[R-390] Power supply capacitors

[Tim Shoppa]

Don writes:
> Ken wrote:
>>Gord Hayward wrote:
>>
>>>IYou want the smallest capacitor that will give the minimum
>>>voltage for the regulator to work.  A bigger capacitor gives a 
>>>higher minimum voltage (less ripple) but the extra energy just shows up as
>>>heat in the regulator.  Bigger capacity also increases the inrush 
>
>>That's really interesting what you say Gord about the extra energy 
>>showing itself as heat in the regulator. That didn't even occur to 
>>me. My particular circuit uses a 2200uF and LM317 (among other 
>>things) to produce a stable and regulated 12.6 volts for the 
>>filaments of the BFO and PTO tubes and the regulator DOES run 
>>hot.
>Before everybody goes nuts putting smaller capacitors in their power 
>supplies, here is another view.  Don't forget that electronic voltage 
>regulators don't eliminate ripple, they just reduce it by the loop 
>gain of the regulator.  Reducing the ripple in the raw supply will 
>reduce the ripple in the regulated supply, and lower ripple is pretty 
>much always better.

Guys -
  Isn't this a bizarre amount of effort to remove ripple in a circuit
(BFO and PTO filament) that was originally 60Hz AC to begin
with?

  I realize there is a long and deep tradition of discussing
ballast tube replacements and am sorry if my observation
interferes with the tradition :-).

Tim.