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Re: Tube Coil

> Date:          Tue, 28 Jan 1997 23:16:16 -0700
> From:          Tesla List <tesla-at-poodle.pupman-dot-com>
> To:            Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject:       Re: Tube Coil
> Reply-to:      tesla-at-pupman-dot-com

> Subscriber: rhull-at-richmond.infi-dot-net Tue Jan 28 23:05:46 1997
> Date: Tue, 28 Jan 1997 18:52:49 -0500 (EST)
> From: richard hull <rhull-at-richmond.infi-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Tube Coil
> 
> At 10:26 PM 1/27/97 -0700, you wrote:
> >Subscriber: SSNSanders-at-aol-dot-com Mon Jan 27 22:09:29 1997
> >Date: Mon, 27 Jan 1997 15:41:26 -0500 (EST)
> >From: SSNSanders-at-aol-dot-com
> >To: Tesla-at-pupman-dot-com
> >Subject: Tube Coil
> >
> >Do I use RF chokes on the Sec. lines of the xformer on a tube coil. Do I
> >rectify the output and feed the system with DC or does the tube preform this
> >function. Is the pri/sec a normal Tesla setup driven by the tube arrangement.
> >Im thinking of using an 811-a in a "Hartly Oscillator" design. It appears
> >that the pri. in the tank is center tapped to ground. Im going to try a
> >microwave transformer, and buy a filament transformer depending on the
> >voltage of the 811-A , I think its 10v but Ill find out for sure.    Stephen
> >S.
> >
> >Stephen,
> 
> The 811 requires 6.3 volts on the filament try and get a beefy one so you
> can parallel tubes if so desired.  About 10 amps ought to do the trick.
> 
> Richard Hull, TCBOR


Stephen, Richard, All,

I'm now putting the finishing touches on a compact tabletop vac toob TC 
that uses four 811-A's in parallel running from a microwave oven 
xfmer.  I found room between the primary winding and the core on the 
microwave xfmer to squeeze exactly six turns of #14 AWG solid copper, 
PVC covered wire in there.  By winding it around the primary it is 
not subject to magnetic shunt current limiting like the HV winding.  I also made
a center tap at three turns for the DC path in the cathode circuit.  This puts out
almost exactly 6.3 volts to the bank of 811's and eliminates the requirement of a 
second filament transformer.  Only trouble is you cannot run a variac 
for variable plate supply power.  I will post more on this compact 
coil system soon.  BTW, it *really* puts out!  My secondary is 14 inches long 
and today I've achieved the full coil length in raging output brush fire. : )

rwstephens