[Amps] Filter Capacitors

[Rob Atkinson]

.
>
> ##  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