Re: MMC vs. Maxwell caps?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Bill,

Tesla list wrote:

> Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<vanyo-at-echoes-dot-net>
>
> I'm building my first coil, somewhat medium size.
>
> The primary and secondary are done already (secondary is 6.5" by 27.5",
> 1000 turns of 22 awg, primary is 19.5 turns of 1/4" copper tubing, 1/2"
> spacing on centers, inside diameter 9.5").  Also have NST protection
> circuit complete (using plan from Terry).

One missing component is top terminal type and size. This will affect the
resonant frequency and
where you need to tune it at.Your primary at 19.5 turns and .03uF is around
66.6kHz. You'd need
a mighty toroid (much larger than you would allow a spark to emerge) to hit
that Fr. I like to
keep the toroid cord (roc size) slightly under or at least at the secondary
diameter. So say 6"
x 36" will put the secondary Fr at about 127kHz. The primary can then tune
at a near tap
position of 10.6 turns.

> I'm planning on using 2 or 3 15/60 NST's, and going LTR with a static
> gap, so I'll need 0.030uf or 0.045uf
>
> Now, I'm debating whether I should do an MMC, or try some of the Maxwell
> caps available here (near bottom of page):
>
> http://www.teslasystems-dot-com/products/index.html
>
> I know everybody loves MMC's, but these Maxwell caps appear more cost
> effective to me - a 0.03uf cap, rated 35kvdc, goes for $85.  I'd still
> be stuck with no cheap way to get 0.045uf - it would be cheaper to get
> 0.06uf (2 of these maxwell caps) and a 4th 15/60 NST, but 4 15/60 NST's
> might be enough to scare the neighbors (I'm stuck with running it
> outdoors - house has low ceilings).
>
> So, does anyone see any drawbacks to using these Maxwell caps?  Am I
> wrong about it being cheaper to use one of these for 0.03uf than to
> build an equivalent MMC?

The only real draw back I see is if the Maxwell blows, your out the cost of
the Maxwell. MMC's
have that advantage (replace the dead string should it blow). Thus, they
are more cost
effective. You could build a 0.03uF MMC for $81 plus a few dollars for
misc. materials using the
Geek Groups CD cap of 0.15uF at $2.25 each (3 strings, 12 caps per string,
0.0125uF per string
for 0.0375uF total = 36 caps total). This is the nice thing about using
higher capacitance caps
like the 0.15uF CD cap (the cost comes down). It actually comes down into
an area a larger
portion of the Tesla Coil community can actually afford to buy.

Take care,
Bart A.

>
>         Thanks,
>         Bill Vanyo