Posted by sideliner (A) on March 12, 2017 at 21:50:16

In Reply to: RE: TFA-204 300B Operating Points posted by jdrouin on March 10, 2017 at 12:39:17

3K is not the series resistance of the primary. 3K is the OPT's primary AC impedance. What you need to input, is the transformer's primary DCR which you can just measure with a DVM. That value should be anywhere from 150 to 300 Ohms as is typical for most transformers. If the primary's DCR is say 200 Ohms, there will be a drop across it of: 200R x 0.06A = 12V. You will be going from 250V down to 238V at the tube's plate.

Edits: 03/12/17