How incorrect ARE the voltages?

If the plate voltage is 20% high for instance, measuring the DC level,
that means the AC voltage on that winding is 20% high too. And so you
need to remove 20% of the windings. So you do have a reference after all.

In the solid state world you can just assume the DC voltage after the
rectifier is 1.414 times the AC voltage, minus the diode drop. Problem
is that in the tube world there is often a substantial resistive loss
through the vacuum diode.

But, you can measure that! Measure the DC drop across the diode, then
work from the desired DC voltage, plus the drop, times 1.414 to get
the AC you need. (This is assuming the diode drop will change only a
little bit once you get the voltage perfect. If it's not, use the
nomograph in the RCA HB-3 handbook to work it out).
--scott

Hello Scott,

yes, the difference between the voltages measured on the (ill) re-wound
transformer and the original AC voltages (that I now precisely know) can be
useful to determine how many turns more or less are required for each winding.

That can be a useful information, as a potential problem is the fact that the
original transformer was designed for 60 Hz, and the turns, once calculated for
50 Hz operation on the same iron, may not fit the available space.

Anyway I should get that transformer within a few days, and I will then discuss
with the rewinder how to best proceed.

73

Tony I0JX