Turntable speed accuracy

Don,

You are simply wrong. Stylus drag will slow down any turntable, regardless of platter weight; it merely changes the period over which it occurs due to inertia. And yes, the 60Hz mains supply does fluctuate enough to be completely problematic.
Then again, if you can't hear it, more power to you.

If your platter is heavy, playing a record will not affect the speed.

That was the first quote from Don.

Needle drag does not slow down "Properly Designed" turntables!

That was the second quote from Don.
I guess I can agree with the second. it seems like a logical imperative :-)

I used to own a VPI TNT-V hot rod and a HRX.

EVERY time a pulled out the kab strobe the speed was different.

This had nothing to do with stylus drag.

Downunder,

Yup, that will irk you. Alas, that's a fine example of a poorly designed drive system; there's a reason the SDS was developed and that goes back to the AC mains. Trying to accurately derive 33.3 RPM using a crude phase shifting capacitor and hoping that the frequency of the incoming AC is stable enough to do the job is bad engineering. While frequency accuracy (and adjustablity) is one issue, it doesn't begin to address waveform shape, harmonic distortion, phase amplitude and shift, and all the other interesting things that go into generating a waveform suitable for driving a synchronous AC motor.

DC motors have their own set of problems...

Peter I forgot drive method. I have a Walker Ultimate motor controller plugged into an Exact Power 15 putting out a constant 120V, this combination keeps the speed as constant as I'm able to check.