Vintage DD turntables. Are we living dangerously?

I forget the part number for the critical IC, but all I did was Google it, and I found many sources for it, in Asia.  Most are on Alibaba (I hope that's the correct name of that website).  I just chose a vendor who seemed to understand at least a little English.  The cost is cheap, once you find a vendor, because who else wants one, besides the few dozen people in the world who may be fixing TT101s?  Albeit, this was 3-4 years ago when I made my purchase.  One thing to keep in mind is that the chips are around the same age as the TT101, so I suppose it's possible that they can go bad just from sitting on the shelf under god knows what storage conditions, for 30 years.  One of mine was used to repair a TT101, and it worked, is all I know.

The QL-F6 has the same bi-directional servo as the 101. I have one of these and it’s very good. They are cheap on eBay.

" Although far less remembered than the QL-10 or QL-7, the QL-F6 has about the same motor structure as the former, the same specs as the latter - and, in spots, even surpasses both !
Bi-directional servo as in the QL-10 (and the TT-101 and TT-801), Coreless DC servomotor (as in the QL-10), continuously variable Q oil-damping for both horizontal and vertical planes, diecast aluminium cabinet, non-resonant "High-Density Pararesonance"
Bi-directional servo works with a push-pull amplifier in the drive circuit : two currents are generated in each motor drive coil, one pushing and one pulling the rotor.
The result is less overshoot in speed correction, 50% increase in efficiency, 40% increase in torque and the remedy to coreless' motors lower efficiency and lower torque capability... See the JVC TT-101 page for more details."

http://www.thevintageknob.org/jvc-QL-F6.html

Very interesting ... it is useful to look for some cheap model for spare parts.
A detail I do not understand about DDs is how the TT101 and the lower models use lightweight lightweight plates unlike the Technics SP or Kenwood L07D or other big turntables of the time.

First, take some of the stuff on Vintage Knob with a grain of salt; that site is not always perfectly accurate.  
Second, if you can find the IC as an NOS part, via Alibaba or other internet source, it will probably cost a few bucks each.  And you would be MUCH better off at a MUCH lower cost than trying to source the IC by buying a whole turntable.  You would have to pay the cost for a working unit, too.

As to platter mass, the SP10 Mk3 has the heaviest platter that I know about among Japanese vintage DD turntables, except possibly for the optional and very rare gunmetal platter for the Yamaha GT2000X.  But that latter platter will cost you about as much as a good GT2000, if you can ever find one.  (For the heck of it, I have been searching.) The L07D platter is substantial but only a fraction of the weight of the other two.  It can be enhanced by the addition of an optional peripheral ring specifically made by Kenwood for the L07D, which I own but don't use. The SP10 Mk2 platter is not much different in weight from that of the TT101 and the Denon DP80.  I don't know about the Luxman platter; there are a few owners on this thread who may tell us.  One determinant of platter mass back then may have been the choice of motor.  For a given physical size, coreless motors produce less torque than do iron core motors, but the correlation between coreless motors and platter mass is not linear, either, except to note that the Mk3 uses a gigantic iron core multi-pole motor.  The Pioneer Exclusive P3 has an impressive platter and uses a coreless motor, on the other hand. The GT2000 uses a coreless motor but had an optional oversize bearing and that optional massive platter to be driven by that same coreless motor.

The Yamaha GT2000 series turntables use the coreless motor supplied by JVC if I recall correctly...🤓