Re: coil questions

to: Stan, Terry

We use 1300 Ohm resistors rated 20 watts and they get only mildly warm.  If
they are getting really hot your coil is not properly tuned.  Usually this
is called by excessive overcoupling of the pri to sec coils.  Using a flat
spiral prevents overcoupling with small to med size coils.

If you are using higher resistance values such as 5K Ohms the power is I^2 *
R so the resistor will run hotter.  Usually only 100 to 500 Ohms are
required for "Q spoiling" which is what the resistors are doing, ie,
preventing oscillations in the power feed circuit.



-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Friday, July 23, 1999 10:03 PM
Subject: Re: coil questions

>Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>Hi Stan,
>At 11:07 PM 7/22/99 -0400, you wrote:
>>Terry, as always, thanks for the detailed reply.
>>I found the RC filter on your web site.  What wattage resistors would
>>you recommend for a 15/60 NST?  You said you used 250W but that it was
>>overkill.  Where can I find 30KV caps?  I tried Digikey and couldn't
>>find anything.  Also, what about a filter on the 120V side of the neon?
>I use 5k ohm 50 watt resistors.  Some people say they get really hot while
>I and others don't seem to have that problem???  they "should" work fine
>but realize that they normally can run about 300C.  They are basically like
>ceramic space heaters so plan on them getting really hot.
>The caps really only need to be 15kV each in retrospect.  I would just go
>the the MMC approach.  My new filter has five 1600 volt 10nF caps in series
>to give a 8000 volt 2nF cap (I run them over voltage :-)).  You could use
>10 1600V 10nF caps to get a 1000pF 16000 volt cap.  Dr. resonance also
>usually has high voltage door knob caps too.
>All the stuff about MMC primary caps can easily be applied to filter caps
>too.  Since the currents are very low you will always need only one string.
> Terry