Re: secondary questions

Subject:  Re: secondary questions
  Date:   Fri, 18 Apr 1997 06:54:41 -0700
  From:   "DR.RESONANCE" <DR.RESONANCE-at-next-wave-dot-net>
    To:   "Tesla List" <tesla-at-pupman-dot-com>

Hi Bert:

The main function of the polyurethane is to seal the coil from any
molecular level water adhesion/cohesion to the secondary coilform and/or
wire.  A better solution is to use Dolph's fast dry varnish (especially
formulated for HV work) -- known as Dolph's AC-43.  This will seal the
wires and cement them rock hard.  We usually sand the coilform first,
apply to layers of Dolph's, then wind the coil, and finish up with 5
thin layers of Dolph's allowing a full 24 hrs to dry between each
application.  The result is a bullet-proof secondary that is completely
unaffected by molecular water adhesion.

On high performance coils with sec. spark exceeding the sec. coil length
more than 25% we usually incorporate an acrylic disk inside the sec.
about 5 inches below the business end.  Seal in place with a healthy
of GE II silicon calking seal (clear -- never use the black -- curing


> > 
> > 1. why is the initial coat of urethane needed??? I can see that it may
> > help
> > adhesion of later coats, but unless the PVC is electrically conductive,
> > a
> > layer of urethane ontop of the PVC won't affect dialectric constants by
> > a
> > measurable amount, or so it would seem - yet the RQ files make a big
> > deal of
> > this.
> PVC absorbs water, and thus will become more conductive during humid
> days. The best approach is to dry the PVC by heating it - I used a
> couple of high intensity quartz halogen bulbs aimed at the coilform
> while rotating it. Once dry, it should be immediately coated with a
> couple of layers of polyurethane - the solvent-based stuff, NOT the
> water-based. Some coilere also coat the inside as well. A somewhat
> conductive coil form will add leakage current to your secondary, and
> will rob power from your coil. Even though I've sealed mine (on the
> outside at least), and added epoxied plexiglas end-plates, I still get
> somewhat reduced performance on humid days.