[TCML] the REAL first light

[mark olson <kc5gym@xxxxxxx>]

Thanks to everyone who has responded so far.

I checked each capacitor that did not blow, 22 of them, with a meter that 
has .1 mfd resolution.  I found two that
were not .5 mfd, but 1.0 mfd.  These were misrepresented when I purchased 
them.  I had two spares, one was a
.5 and one was a 1.0.  I installed them, 21 @ .5 and 3 @ 1.0 for a total of 
.022 mfd.

> Each string is then 0.063uF and when three strings are placed in parallel, 
> the total cap bank capacitance is 0.188uF
> and it's rated only at 12kVp. Not only is the cap bank standoff voltage a 
> whopping low 12kV, but the cap value is off by one magnitude. Also, the 
> initial description of your cap failures sound like voltage punch through 
> which for me further supports an MMC configuration blunder.

Bart,

The caps are in series.  I only had enough resistors to bleed three caps at 
a time.


> Yes, BUT..............  I've lost the original note but if I recall 
correctly Marko is using a 12 kV, 30 ma transformer >which would have a 
leakage reactance of the order of  400 k.  The reactance of the 0.188 ufd 
capacitor would be only >about 14 k so can't see much of a resonant rise.

Ed,

The transformer is a 15 kv, 120 ma.

marko wrote:
Can this test be done as simply as using a 120v to 18v transformer wired 
"reversed" for about 800v?
How are the results interpreted?"
Ed answered:
>If you mean connect the 18 volt winding to 120 volts the answer will be 
instant smoke!!!  The transformer core will >saturate and draw very high 
currents, either blowing a breaker or burning up the winding.

A current limiting resistor in series with the 18v winding and 120 v should 
work, right?
My question was how would one interpret the current reading when testing 
capacitors as Dr. Resonance suggested.

I provided a safety gap across the NST.

I rolled the repaired coil out of the shop and connected it up, remembering 
the primary tap this time, and turned up the
volts. It was daylight outside so corona was not visible, but I could see 
some disturbance in the air surrounding
topload.  I got visible 20" streamers to a rod in the ground. The safety 
gap fired at 60 volts on the variac.  I adjusted
the safety gap, and re-fired. Still too close. Re-adjusted. Had to "loosen" 
the coupling.

I was able to get 40" streamers before another cap blew. I was at 80 volts 
on the variac.
The coil works!!!  HOORAY!!  my very first coil.

Apparently I must come up with another capacitor design.
Also, I have run out of primary and it is apparent that I need more 
turns... I'm thinking about adding an inductor to the
tank, but if I must re-do the cap, maybe going up a bit in value would 
eliminate the nneed for an additional inductor?

As you guys can tell, I still need help.

Thank you very much,

Marko  (Yippeee! it works!)




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