Re: VTTC provisional results

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

Original poster: "David Trimmell by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davidt-at-pond-dot-net>

Hi, I think you have done the easy part ;-) Looks like you have a good
coil to start on the Audio Mod part, runs cool (Very Important!), and get
prety darn decent discharge. How were you going to do the Audio mod, Screen
or Grid? I have never tried Screen mod, think it may be even more
difficult than grid. With grid you need to get your dc bias resistance up
prety high, so that may drop spark output somewhat, but the pulsing action
of the Audio will increase the spark also. Sugest filtering <100 Hz Audio
signal, as that seems to distort like something awfull. I have tried a
Audio output transformer from a old tube amp (15 watt), and that worked ok
with a 833 tube, aslong as I bypassed the DC component as sugested by
Dunkan. My setup:
 http://216.36.6.9/webdoc2.htg/Tube_coil/Audio/New_Audio1.jpg
But when I tried it with a 304TL it distorted to hell! In fact, the 304
seems not to like Audio Modulation much, it will work fine (low vol), but
is *very* sensitive, and allways wants to go into a nasty distortion. So I
can't say how easy it will be to find a good impedance match with your
tube to Audio transformer.

Great work Herwig, and keep these reports flowing!

David Trimmell

 On Wed, 21 Mar 2001, Tesla list wrote:

> Original poster: "Herwig Roscher by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>
> 
> 
> John Freau wrote:
> 
> > Can you just use the output across two legs of the 3 phase
> > transformer?
> 
> John,
> 
> The tranny has got 3 (of course!) windings, which are Wye 
> connected. Each winding offers 4.1 kVrms. If I used one of these 
> windings for half wave rectification, I would get 5.8 kVdc. Do you 
> mean this configuration? 
> 
> >  Even though, the power is less, the sparks may be longer 
> because of the single phase.
> - You are referring to AC operation do you? As the final goal is 
> audio modulation I need to stuck with DC.
> 
> >> Either you could use a 3 phase ballast at the primary side of 
> the transformer or a single ballast at the secondary side. But this 
> is HV....
> > I don't use any ballasting for a tube coil.  Are you refering to the
> > use of a spark gap TC?
> - Ballasting is essential with disruptive TCs of course. But I would 
> like to have a small ballast e.g. a loading inductance between the 
> rectifier and the loading capacitor in order to protect the stack of 
> diodes from being fried in case of a flashover. Been there, done that 
>  :-((  Up to now I am using a 10 Ohm/10 kV current limiting 
> resistor, which is 10" long.
> 
> Regards,
> 
> Herwig
> 
> 
> 
>