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Primary Resonant Rise

Hi everybody,
              I've recently been helping Stan Harle with some coil
problems, one of which involved this. He was having trouble with
erratic (static) gap firing and it was a problem that I've experienced
with the advent of buying and using my first neon transformer (I've
been using another type up to now). We identified a parasitic 
resonance caused by the transformer limiting inductance and the 
primary capacitor as the cause. I did some experiments last night to
quantify the effects and found some horrors - some of which I know
others must also have come across.
    Firstly, it turns out that the current limiting is almost 
exclusively inductive - the resistance of my transformer secondary 
(12kV -at- 60mA) is about 5kOhms end to end. So I experimented with 
some different values of capacitors. Firstly, I hooked my new 10nF
cap across the secondary, connected the o'scope across it, then fed
the primary from my lo-Z signal generator (it turned out that the
high-Z of the transformer made it virtually impossible to couple
a signal directly into the secondary without altering the transformer
characteristics, even with high value resistors). I noted a resonance
on the scope at approx 70Hz (NB the capacitor reactance at 50Hz is
considerably higher than that of the transformer at 50Hz). I then
measured the Q of the circuit. It turned out to be about 5.8!!!
It took around 80 Ohms of resistance in series with the primary to
almost totally kill this effect. It goes without saying what a waste
of power this would involve if hooked to the mains. The poor power
factor of the transformer would just make this worse as well.
     With a capacitor roughly matching the impedance of the 
transformer at 50Hz, the resonance shifted down to 50Hz (not 
surprisingly) but still had a massive Q.
     The upshot is that this parasitic circuit is capable of 
generating voltages far in excess of what the transformer is designed
for. It would seem that with a static gap across the transformer
as normal (and NO CHOKES) things should be O.K. as long as the gap
is not opened beyond the o/c voltage of the transformer. A rotary
gap might be a real problem if this condition is present as there
are times when it cannot limit this resonant voltage.
     Question - do people kill the Q of this inductance, and if so 
how?  If I wanted to use a capacitor other than the value which 
matches transformer impedance at mains-f it would seem that the Q 
must be killed in order to prevent frequency beating between the 
mains and the parasitic oscillation.

    I would greatly appreciate people's comments on and answers to 
this.

Malcolm