Tony,

I did exactly what you are describing. I used a solid state audio amp,
and drove a tube type audio output transformer backwards to step up the
impedance from 8 ohms to several thousand ohms. I used a 4 uf oil capacitor
to couple that across a HV choke that carried the RF final amp plate
current. For a choke I used a 125 watt Stancor poly-pedance modulation
transformer where I used as much winding on the primary as available. It
worked very well.

It might be easier to consider cathode modulation, and in this case the
transformer turns ratio will be much less, and the HV problem will also be
less. Maybe a 110/220 vac to 12vac 5 amp filament transformer will work out
here. This is just a guess, but it might work. Cathode modulation is a
combination of plate and grid 1 modulation, so the % eff is somewhere
between 66% (plate) down to 33% (grid) , and might end up at about 50%.
Consider the 220 vct winding where the grid return goes to the CT, and the
cathode goes to the top of the 220 v winding, and the bottom of the winding
goes to ground. Your turns ratio need may vary, but the concept proposed is
workable.

Jim
WD5JKO


"Tony Angerame" wrote in message
...
I've acquired a high power 50 watts plus tube type hifi output
transformer. I'd like to try modulating a pair of 6146's with a hifi amp.
The circuits I see use a modulating inductor in series with the B+ to the
final to keep single ended dc off the transformer secondary.

Here's the rub. Where do you find a 30-50 henry inductor for 800+ volts?
I was thinking of checking out the secondary of a tv transformer? (Not
many left used to be common whatever happened to those tv's).

Anyone have any ideas on winding one? Seems to me taking an old
transformer apart and scramble winding as much wire as one can afford
might do the trick?

Ideas?


Thanks,


Tony,

WA6LZH