Re: [TCML] the REAL first light

[Ed Phillips <evp@xxxxxxxxxxx>]

mark olson wrote:

> Thanks to everyone who has responded so far.
>
> A current limiting resistor in series with the 18v winding and 120 v 
> should work, right?

   Yes but you wouldn't get much more than perhaps 140 volts out of the 
120 volt winding.

> 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.

   Mistake.  The safety gap should be set with full primary voltage and 
NOTHING ELSE CONNECTED TO THE TRANSFORMER and left that way.  Period.   
If you open it any wider you can "overvolt" the transformer.When you've 
done that you can hook hook up the primary circuit and main spark gap 
and capacitor and go ahead and tune.  I think we all agree it's best to 
have the main spark gap across the transformer, in order to minimize the 
RF voltage the transformer sees.

> 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.

   Congratulations!  See above about the safety gap.  Get it set and 
THEN play with primary circuit tuning and coupling adjustments and you 
probably won't have further troubles.  On the other hand, it's not clear 
from your description of your capacitors whether they're really low loss 
and if they're not they may blow because of overheating.

> 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?

   More capacitance would be a better way to go but either will work.

> As you guys can tell, I still need help.
>
> Thank you very much,
>
> Marko  (Yippeee! it works!)

Ed

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