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
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