Vintage DD turntables. Are we living dangerously?

Hiho
I think that the greyness is produced, amongst other things, by errors in the speed sensing mechanism. These are due to the way they are put together which can be corrected. I don't think that "pulse" is the correct term for this phenomenon.
IMO the technics TTs get into trouble because they have so much correction torque available. They can respond faster than most TTs to error signals. Even if these error signals themselves are erroneous.
My treatment method is applicable to any DD TT.

The term " jittery" you use is spot on and is what I use to describe the effect on my krebsupgrade web site.
Once heard it cannot be unheard!

Previously when the 'STOP' button was pressed...the platter instantly stopped due to the reverse current in the drive circuit....and then reverse spun for a second before stopping. This reverse spin was due to my removal of the stock heavy rubber platter mat which I have substituted with the lightweight Victor pigskin.

As you might already know, Halcro, the force of the reverse current can be calibrated via adjustment of variable resistors in the circuitry. My tech told me that the adjustment would be a PITA to do because he would need to build something to lift the turntable up a couple feet so he can put his test probes underneath while the table is running. I guess if one wants a perfect table, it might be worth doing. But of course the calibration is tied to a specific weight mat; change the mat and one would need to recalibrate. I left well alone.

In this discussion of those horrible SP10 Mk2 and Mk3 turntables, let me point out, as I did to Richard privately, that there is a world of difference between Mk2 and Mk3. I think I can say that with some authority, as I have owned both, in similar plinths, serving as signal source for the same system in my home. The Mk3 is worlds better in the area of grayness or "irritation" compared to the Mk2. I could and can happily live with my un-modified Mk3, and I do not hear the problems I associated with the Mk2. With the Mk3, one has a very energetic sound that could be accused of erring on the "clinical" side, whereas I definitely did hear the gray-ish coloration with the Mk2. That said, I am a believer in the Krebs mods; I've just got to get the cash together. Every Mk3 owner who has had the Krebs work done is ecstatic, so far as I can determine. (Do you think I should sell a turntable, maybe?)

Richard, Did you refer to the Technics motors as AC synchronous types? Since the PS puts out pure DC, I assumed they were DC motors.

Lew.

Yes the SP10s are DC motors. Maybe the confusion arose when I said that they are 3 phase. The supply voltage does not swing across zero.

cheers.

Interesting story HiHo......
I agree with you about the sound of violins on a DD.
Perhaps even more so than the piano.....the holding and modulation of a single string when bowed, can reveal the truth about accurate and consistent speed control of a turntable. More than with any strobe or even the Timeline.....with a solo violin there is nowhere a mediocre turntable can hide and if you haven't heard one on a great DD.....you may not even realise it?

It does seem odd though to cram all the added circuitry of the 101 just for the sake of the readout. And to expect people to pay nearly $1k more for it in 1977.

This is a quote from the DirectDrive Website....

At the end of the 70s the japanese audio-industry was in a unique position. They had gained control over the worldwide audio-market, the Yen was cheap and big numbers of well-educated engineers brought one innovation after the other out of their laboratories. The "golden age" of audio had risen - those were exciting times with many new models being developed and announced in regular intervals. At the end of the 70s there really was a sort of race between the mayor-players introducing ever bigger, better and more sophisticated turntables sometimes at very high prices. To understand this you have to know that the Compact-Disc at that time was close before introducing, almost every audiophile had a turntable already so the mid-class market was set. Apart from these reasons the analog flagships of that time were image- and prestige-products of the japanese companies often subzidized by their mass-market brothers.
Machines like the Sony PS-X9, the Trio/Kenwood L07D, the Technics SP-10MkII or the Denon DP-100 were built in a "cost-no-object" attitude that never again arises out of Japan. The best materials, excellent Build-quality, oversizing of all parts and innovative ideas were the characteristical ingredients of the top-decks at that time.
Those machines marked the end of an evolutionary process with non-measurable Wow & Flutter or noise-specifications and they had a sonic quality that even by nowadays standards is state-of-the-art. But 1982 the CD finally arrived and it was the beginning of the end for those machines. All japanese companies concentrated their engineering efforts towards "digital". Production-costs had risen and the Yen was standing higher making export of audio-gear more expensive. This was the time when the cost-cutters arrived and soon dominated the engineers. The analog-battleships developed in the late 70s and early 80s were the first products that were killed by this new ideology. Like Dinosaurs they had become bigger and bigger and now they're end had come.

As you might already know, Halcro, the force of the reverse current can be calibrated via adjustment of variable resistors in the circuitry.

I didn't know this Banquo...so thanks :-)