) and see if that stops the oscillation. if so, the compliance of the cantilever suspension is a mismatch for the mass of the tonearm.
i got the "grado dance" with a grado fte+1 on my grace 707 and quelled the prob with the modeling clay. i just left it that way until i swapped the cartridge.
all this, of course, is assuming rebalance and resetting of the VTF to prevent too much pressure in the groove/stylus interface.
...regards...tr
The mass of the arm is 16.5 grams. The compliance of the cartridge is 25x10. The weight of the cartridge is 5 grams. The resonance frequency is 7 hz. According to the calculation chart on vinyl engine,it is in the warp region. That just might be the problem!
Checked the anti-skate?
You're thinking of the OM3E and 5E. The OM10 has always been a nominal value of 1.5±0.25g.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
anti skate it NOT the problem. To me it sounds like the arm/cartridge combo is wrong.... I had an Ortofon that was unstable....sent it to Ortofon, and they fixed it. I'm not saying that's your problem, just a thought.
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