Re: Instrumental TC tuning

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

Original poster: Esondrmn-at-aol-dot-com 

In a message dated 10/28/03 11:53:49 AM Pacific Standard Time, 
tesla-at-pupman-dot-com writes:


>Hi everyone
>
>Since installing a new secondary to my coil, problems have been
>occuring.  I think my caps were having problems due to a poor connection
>between my ground and the secondary coil.  However, with the grounding
>connection cured, my safety gaps are firing constantly.  I have tuned as
>well as I can by maximising spark length.  I have reset my safety gaps
>to fire at 105% and my main gap is always firing (although I am going to
>measure the breakdown voltage).
>
>I want to tune using measurements and am checking that I've got it
>right.
>
>Have a 50 ohm impedence scope and will use a 100k resistor in series.
>For secondary resonance I disconnect the ground from the secondary and
>connect the resistor to the ground in series with my generator (what
>voltage and waveform should I use) I will place my scope across the
>ground of the generator to the base of the secondary.  I alter the
>frequency and look for a drop in output.
>
>For primary resonance.  I disconnect my filter and bridge the spark gap.
>I connect the function generator with the 1k resistor in series to the
>tapping point on the primary and with the scope between the function
>generator ground and the tapping point I measure the voltage looking for
>a voltage rise.  I set the generator to the resonant frequency of the
>secondary and move the tapping point.  Can I alter the tapping point
>with everything running?
>
>Any other areas to look at for why my safeties are going constantly?  My
>topload is small, I am running at near resonant capacitor and my ground
>could benefit from some attention, BUT, it was all OK when I had my old
>secondary.
>
>Cheers, Chris. (NZ).


Chris,

If your safety gaps are continuously firing with the coil in operation and 
they don't fire when connected only to the high voltage transformer, then 
you are experiencing 60 hz resonance in the primary circuit allowing the 
primary voltage to go way above what would be normally expected.  Proper 
setting of your main (static I expect) gap will fix this.  For a 15 kv neon 
sign transformer, I use .20" to .25" maximum.  Increasing your primary 
capacitance value by about 50% will also help.

Ed Sonderman