Re: Tank setup with neon xfmr

Subject:         Re: Tank setup with neon xfmr
       Date:     Fri, 18 Apr 1997 06:35:52 -0700
       From:     Bert Hickman <bert.hickman-at-aquila-dot-com>
Organization:    Stoneridge Engineering
         To:     Tesla List <tesla-at-pupman-dot-com>

Tesla List wrote:
> Subject:  Tank setup with neon xfmr
>   Date:   Thu, 17 Apr 1997 16:15:32 -0600
>   From:   "Ben Hofmann" <bhofmann-at-ix-dot-netcom-dot-com>
>     To:   tesla-at-pupman-dot-com
> Hi Folks,
> Been browsing through messages on the list for a few weeks now.  I'm
> a newbie to Tesla coils in a sense.  I have played around with them
> in the past with very little success, but I think it was due to lack
> of, and poor information resources.  This mailing list, as well as
> the FTP site has helped me to understand a lot.
> My question is:
> I have read before that when using a neon transformer to power a
> tesla coil, since the xfmr's secondary in grounded in the center, the
> CENTER of the primary for your coil also needs to be grounded, and
> tap the primary on either end with the HV lines.  Is this correct, to
> ground the CENTER of the primary of your coil?

NO. The primary is usually "tapped" in some manner to permit tuning
adjustments, but there's really no need to try grounding any part of the
Tesla Coil primary, even if you could find the inductive center-point
(which would NOT be the same as the physical centerpoint, BTW).  

> I have read and browsed the information in rqdocs.zip on the FTP
> site, and could not find an answer to this.
> I also remember that the tank circuit should have two capacitors in
> series with the primary (one on either side), and the gap across the
> power supply end of the caps.  Is this correct.

Not essential. Richard Quick was very big on symmetry. The advantage of
using two caps in series is that the voltage stress is shared. However,
in the "equidrive circuit", the caps need to be very closely matched,
AND you need to always remember to "bleed" off any residual charge
build-up from circuit imbalances before attempting to work on the coil.
A single cap system, with one HV cap in series with one leg of the
primary does not have these restrictions/concerns. 

To be on the safe side, you should always remember to discharge the
primary cap, even in this configuration, since it could retain a charge
IF you accidently openned up your neon's secondary circuit.
Performance-wise, it's not clear that the two configurations perform any
differently. I seem to remember RQ claiming a 10-15% perfomance
improvement when he went to the "equidrive" configuration. However, I've
also seen many very high performing systems using the single leg
capacitor configuration.

> I would appreciate any input.  I have been itching to put together a
> coil, but my current status (college student living in the dorm) is a
> hindrance.

Well, summer's a comin' (although in Chicago, it looks like we're going
to skip Spring and do a flash-cut from Winter to Summer! Robert keeps
sending us down that cool Canadian air!) :^)

> Thanks.
> -Ben Hofmann
> bhofmann-at-ix-dot-netcom-dot-com

Safe [future] coilin' to you, Ben!

-- Bert --