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First Coil - No Sparks
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From: Gary Lau 10-Jun-1998 0812 [SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: Wednesday, June 10, 1998 7:37 AM
To: tesla-at-pupman-dot-com
Subject: Re. First Coil - No Sparks
Hi DJ:
I think your problem is in your NST protection network:
>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)
The problem is the way you have your bypass caps wired. Rather than being
across the resistors, they should be from your NST terminals to ground (in
parallel with your safety gaps), forming a low pass filter with the resistors
and chokes. It's no wonder your safety gaps were firing, and it's lucky that
this didn't fry the NST. Other than that, everything about your system looks
good.
Regards, Gary Lau
Waltham, MA USA
>From: djQuecke [SMTP:djQuecke-at-worldnet.att-dot-net]
>Subject: First Coil - No Sparks
>
>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