First Coil - No Sparks

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: First Coil - No Sparks
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 10 Jun 1998 20:17:59 -0500
Approved: tesla-at-stic-dot-net

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From:  Esondrmn-at-aol-dot-com [SMTP:Esondrmn-at-aol-dot-com]
Sent:  Wednesday, June 10, 1998 2:55 PM
To:  tesla-at-pupman-dot-com
Subject:  Re: First Coil - No Sparks

In a message dated 98-06-10 05:31:51 EDT, you write:

<< 
 I just completed my first coil yesterday but I'm not getting any discharge.
 
 4.3" x 21.625" secondary - 22awg - 10 coats laq before winding then 15 more
 coats.  Ground via 10' flat braided cable to 10' of #4 stranded to 8' ground
 rod.
 Started with slight overcouple.  Moved incrementally up to 1/4" above first
 primary turn (no affect).
 
 19"x4" toroid - Foil tape over foil over dryer duct and pizza pans.  Tried
 4" - 8" above final turn on secondary.
 
 1/4" copper tube primary, spaced 1/4" 15 turns total - tried tap at several
 spot on turns 14 and 15.  15 degree rise. Just over an inch between first
 turn and secondary.
 
 15kv 30ma NST
 
 NST protection -
     A 500ohm/65w resistor from each NST lead
     1000pf ceramic caps across resistors
     3.5mh coil on each leg (one coil showed "minor" shorting so I removed
 both from circuit without affect)
 
 Safety gap - across NST (actually more like two gaps, one from each leg to
 ground)
 I set gaps so they just barely didn't fire with NST alone.  During runs, gap
 would go off almost non-stop, I adjusted so that it didn't go off, no change
 on output, readjusted so it goes off intermittently (once every 2 or 3
 seconds)
 
 Main gap - RQ static 6"x9x2" (8 gaps total) tested at 7 gaps in use)
 
 Caps - 4 Oil filled poly each rated around 5300pf, 7500v, wired 2 pair in
 series then the 2 pair are paralleled.  Value tested at 5240pf on a decent
 LC digital meter.
 
 Power controlled by 10a variac.
 
 There appears to be a great voltage increase if intensity of safety gap
 discharge is a correct indicator.  Main spark gap is firing and appears to
 be doing what I expected.
 
 All settings have resulted in zero output.  I had hope to be ballpark close
 and adjust from there but apparently, I'm not even on the field yet.
 
 Thoughts?
 
 Thanks,
 
 dj >>

dj,

Sounds like a good project.  I calculated the unloaded resonant frequency of
your secondary to be 492 khz and 273 khz with the 19" x 4" toroid.  With a
.0052 mfd cap, it should tune somewhere between 13.5 and 14.5 turns on the
primary.

The ground connections are longer than you would like.  Can you shorten it up
some?  The braided cable is not good for ground connections.  You would be
better off with solid wire or 3" to 4" wide copper or aluminum flashing for
the whole length.

Have you tried putting a wire or some metal object on the toroid?  And still
no sparks?  If the spark gaps sound like they are firing properly, the
transformer is probably ok.  How do you have it hooked up?  The high voltage
feed lines should go to each side of the spark gap.  One side also connects to
the cap and the other side connects to the inside turn of the primary.  The
moveable tap lead goes from the primary to the other side of the cap.

You might try fewer gaps in the spark gap, also removing all the nst
protection items one at a time.

Good luck.

Ed Sonderman