Capacitor order & tuning

cc: tesla-at-grendel.objinc-dot-com


I ordered my commercial capacitor yesterday.  I decided to go with .025mfd
since it was only $5.00 more than the .020mfd.  Here's the specs:

Value:  .025 +-10%
Working voltage:  15,000V RMS AC
Application: Tesla coil tank circuit
Type:  Pulse discharge
Dielectric: polypropylene, oil filled
Size:  Approx. 3.5" x 14.0"
Orientation: Will be used horizontally (laying down)
Price:  $185.00
Condenser Products had the best price by far and they were very helpful in
answering my questions.

I have a question about tuning.  I should have a very high Q system.  If so,
I would expect the best tuning point to be very narrow.  When I try to tune
at low power for best spark, the tune doesn't seem to be very sharp.  I have
it tuned at 13.25 turns right now - but it seems to run as good at 13.0 or
13.5 turns.  I think you would call this mushy tune.  I did move the
component board (with filter caps, safety gap and RF chokes) back about 5.0
ft. from the primary.  Your recent post about the secondary ground got my
attention.  When I wound the secondary I left about 4 turns on each end to
allow for connections.  I think I cut one or two off on the bottom end but
I'm sure there is still at least two turns between the last close wound turn
and the ground lug.  Is this part of my problem?

BTW, I noticed the other night when running the coil with the lights off that
there is a strong blue corona surrounding the coil that gets increasingly
brilliant once the spark gap is running as power is increased but before
breakout occurs on the discharger.  You can tell there is a lot of power
there and it wants to go somewhere.

Ed Sonderman