Phil wrote
"Creative Electronics uses a very "creative" approach to choke design
that works 99% of the time without measuring and pruning.
A 38 uh choke is installed in series with a 180 uh choke; the 180 uh
choke being on the power supply end of the HV circuit. A pair of
4700 pf @ 10 kv capacitors in parallel are installed at the junction
of the two chokes. The cold ends of the caps are pulled to ground
by a common open frame relay on 40-10 meters, and left floating
on 160 and 80 meters. Another
pair of
4700pf 10 kv caps are hard-wired at the base of the first (180 uh)
choke. This works well with their CE-2500A (3CX3000A7) and
other amps they build.
I have used this scheme several times...the chokes run cool and
do the intended job very well"
One caution: if the two 4700 pf caps which are hanging are not grounded by
the relay, they can store the entire plate voltage. The stored voltage
might not kill, but you would remember it. Therefore, a high value bleeder
resistor should be installed in parallel with the relay contacts to insure a
bleed off of the stored voltage.
73, Colin K7FM
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