[Amps] Power factor and choke vs resonant-choke input supplies

[Peter Chadwick]

My understanding of the choke input supply is that within limits, the larger the choke, the better the regulation for any given bleed current, because the current through the choke is more constant as the load varies.. The reason for using an almost, but not quite, resonant choke is that it artificially looks like a very much bigger inductance, so a smaller bleeder is needed. If it is resonant, then some very high voltages appear across the choke, since the twice supply frequency waveform is in series with a very high impedance, so one would expect the voltage regulation to suffer.
Having adopted this approach, I find it works extremely well. For a LV supply, such as for screens, negative lead filetring and a rectifier on the filter gives a cheap negative bias supply....

>FYI PLASTICON CAPS have zero tolerance for over voltage.<
Not like the old papers! One of my first rigs used a WW2 8 uF paper cap rated at 500 v. I paid the equivalent of 5c for it, and it ran for some 18months at 900 volts before going short circuit. For tuning chokes, I have some WW2 papers from radars: they're rated at 5kV and a 0.1uF is about 5 inches high, 1 inch thick and 1-1/2 inches wide. One heavily insulated terminal on a big white ceramic insulator, and one terminal on a phenolic insulator, which is why I use negative lead filtering.
73
Peter G3RZP