Vintage DD turntables. Are we living dangerously?

Halcro, do you have the patent number?  The TT-101 service manual describes the bi-directional servo as the differences between a simple F/V servo which has to coast to slow down, and a PLL which is bi-directional in this sense, and is something every 'table with a PLL (aka Quartz Locked) has.  

Dear @halcro : Fortunatelly the JVC chasis is very similar to my Denons and I mounted both in the custom plinths of both Denons with the same tonearm. Maybe you are rigth and I am " simple unable to hear discriminately..".

You need to grow-up in your knowledge and ignorance levels. I don't know what happens with you because I think that in this same thread ( if not in other where you posted too. ) I posted that that " touted " bi-directional servo in the JVC and that for you is the " penultimate wonder " on TT was a unique in JVC designs when was and not is  ( I don't know where you try to learn or with what kind of audio advisors you are surrounded. ) that way because not only what jp posted but Denon stated about that bi-directional servo in its DP-70M and latter on the DP70L models.

I assume that you think that discovered the " black thread " with the JVC. Wrong, nothing special. It's one units in the  japanese TTs bunch and that's all. Obviously that when some one ignore audio information can makes a misunderstanding in this and other audio subjects.

So, what are you talking about?

Better than that please do it a favor let it go the JVC in change for the new Technics units.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Perhaps this is what Halcro is referring to: https://patents.google.com/patent/US4888564A/en?q=phase&q=lock+loop&oq=phase+lock+loop. From a brief glance, it looks like what is described in the tt101's service manual. Perhaps it is related to the pitch control capabilities that the tt101 and tt81 possess and their other turntables, e.g. tt 71, don't. I leave it to those with superior technical minds to render judgment.

For those who prefer their information concatenated with pretty pictures, Vinyl Engine has several jvc brochures from the late 70's which describe the merits of their line of quartz turntables (along with the 'numbers' for each turntable in a convenient side by side format).

One other tidbit relating to the differences between the tt101 and the tt 81/71 is this: only the 101 has a coreless motor. If one is to praise Technics for utilizing this type of motor in their new design (they are terribly late to the game, no?), then one should acknowledge at the very least that the 101 should sound different, and likely better, than its siblings. To dismiss the 101 after listening only to its siblings therefore strikes me as a logical error.

Jp,
Hopefully you can make sense out of what Banquo managed to find...?

I can only add that all of Victor's other turntables have PLL controlled motors but only a few (TT-81 and TT-101) include 'bi-directional servo-control' in their descriptions.

If what you say is true about all PLL servos....why do you think this would be?

The Jvc Victor has patented this many years after the ceased production of the TT-101 81 and TT801 what sense does this have if it will probably not produce more important or top-level turntables?