[Amps] AC or DC better for indirectly heated cathodes?

[Radio WC6W]

On Wed, 19 Nov 2003 13:09:00 -0000 "A.J Moss"
<linear.amplifier at ntlworld.com> writes:

  <snip>
> 
>     If I were to make a floating adjustable regulated DC supply, I 
> could use an ordinary pot to control the heater volts, meter it, and 
> have a fine adjustment to within ca. 1V either way to set optimum 
> heater volts. I could also then add a current limiting option on the 
> regulator to limit inrush at switch-on
> 
>     Are there benefits, advantages, or just risks of using such a 
> scheme? Constant unvarying power at the heaters seems good, but is 
> 'less' 'more' to use the cliche.
> 
> 73 and thanks for any input
> 
> Adam
> 

Hi Adam,
   I wouldn't build the supply from scratch but...  there are lots of
inexpensive surplus regulated switching supplies available that do a fine
job in that application.   The better units come with inrush limiting,
plus crowbar circuits in case the supply goes crazy.

   I've used both AC (tapped from before the rectifiers) & DC on the
heater with excellent results.  

73 & Good afternoon,
   Marv  WC6W







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