Re: First VTTC light, and a few questions

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 7/20/00 5:02:35 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "Grayson B Dietrich" <electrofire-at-juno-dot-com> 
>  
>  Ralph,
>  
>  upon further thinking about this advice, I realize there is something I
>  ought to mention. I'm not using a a center-tapped filament transformer.
>  Also, as this is the cathode, wouldn't one expect there to be RF present
>  in it? I think that an RF bypass cap would be better used on the wires to
>  the meter.
>  
>  -Grayson Dietrich

Grayson,

Yes, it might be possible that the RF is simply affecting the meter
reading, but not really raising the voltage on the filament.  If the
filament voltage is really increasing, then it should get visibly
brighter as the voltage rises.  I don't use center tapped filament
transformers either.  I do use a bypass cap from the ungrounded
side of the filament to ground.  I used to use a clamp-on ammeter
and it read 50% higher when it was physically near the TC.

Are the output sparks long and straight, or kind of fuzzy, just
curious.  I often obtain the longest sparks when they are straight
and sword-like.  This is affected by tuning and other adjustments,
as well as by the Q of the secondary it seems.  Are your 811A's
new or used?  If used, they may have low emission and don't 
have enough emission to ever get red.  If you can increase your
input voltage from the plate transformer, this would help to redden
them if they have sufficient emission.  Did you try running off a
140V output type variac?  I've never used 811A's myself, so I'm 
not all that familiar with their capabilities or behavior.

Assuming you have good tube emission, another way to increase
the plate current is to reduce the number of turns in the primary
and use a larger cap to tune.  Higher voltage operation is more
efficient though.

Cheers,
John Freau