Re: TC Part alternates

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "robert & june heidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-desertgate-dot-com>

Michael: your research is correct to a point. The physical voltage tolerance
of a resistor depends on the distance between the ends of the wires in the
construction and the case insulation value.1/2 watt and larger resistors
have about 1/4' distance and a thick insulation layer on the outside. Carbon
film resistore have about the same distance between the end caps but only a
coat of paint on the outside as insulation so they tolerate less voltage by
surface conduction. The 1/2 watt resistor will hold the test, but the margin
is close in voltage and power. A 1 watt composition resistor gives a better
margin of safety. Two 1/2 watt resistors soldered with their wires soldered
side by side (not wrapped) do even better. 10Meg is a good value of
resistor. I use 33 Meg, but they are hard to find and discharge slower than
some people like. No resistor is perfect so you must use due caution in all
cases. The glass case high voltage resistors can cost over $10 each Vs.
$0.20 for composition so most of us compromise and live with some risk.
   Robert  H
-- 


 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > Date: Thu, 19 Dec 2002 18:11:43 -0700
 > To: tesla-at-pupman-dot-com
 > Subject: RE: TC Part alternates
 > Resent-From: tesla-at-pupman-dot-com
 > Resent-Date: Thu, 19 Dec 2002 18:16:49 -0700
 >
 > Original poster: "Michael Quarles by way of Terry Fritz 
<twftesla-at-qwest-dot-net>"
 > <mquarles-at-qusion-dot-com>
 >
 > Since I obviously don't have a modicum of understanding of electrical
 > theory, can you tell me the voltage rating requirement for the bleeder
 > resistors?  I, being limited in my understanding, would think you would need
 > resistors that can handle 2000v.  However on this board I see experienced
 > people recommending 1/2 watt carbon film resistors that have about 350v max
 > working voltage.
 >
 > Others say no you need a 2000v resistor and they recommend metal glaze
 > resistors.
 >
 > In my searching the metal glaze resistors have a higher voltage but nothing
 > near 2000v.  I have found thick film resistors that will handle 2000v but
 > they are rather pricey.
 >
 > Thanks for your help.  I learn more each day.
 >
 >
 >
 >> -----Original Message-----
 >> From: Tesla list [mailto:tesla-at-pupman-dot-com]
 >> Sent: Thursday, December 19, 2002 7:44 AM
 >> To: tesla-at-pupman-dot-com
 >> Subject: Re: TC Part alternates
 >>
 >>
 >> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
 >> <Mddeming-at-aol-dot-com>
 >>
 >> In a message dated 12/18/02 7:09:49 PM Eastern Standard Time,
 >> tesla-at-pupman-dot-com writes:
 >>
 >>
 >>> Allelectronics has the caps but the closest resistor I could
 >> find there is:
 >>> 400 ohm/50 watt ceramic
 >>> I could put 3 in an series to get 1200 ohms but what happens to
 >> the watts?
 >>
 >>
 >> Your composite resistor will be able to dissipate 150 Watts.
 >>
 >>> I also read I should use 10M ohm 1/4 watt 2000 volt bleed
 >> resistors for the
 >>> Geek Group caps, but isn't the 1/4 watt a problem?
 >>> Isn't there a lot more than 1/4 of a watt going through them?
 >>
 >> The power supplied TO the SYSTEM is not the power being
 >> dissipated
 >> (used up) BY each RESISTOR. The power being dissipated by the resistor is
 >> E^2/R, where R is the resistance and E is the voltage drop across each
 >> resistor.For say, 2000V drop across each cap, a pair of these in series
 >> would each dissipate 1000^2/ (10^7 )=0.1 watts. Now 2000v across a single
 >> 10M resistor  would dissipate 0.4 watts, in which case a 1/2 watt
 >> resistor
 >> would be a better choice.
 >> This points out why some modicum of understanding of electrical
 >> theory is preferred before completing a coil.
 >>
 >> Matt D.
 >>
 >>
 >>
 >
 >