Thanks for the last couple posts. I've restored a few electrostatic sets and hadn't encountered the problems you initial described and thought maybe I'd just been lucky
As for ceramic caps, I've picked up a few sets that had ceramic doorknob caps substituted for the horizontal coupling caps that seems to work OK.
It was the vertical where I figured the piezoelectric effect would cause some major linearity issues, but your results seem to indicate otherwise.
So it sounds like this set has a linearity control ? I wonder how ceramic caps might work in a set like VT-71 that lacks this adjustment ?