Vintage DD turntables. Are we living dangerously?

Another thing: I decided to check out the motor bearing on my own. There is a large screw at the bottom of the motor (visible by dropping the sheet metal cover on the bottom. It is sealed with some kind of hardened clay like material. I carefully scraped and vacuumed away the sealant and then I opened the screw... lo and behold I saw a small steel bearing and it was sitting in about 1/2 ounce of oil!! Dirty oil at that. The screw itself is a cup and at the bottom of the cup is a plastic thrust plate.
I cleaned out the old oil with a soft cloth and let it drip out - but nothing really did, and re-filled it with Mobil 1 motor oil. I didn't re-seal it as I will get back in there in a year or so and do it again and the screw/cup holds all the oil it needs.

I wanted to be sure the spindle/motor spun smoothly once I had it all back together. But, I heard a rubbing sound when I turned the spindle (platter off). Oh crap. I had torn apart turntables before so I thought - here we go again.

There are six screws around the motor on top - three hold the motor in place and three hold the black steel top plate of the motor in place. I took all six out (they were surprisingly tight) and lifted the plate off - no more rubbing sound. I spun and listened as I reassembled it and if I over tightened any of the screws the rubbing returned. Once back together, rub free, I put the platter back on, hooked it all up and voila! It spins free and long without any sounds. I don't know if the tech tightened things up or what happened but I am thankful that it was such a simple fix.
It is playing Oscar Peterson in Russia right now and Peterson's flying fingers sound ever so beautiful.

Lew,
I think the Victor TT-101 originally sold for 165,000 Yen whereas the TT-81 sold for 75,000 Yen?
Big difference but the complexity of all the variable 'pitch' options plus the dual bi-directional servo sensors all contribute as well as the motor difference.

Great thread - I concur that the TT101 is a great table and I had the same concerns as Halcro, so I have a back up for spares

I have a tech here in Ottawa who is from Vietnam and specializes in servicing vintage Japanese gear, his workshop is floor to ceiling with vintage "junk". He seems to be able to fix anything I have thrown at him, including by backup 101 when it started to behave badly. So I am on the page that we can get by for a few more years yet.

On another note, I bought a heavy lead plinth for the TT101 from Tommy Cheung specially drilled for the table and accommodates 2 arms. Makes a big difference, but admittedly I have not tried the table nude. I found the best mats are the micro seiki cu-180 closely followed by the SAEC SS300.
My reference table is my Seiki sx8000 and the 101 is very close, such that sometimes I muse on selling the big micro.

My observation on coreless motors in direct drive turntables is that there are physical traits, at least the ones I owned and saw in pictures. Please keep in mind that I am not an motor engineer so my observation does not define what a coreless motor is.

(1) The most obvious is that the rotor magnet is always above the stator coils and there's small gap between magnet and coils. (Less "grip" on the coils and, not surprisingly, less torque.)

(2) The series of coils on the stator are ironless. (Helps to simplify its construction)

(3) Lower torque than typical core motor. (Not as dynamic sounding or less "jump" factor.)

(4) Many, not all, rotate smoothly even without the platter so they do not rely on the inertia of the platter mass like other DD motor. (This is an indication of its fluid sound.)

Here are some examples and observe the physical similarities.

JVC TT-101

Sony PS-X7

Sansui XRQ7

JVC QL-A2

Kenwood L-07D

Kenwood L-07D

Pioneer PL-50L II

Sony PS-X6

Kenwood KD770D

Dual 701

Brinkmann Bardo

Halco: "Doesn't it seem odd....if a coreless DC motor produces no cogging and sounds so 'fluid', relaxed and unfazed.....that a manufacturer would be foolish to even contemplate an alternative design?"

Coreless motors were utilized in most later models of many brands, especially in the late 70's and early 80's. Pioneer shifted to coreless motors in almost all their later models. Kenwood did the same starting with KD-770D and KD-990 -- I don't believe the KD-500, a model in the early years, uses a coreless motor. Sony used their version of the coreless motor called BSL (Brush & Slot Less) quite early in all their "PS-X" series. With the exception of Technics and Denon, almost all Japanese manufacturers shifted to using coreless motors in the late 70s and ealy 80's. Denon stubbornly stuck to their AC induction motor all the way through the 70s and 80s.

The earliest use of coreless in DD table is not even in Japan but in Germany. Dual used the earliest motors in the 701 in 1973, few years before the use of quartz lock drive. The motor model is EDS-1000.

Back to Halco's question. Many Japanese manufacturers did ask that question and they decided on the coreless motor. If given another decade to further develop motor in DD technology, I believe almost all would use coreless motor, given the trajectory of the trend in Japan. But CD ruined all of that. :(

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Hiho, The information I have been able to gather suggests that it is simply more difficult to get torque out of a coreless motor than out of a similarly sized cored motor because the coreless motors tend to trap heat and thus overheat, and overheating is lethal to them. (The iron or steel core in a cored motor also makes a good heat sink, so motors intended for heavy duty and continuous operation tend not to be coreless.) However, the Pioneer Exclusive P3 (coreless) motor is second only to the Technics SP10 Mk3 motor in terms of torque among the TOTL Japanese DD's, as far as I can find out. (Perhaps the Denon DP100 motor develops more torque than that of the P3; don't know. It's as big as a coffee can, so I would not be surprised.) If you read about Kenwood's thinking in the design of the L07D, they actually did not favor high torque in principle. So they were not concerned with competing in that "horsepower" race. Also, the drive system (the implementation of the servo mechanism, use of a quartz reference, handling of the AC and/or DC, speed of the sensor mechanisms, etc) are also determinants of the success of a DD design; cored motors can be made to work just fine, IMO. The fact that Denon and Technics stuck with cored motors does not necessarily mean they were "stubborn". However, like you, I am not a motor engineer. Motors and how they work, what makes one better than another for this or that application, are fascinating and complex subjects.

Apropos of that, you cite the Brinkmann Bardo for using a coreless motor, and I did too in one of my earlier posts, but does anyone know about the Grand Prix Monaco, the NVS, or the Teres Certus? For that matter, what about the Brinnkmann Oasis?