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Hi Eric, I'll assume that your secondary was wound with brand new magnet wire and that it is a single layer with no overlapping turns. The behavior you are seeing is usually a symptom of overcoupling. This is a common problem for helical or inverse conical primaries, but it can also occur on pancake primaries. However, it can also occur if your coil is grossly out of tune. Based on the information you've provided, I suspect you indeed have a tuning problem. Your primary capacitor is relatively small and your primary has relatively few turns - the combination appears to be causing your primary circuit to resonate at a much higher frequency than your secondary's loaded frequency (with the 25" toroid attached). If the primary circuit is indeed driving the secondary at too high a frequency, your secondary will developing voltage peaks near the middle ofthe winding instead of at the top. This can easily cause sparkover between various regions of the secondary and result in little output at the top of the coil. Based on your coil's data, I estimate that your secondary should be resonant at about 230 kHz, but I really suspect you currently cannot tune the primary circuit down to this frequency even when you use all 10 turns on the primary. I'd recommend the following changes: Good luck and best regards, -- Bert --
: Hi everyone-
: i just built my second coil but its not working. I have a 4 inch
: secondary wound with 24 awg wire wound 22 inches tall. The primary is
: 10 turns of reallly thick wire and the capacitor bank are homemade
: bottle caps at 2.5 nanofarads. I also built a rotary spark gap. the
: torroid is 25 inches in diameter. Sparks are seen on the secondary
: skipping windings, and i cant get any spark off of the top of the coil-
: any suggestions???
: thanks
: eric
:
1. Quadruple the number of bottle caps to get up to 10 nF (0.01 uF).
2. Reduce the spacing of your main spark gap (or use a small static gap) to reduce the amount of bang energy until you can bring the system into tune.
3. Add a breakout point on the toroid so that you can see how long the streamers are.
4. Once you begin to get breakout off the point, carefully adjust the primary tap - carefully adjust primary tuning for longest streamers.
5. Once you are in tune, increase the spacing on the main gap (carefully - you DO have safety gaps on this system, don't you....) :^) Look for any signs of abnormal ("racing") sparking between secondary turns or between the secondary and primary.
6. Remove the breakout point and confirm that the system runs cleanly. If the toroid won't break out on its own, you'll need to reduce the minor diameter of the toroid or add a small breakout point on the toroid.
7. If you see sparking between regions of the secondary at full power, elevate it (relative to the primary) by 1/4" to decrease coupling and try again. If you never see any racing sparks, try lowering the secondary by 1/4" to increase coupling. Adjust coupling so that the secondary is 1/4" above the point where you see intermmittent racing sparks. Once you can run the system at full power without getting racing sparks, you're there.
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