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Instrumental TC tuning



Original poster: "Mudford, Chris" <chris.mudford-at-agresearch.co.nz> 

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).
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