Re: Over-coupled or under-insulated?

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

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 3/13/03 9:03:12 PM Pacific Standard Time, 
tesla-at-pupman-dot-com writes:


>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


Chris,

Where are the racing sparks?  Bottom, middle or top of secondary?  With 
your 9.25" primary I.D. and the bottom turn of the secondary sitting just 
at the top plane of the primary, the coupling should be fine.  This is a 
flat primary, yes?  How about describing your toroid - size, shape and 
distance above the top winding of the secondary.  Since I don't recall, 
what is the power supply?  Spark gap?  Primary capacitor?  Are you 
absolutely sure it is tuned correctly?  Have you ran the math to calculate 
about where the best tap point should be?

Ed Sonderman