Re: Over-coupled or under-insulated?

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

Original poster: "Harold Weiss by way of Terry Fritz <teslalist-at-qwest-dot-net>" <hweiss-at-new.rr-dot-com>

Hi Chris,

How many unused turns do you have on your primary?  On my 15", the primary
tuned at about 6 turns, but I still had racing.  The secondary was 3" above
the primary.  The unused 3 turns to the outside of the primary would arc
between turn 9 (end of pri) and turn 8.  I then made shorting jumpers and
shorted turns 9-7.  The coil then settled down and stopped racing, and
haven't had a problem since.  I know shorted turns around a TC are supposed
to be a bad thing, but in my case they seemed to help.  I think the
autotransformer action of the unused turns may have been causing the
problem.

May your streamers be long and plentiful.
David E Weiss



 > Original poster: "Chris Roberts by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>
 >
 >
 > Hi all,
 >
 > I have been running my 6 inch coil for about 2 weeks now with no problems
 > with the caps. (woo hoo!!) I guess we finally found the problem. However,
 > during fourth light, the secondary started sparking along itself. (yes, it
 > was tuned) I thought it was overcoupled and raised the secondary a bit.
 > Then higher, and higher... The bottom turn of the secondary now sits about
 > 5 inches above the primary, and the two innermost turns on the primary
were
 > cut out. (this leaves me with a 9.25 inner diameter) The secondary stopped
 > sparking for a while, but has started back up again. 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? Thanks.
 >
 >
 > -Chris
 >
 >
 >