Re: Over-coupled or under-insulated?

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 >
 > Original poster: "Chris Roberts by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>

 > So I get a strong
 > feeling that this is not a problem of coupling. I was suspicious of the
 > tiny amounts of dust that is embedded in the polyurithane, (I now know not
 > to re-coat after letting the coil sit for a while) so I removed all of the
 > spray-on polyurithane with paint thinner, and am currently putting on
 > several coats of varathane. Do you think t! his will be enough to stop
 > those racing sparks? If this works, would you recommend that it would be
 > safe to lower the secondary back to its original spot?

There is no such a thing as "overcoupling" in a Tesla coil. They are
-always- overcoupled, in the sense used in doubly tuned filters.
When a spark punctures the secondary insulation, it leaves a weak
spot, that will easily spark again. I don't see any problem in recoating
the secondary without removing the old varnish. Just clean it before,
and maybe sand it a bit too.
With the weak spot insulation reinforced, you can lower the secondary
again and get more efficiency.

Antonio Carlos M. de Queiroz