Around the mid 80's I first pioneered and prototyped this new circuit adding the additional capacitive input full wave higher B+ supply for existing modulators in my Viking Valliant. I used zero biased 811A's for modulators. This Economy Supply schematic has been copied world wide allowing greater B+ for the modulator tubes in many ham transmitters including Valiants, DX-100's, Viking 1 and 2, Rangers, etc. In most cases the maximum positive going modulation ability is severely limited by the existing turns ratio of the modulation transformer. To develop proper positive going modulation there are three choices available. Change the modulation transformer,  drop the RF final quiescent B+  or raise the modulator B+. In this case I raised the modulator B+ by adding only one additional large part a 20 MFD or slightly larger cap. Here on the Valiant I used a 20 MFD@ 1KV Oil cap, on other prototype rigs I sometimes used three 60-80 MFD @ 450 volt electrolytic caps in series\ with 100K voltage dividing resistors.  Preferred are mod tubes with plate caps. But many have used 6550, 6L6, EL34 and many other non plate cap variety with ceramic tube sockets. Little 6146's, 807's, 1625's tetrodes have no problem with the higher plate voltage.  811A triodes run nicely with zero bias in the Valiants, Vikings, DX-100 and Apache's. With tetrodes we used separate 1K resistors to each modulator screen grid  and 10 to 15 ohm cathode resistors to reduce distortion with the cathode resistors providing fusing to protect the modulation transformer. Please protect the High voltage and other power supply transformers  <<<here>>>.

    Later around the late 80's I used a 30 watt Dynaco HiFi audio output transformer in my DX-100 with LW6 Modulator tubes. If I owned a large Audio amplifier I could have feed its 4 ohm audio into the Dynaco low impedance secondary and not used the internal modulator tubes. Here I mount the new T1 on a Lexan bracket and apply modulator supply B+ through a 1 Meg ohm resistor to the transformer case to reduce Mod Xfmr dielectric breakdown voltage.

I strongly recommend adding  The ( so called ) 3 diode negative peak limiter   by Steve, WA1QIX    for Plate modulated Transmitters.