Re: still not working

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Danny,

Since the spark gap is firing "fiercly" you must be pretty close!

Usually, the problem new coilers have is that the primary circuit and the
secondary circuit are not tuned to the same frequency.  You don't give
quite enough information here to calculate what those frequencies are.

You give:

Secondary diameter 6.5 inches
Secondary length 24 inches
Two MOTs for 5000V
7 primary turns 2 inches apart
Primary cap 0.12mfd*
No top terminal

*I don't see how you get 0.12mfd from 24 (8 x 3) 0.015 caps?  If you put
three 0.015 caps in a string of three then the string will be 0.005.
Multiply that by eight and I get 0.040 mfd...  Are your sure 0.12 is correct?

So here's what you need to do:
Tell us the following additional information:

What gauge wire is on the secondary or how many turns are there.  That will
allow the calculation of the secondary inductance.  If you don't know,
count the number of turns in one inch and then multiply that by 24 inches.

What is the inner and outer diameter of the primary.  We need to know the
inner and outer dimensions and the distance between turns or similar
information to calculate the inductance of the primary.

Check the primary cap value again to be sure it is 0.12mfd.

Get a top load (and tell us the dimensions too :-))  Just wrap aluminum
foil around a basket ball or something.  You really do need some type of
terminal or your coil will be much harder to tune.

What type of spark gap do you have?

Do you have a variac on your coil? 

With this information, we can find the frequencies of the primary and
secondary circuit and tell you where to tap the primary to tune it (or
pretty close).  If this is not the problem, we can go deeper but usually
this is the problem.

It sounds like you are 95% of the way there.  We just need to get past some
small problem and it will work great!

Be super carful of the MOTs!  They are far beyond deadly!

Cheers,

	Terry



At 06:05 PM 7/26/00 -0400, you wrote:
>i am kinda new at the tesla coil game.  i have built a 6.5 inch diam coil 
>that i was planning on powering with 2 mot's  (5000v togther)that i had lying 
>around.  the coil specs are 6.5"diam  24 inch tall (secondary)   7 turns of 
>copper tubing for the primary 2 " apart.  i have constructed a .12mfd 19.5kv 
>mmc made from 24 smaller .015mfd 6.5kv caps  (8 strings, 3 caps per string).  
>when i hook it all up the spark gap fires fiercly and the mot's hum loudly 
>but the coil never fires.  i know the capacitors are working because i 
>charged and discharged them a few times.  i have the bottom side of my 
>secondary grounded to a metal bar that is pounded into the ground.  my coil 
>has no torrid because i haven't had time to make one yet.  is there anything 
>that you experienced guys can see that i am doing wrong??   any help would be 
>greatly appreciated    thanks a bunch   -danny 
>