RE: Problems with First Tesla Coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dave Hartwick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>

Dan,
Others with greater knowledge will probably reply, but I'll take a shot.

Do you know the Fr of your secondary and topload combo? Can't go anywhere
till that is known. I'm thinking you should be using a 6" (at least)
secondary and large toroid for a tank circuit with a 13 turn primary and
0.0275 ufd cap.
That tank will probably Fr in the 120 kHZ and up range, unless you have a
small primary and are intending to use a 4 inch sec. Still--0.0275 is a
larger value with respect to coil applications.

I always try to pre-tune by measuring Fr of the sec and tank with a scope
and sig generator. This will get you very close if done correctly, after
which you should be seeing at least some break out.
Dave Hartwick

Hello,

I am having some problems with my first conventional tesla coil.  I've been
trying to tune the thing all night, but no success.  Only a few blown MMC
capacitors.  Here are my specifications:


15kV/60mA NST
Synchronous Rotary Spark Gap 120BPS  (with safety gap)
.0275uF, 28kV MMC (LTR type)
13 Turn Primary

Here are my questions - hope their not too many . . .

1.  From my calculations, if I was using a 0.0106uF capacitor, my primary
wouldn't be able to tune this as it calculates to about the 15 turn. (Mine
is only 13 turns)  However, if I make this calculation
with my LTR capacitor (.0275uF), then the primary should be tapped
approximately 7-8 turns.  Does this sound right, or when using a LTR sized
cap with a SRSG do I need to do something else in my calculations???

2.  I've never tuned a tesla coil before.  Tonite I was just going around to
every turn, inching up my variac to about 25%, and monitoring current or
hoping to see a little streamer or something.  But nothing.  For a typical
primary this size, how much tapping range is there to actually have the
think work a little.  Is it very narrow, or if i'm within a half a turn i'll
get some output???

3.  When I actually do hit resonance, at what percentage output voltage
should i expect to see some type of streamers begin???

4.  Can the quality of the RF ground be the difference between output and no
output???  I know some people on this list claim to get output even when the
RF ground is left floating??

5.  Anything else that i might be missing???  The SRSG is running fine and
sounds like its properly running.  It is synchronized with the 60Hz and
tuned correctly.

Tomorrow I will use a smaller toroid to see if I indeed have a primary with
too few turns.

Thanks for all the help.  I'm about scratching my head right now.

Dan