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Slow Building Streamers
Original poster: "Harold Weiss by way of Terry Fritz <teslalist-at-qwest-dot-net>" <hweiss-at-new.rr-dot-com>
Have any of you had a coil that would slowly build up streamer length on
My 15" coil, with no variac, just an on/off switch, would start with short
6" streamers and build up the length over about 15-30 sec, to 3.5-4'. Specs
Form: 15" OD 5/8" wall PVC sewer 40" length
Turns: 545 #14 155 Nythane mag wire
Winding length: 36 5/8"
Sec AGL: 25" (above ground level)
Torrid: 20 X 5" spun Al
Hight above sec: 2 1/4"
Fres: approx 120Khz (wire length calc)
Pri ckt: series (gap accross xfmr)
Cap: 5 X .010 uF 100 KVDC (Fair Radio)
Gap: series, 3 gaps, 1/2" carrige bolt shafts with rounded
and polished tips, 3/8-1/2" total gap
Discharge path wire: dual #14 15KV GTO stranded wire
Other HV wiring: #14 15KV GTO
XFMR: dual 15/60 NST
NST filter: RCR, 1.3K 53W ww, 250pF (Ceramite),
1.3K 53W ww
PRI: flat spiral
PRI supports: acyrlic (bronze smoked)
PRI OD: 30 1/4"
PRI ID: 19 1/2"
PRI turns: 9
Conductor: 3/8" Cu tubing
PRI-SEC spacing: 2 1/4"
SEC above PRI: 1 1/4"
RF ground: power ground
Base construction: Plywood/2x2, glue and pegged,
no screws, casters and xfmrs
While tunning this coil, I had arcing between turn 9 (end of pri) and turn
8, with tap set at turn 6. I had racing sparks also. To stop the arcing, I
shorted turns 7-9 together, which resulted in the elimination of the
racing. I noticed that the racing would only occur while 8 and 9
arced. When the two wern't arcing, no racing. The ideal tunning point
seems to be at 5 7/8 turns, although I made my tap lead too short to hit
it. ( I can hit 5 6/8 and 6, and can hit the outside in all sectors but
that one. ) I also found I had 15A breakers in the garage, which cut run
time about 10 sec. The sound of the spark gap echoing off the neighbors
house, sounded like someone firing a .22LR machine gun. It had the cadence
of an M-60D firing at 650-700 rounds per minute. ( ex-Army helo
crewchief) Max streamer length about 2 1/2'.
Once I got this coil to the theatre, I had a 20A breaker and isolated power
ground. The stage added another 3 1/2' of hight above the reinforced
concrete floor. The power distro had GFCI outlets at 20A. I had a number
of GFCI trips with both the coil and Jacob's ladders I was using. Every so
often, the coil would trip the breaker before it would fire the gap. I
think one of the NSTs has a intermittant short in the primary. Luckily it
hit every show cue perfectly for that wonderful simultanious gasp of the
audience. In the still air of the theatre, streamers could grow to 3
1/2-4'. This is where I noticed the slow streamer growth. The torrid was
too small, giving lots of breakouts that grew in length, almost like I had
a variac, and was ramping up the power slowly over about 15-30sec. The
only difference was the sound of the gap remained the same throughout this
time. Gap temps after 1min were warm but not uncomfortable to touch.
Any ideas on what's causing this?
David E Weiss