.
>
> ## when playing with conventional choke input supplies, not the resonant
> types that
> henry radio used, you are in for an eye opener. When you 1st turn it on,
> you get this
> huge yo-yo oscillation on the P-P v waveform, that finally settles down.
> what psud wont
> simulate is a varying load, like ssb-cw. Once the supply is up and running,
> and no more
> soft start involved, is when the trbl starts up. Every time you hit the
> key, you are slamming this
> big load on it...and you end up toggling between full and no load. Every
> time you hit the key,
> that oscillation starts up, and P-P V is sky high, till it settles down. On
> cw, that’s next to impossible.
You have to use bleeder resistors so there is always a load on the
supply, or swinging choke on the input.
I suspect modern day amp manufacturers avoid using a two stage LC
filter because the iron costs more and adds weight. Nowadays even
good 330 uF electrolytics, a string of 8 let's say, is cheaper and
smaller. I think that once you start getting above 50 uF @ 3 KV the
stored energy gets high enough to IED on a fault. CW rigs used choke
input filters for years--actually the handbooks say you can get by
with more ripple with a CW rig--maybe it was okay because they were
class C? I'll find out eventually--I have a single 813 with a 1500 v.
supply from a pair 866As and dual LC filter to try out.
73
rob
K5UJ
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