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Hi Jim, Welcome to the hobby - the smell of ozone is addictive, isn't it... :^) Lack of performance can be cause by a number of factors. My first suggestion is to reduce the size of your MMC capacitor from its present value to about half the value if you're using a 9 kV/60 MA NST, or about 1/4 the present value if you have a 60 kV/30 MA NST. The present MMC may be too large for your current NST. Instead, use 9 strings in parallel (for a 60 MA NST) or 5 strings for a 30 MA NST for your MMC. You'll also need to retune the primary (by moving the tap to outwards) in order to get the system back into tune. My second suggestion is to use a fan or blower to keep the spark gap electrodes cool or, better yet, convert to a spark gap that has more electrodes so that you have more small gaps (using inexpensive copper pipe segments as electrodes). This will improve "quenching" which keeps more energy in the secondary so that you can get longer sparks. Stay away from any rotary gap (at least for now). Some other things to verify or try: Make sure your toroid is relatively smooth - if you are getting multiple sparks instead of single streamers, the toroid may have rough or projecting points. Multiple simultaneous sparks prevent you from forming nice long streamers. Also, did you use the aluminum foil type corrigated dryer duct? Cheaper aluminized Mylar ducting tends to work very poorly, since it has projecting wrinkles that generate corona and multiple sparks. Finally, once you've tuned the coil for longest spark, try lowering the secondary (or raising the primary) to increase coupling? Do this in 1/4" increments until you begin to get racing sparks (sparks that begin to go from the top portion of the secondary winding to lower portions or even the base of the secondary winding). Once you get these, excessive corona between the primary and secondary, or sparks jumping between the secondary and innermost primary turn, reduce the coupling. You may need to do these adjustments in a darkenned room so that you can see any misbehavior. If, after trying these changes you still have problems, let me know and we'll take a deeper look at your system. Good luck and play safely! -- Bert --
--Previous Message--
: I am new at coiling. Just completed my first coil. I a question concerning
: the length of the streamers. My secondary is 4" inner diameter and
: about 20" long. I am using a 9kV NST and I built a MMC. The MMC
: consists of 190 capacitors rated at 16kVDC .068 microfarads. I have 10 in
: series and 19 parallel. My primary is 50' 1/4" copper tubing spaced
: 1/4" apart. I have a single spark gap and the toroid is made of
: 4" ducting. I am getting many streamers, but they are only about
: 8" long. I believe that I could achieve longer streamers, and my
: question is of course......how. I am thinking possibly get a 15kv NST and
: a larger torroid along with tuning it, but I would like the opinion of a
: professional.
: Thanks
: Jim
:
Did you use polypropylene capacitors for your MMC? If you accidentally used Mylar caps, they'll be quite lossy and will dramatically reduce coil performance. Also, Make sure you've adjusted the primary tap for longest spark. An out of tune coil will perform poorly and can damage your NST or MMC.
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