When I first thought about this project I just built a mod section using parts from an old TR1998/STR9X a VHF Aircraft TX/RXThat was driving a TT15 Valve for output, as in this circuit.
That uses two EC90's as output and driven by a EL90. HT 250 Volts and -11 Volts on the grids of the EC90's
Unfortunately the transformer labelled 2T2 was open circuit, the wires had corroded, but the output transformer 2T3 with thicker wire was still OK.
I thought I could still use the idea driving the two EC90's with an ECC83 in a phase splitter circuit and an EF91 pre-amp, basically like the typical Mullard audio amp circuit, but there must be something particular with the transformer driver as I could not get the required swing.
This was my circuit.
I note once again that the November 1966 PW posted by Aub, again uses a driver transformer, so I am guessing that it must take the grids positive and as such drive the outputs harder sinking more current through the output transformer and bigger swings etc. I would appreciate knowing if that is correct.
Also I am quite happy if others post ideas, projects within this thread as I am finding lots of interesting comments on low HF transmitters, perhaps there could be other stations to talk to if enough get built, dug out of cupboards etc.
Perhaps change the main Title to something suitable such as Questions on 160/80m transmitters ?
Adrian