Jelco sa 750e

I read that if the vtf was hard to turn it would need to be cleaned and regreased

Did you have your cleaned and regressed?

I did, but only on my 66fx and only because the side panel fell off on arrival.
Look at the VTF spring of my 66fx with new grease.

My NOS samples of the 64fx are all fine, two of them. I also have 64fx PRO and it’s also fine. As you might know the fx series was made in the '80s and overall quality of some parts are better than old 64s from the early '70s.

The armlift and arm base are better on FX, dynamic tracking force is always in better condition that on 64s.
So the problem you are talking about is a common problem for 64s , but not for FX series.

I learned this from a guru, and it turned out to be correct. Sometimes the FR64S and probably the 66S, so maybe the 64fx, pivot can feel kind of "stiff" at first. This may also apply to the VTF adjustment. The guru advised to just put the tonearm under a heat lamp for a short while, to cure the problem(s). I did this with my 64S, which did come to me with a feeling of viscosity in the pivot and a very stiff VTF adjuster. The heat lamp cured the viscous feeling in the pivot bearing entirely, and the VTF adjuster got looser, but the latter is still a bit stiff. I think you want it that way, so the chosen setting does not vary during use of the tonearm.  Despite the fact that I am using my 64S in my basement system, where the ambient temperature is typically in the mid to high 60s, cool by US home standards, the bearing has remained free after that one heat treatment.

Interesting, I know very little about the fidelity research arms

except they are heavy mass and great for low compliance catridges

heat lamp warms up the grease I guess?

FR 64s and long 66s are heavy mass toneams made of stainless steel.

64fx and long 66fx are NOT heavy mass tonearms, they are made of aluminum and copper. 64fx with optional counterweight (W250) can handle superheavy carts like SPU and FR-7fz, but with stock small counterwight the 64fx is perfect for nearly all MM and MC cartridges (old or new). Those two tonearms are predecessors of the IKEDA tonearms available today (same PS distance BTW). You can read about IKEDA here.

heat lamp warms up the grease I guess?

  If there is a problem (*typically with 64s) you can try this method, but I think you’d better open/clean to add the new grease, it’s very easy! Before you buy, ask the seller about the condition, if there is a problem - don’t buy such a sample and find another. My 64s does not have such a problem.  

I see, thanks for the advice and clarification