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Re: [TCML] Re-visited - Newbie question - Where does all the energy go?



Hi Peter,

...trying to add my 2cents, beginning at the start, and in 3 areas:

1.) NST
An experience of my Friend Fritz Egli:
NST Transformer F.A.R.T, nominal 230V --> 7kV/50mA, center tapped.
Ball safety gap, total 6.4mm (2 x 3.2mm ,  Center on Mains ground).
Working at first, drawing 2.8A at 245V primary mains voltage,
but after short time only drawing 2.1A, and getting warm.
Then no more able to fire the safety gap; this one had to be
reduced to total about 50% of former distance. But it fired on BOTH
HV-side gaps! My guess: not a shorted turn in the secondaries,
but in the PRIMARY. A replacement of the NST by an 8kV/50mA of
a different brand, solved the problem.

Sense of the long story: even if having both of the secondary halfcoils
firing, you can have a shorted turn in the primary, which makes the NST
a doorstopper :-(

2.) Capacitor
There was not so much talk in this thread, about the cap. I fully respect
if someone is building his own HV caps. But I don't fully trust the results
of such effoirts (see i.e. my own story with the PCB-cap at:
http://home.datacomm.ch/k.schraner/pcb_cap.htm )

You wrote before:
The capacitors are homemade, three liquid paraffin filled tubes of
approximately 60 nF each in series giving 18.1 nF in total.
and: - I made various new capacitors, same result.

Question: did you also try to go the MMC route, with the notorious
Cornell Dubilier 942C20S1K-F caps, seen here:
http://www.cde.com/catalogs/942C.pdf

The idea behind: a good cap can make a huge difference in performance!

3.) The Spark Gap
...as others have commented, can make a big difference in performance!
In your situation, I'd observe 2 things, at first, without going to new constructions:

a) ...regarding quenching: do the tubes fire, nicely distributed along the tube axis, or are the firings concentrated in a narrow zone. If so, the widh of the gaps
along their axis, might not be adjusted precisely enough, or there might be
irregularities in the copper (i.e. a seam), and there would be bad quenching.

b) I'd try to narrow the total gap width from your 5mm to say 3 or 4mm, by tapping less of the tubes (say only i.e. 4 to max 6 of your eight tubes), and see what happens.

Hope, some of it is useful...

Regards, Kurt
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