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Re: Help...I'm having a lot of problems here...



Hello K & K,

Notes below.

----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Help...I'm having a lot of problems here...
> Date: Monday, February 15, 1999 7:28 PM
> 
> Original Poster: "Kent & Kim Schaffer" <santoken-at-bright-dot-net> 
> 
> Hello all...
> 
> About six months ago my step son and I decided to build a TC for his
science
> fair project.  Boy, was that a mistake...

Don't agree.  Sounds like a great Father and Son project, which can
continue beyond the science fair!
> 
> First I'll tell you that this is my first coil project, so I'm sure we've
> made a lot of mistakes in our design.  I think that one of my biggest
> mistakes is that cap we are using (I thought I would try to save some
time
> and money).  

Agree - see below.
> 
> Power source:
> 
>     Furnace transformer or NST (I'm not sure):
>             -10KVA
>             -25 milliamp
> 
> Cap (set back for a good laugh):
> 
>             -12x    2KVDC .01 uf ceramic caps soldered  in parallel for a
> total of 24KVDC
>                 -submerged in mineral oil in plexi box
> 
This is the main problem.  No doubt, you meant you soldered your caps in
series.  By so doing, you ended up with a capacitance of about 0.00083 mfd
which is much too low.


> Spark gap (another joke):
> 
>             -plexi box with three adjustable gaps in series
> 
> Primary:
> 
>             -3/8" copper tubing
>             -ID 7.7"
>             -Wire spacing ..875"
>             -5.5 total turns
>             -wound flat (0 degrees)
> 
> Secondary:
> 
>             -4.2" diameter (thin wall PVC drain pipe)
>             -21" long winding
>             -22 ga wire - enamel coated
>             -shellaced before and after winding
> 
> Toroid:
> 
>             -4" dryer duct
>             -12" diameter center of tube to center of tube
> 
With your secondary and torroid, and the 0.00083 mfd cap you made, your
primary tuned circuit is tuned to a frequency much higher than your
secondary frequency (which is around 300 kHz.)

> Now here is the problems we're having:
> 
> After hooking up the cap the way all the schematics show I get no
discharge
> at the spark gap at all.  BTW, the way I read the schematics, one
terminal
> of the cap attaches to the output of the transformer and the other
attaches
> to the ground.  Now, if I attach the cap in a series (one terminal input,
> the other output) I get spark at the gap.
> 

I hate to say it, but there is a possibility that you have blown your caps,
and that some or all of them are shorted.  24 KV DC is marginal.  Try an
ohm meter set to read megohms and measure each individual capacitor.  Each
one should read infinite resistance if they are still good.  

It is hard to determine how you hooked up your circuit.  The gap should be
connected across your transformer.  The cap and primary should be in
series, then connected across your gap and transformer.  


> I have gotten absolutely no discharge at the torid whatsoever...sure does
> light a flourescent tube nicely though :-)
> 
> Does anyone have a suggestions...I'm sure some of you must!  Your
response
> is greatly appreciated, since the science fair judging in Thursday...Yes,
> this Thursday.
> 
> Kent

With time so short, drastic measures are needed!  Assuming you can't
improve your capacitor (which should be about 0.025 mfd for your current
primary), then I believe your only hope is to increase your primary turns
to about 32 turns to achieve proper tuning of the primary to the secondary.
 You will probably have to abandon the copper tubing and go with #10 or #12
house wire, spaced about 1/8 inch turn to turn.  Or, you can use insulated
house wire and just close-wind it.  Tuning will be somewhere around 28-30
turns - you will have to experiment.

Your torroid is a bit big for the power you are feeding your coil.  You
will probably have to tape a thumbtack or other pointed object on it to get
some breakout.  If you make the torroid smaller, say 3" by 6", you can
reduce the number of primary turns needed by several turns.  
 
Good luck.  Keep working on it till you get it working.  This list can
help.    

--Steve