Re: [TCML] Terry filter cap size

[Gary Lau <glau1024@xxxxxxxxx>]

Hi Jeff,

You don't need to alter the resistor value if you modify the cap
value.  The R-C filter has a frequency knee orders of magnitude higher
than the TC's resonant frequency, so changing the knee frequency
slightly is of no concern.  Just know that increasing the cap value
will result in more power to be burned off (lost) in the resistors, as
with each bang-cycle of the main gap, the filter caps are also
charged, and discharged into the resistors.

That your NST's are running 210mA means that the resistors will get
surprisingly hot, but they're made for that, so no concern.

The VERY important thing is that the number of MOV's is correctly
chosen for the NST voltage.  For a 9kV NST, you should be using 6 of
the prescribed MOV's on each side.  Using fewer will toast them, and
using more will render them ineffective.

Regards, Gary Lau
MA, USA


On Wed, Mar 21, 2012 at 3:53 PM, jeff mill <jeffmill2@xxxxxxxxxxx> wrote:
> Got another one
> I am using  nts’s 4ea for a total of 9000v @ 210ma
> I really, really want to protect my nts’s so I made and am using the standard Terry filter and pro gap. Instead of the caps they call for I am using 2ea  780pf ceramic murata door knob style, one in each have. These are all that I had. The filter calls for around 550pf. do I need to decrease the resistors from 1k to a lower value ?  Will this filter even handle 210ma plus.
>
> Thanks as always JM
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