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Re: 304TH vs 833A?



In a message dated 99-04-24 05:30:12 EDT, you write:

<< Original Poster: "Richard Staron" <rstaron-at-aracnet-dot-net> 
 
> Hello everyone.  Seeing all the notes flying around about using an 833A, I
> was able to find a tube in my
> junk box and had tried it out at Robert Stephens place last year.  However
> we found that the tube was
> soft and I put the idea of putting together a coil using that tube on the
> back burner until I was able to get another tube.
  
> I know have stumbled upon some other tubes and I was wondering whether the
> the 304H and 304TH could
> be used instead of the 833A?  If they could be used, does anyone have any
> schematics or design concepts on using this type of tube.  I would be
> getting these tubes and associated hardware in exchange for some other
> stuff in my junk box..............isn't it great being a bit of a pack rat 
:) !
  
> Looking foward to any replies
  
> Richard - VE3FAC
  
Richard,

Those tube should be fine.  I've used the 304TL which is basically
the same as the 304TH (different gain), in tube coils, and the set
up of the coil is very similar as the 833A set up.  Maybe a slight
difference in grid leak resistor and/or grid drive.  The voltage rating
is lower on the 304 tubes than the 833A though; 3kV, vs 4kV.  I've
never tried overvolting the 304 tubes.  I've gotten 10" sparks from
the 304TL, and David Trimmell has just reported longer sparks also
from a 304TL.  The 304 type tubes demand a lot of filament power;
5V at 25amps, or 10V at 12.5amps.  It can be wired either way,
because there are two filaments which can be connected in series
or parallel.  The plates on the 304's will tend to run toasty orange
though.  I'm not sure just how much toasting they can withstand.

John Freau