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Re: Big Tiode

Subject:  Re: Big Tiode
  Date:   Sun, 18 May 1997 09:11:44 -0500
  From:   "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
    To:   Tesla List <tesla-at-pupman-dot-com>


> Date:          Tue, 13 May 1997 09:40:12 -0500
> To:            tesla-at-poodle.pupman-dot-com
> Subject:       Big Tiode
> From:          Tesla List <tesla-at-pupman-dot-com>

> Subject:  Big Tiode
>   Date:   Mon, 12 May 1997 09:44:52 +1000
>   From:   Ralph Down <rjdown-at-fan-dot-net.au>
>     To:   tesla-at-pupman-dot-com
> 
> 
> Hi All,
> I went to a local Hamfest last weekend and scored a large triode tube
> (valve).  It is a Philips TB 4/1250
> about 4 1/2" diameter and 6" tall with a very substantial anode.  I have
> tried searching on the web for info on this tube, but so far no luck.
> Does anyone have any data on this tube? - anode voltage, heater voltage,
> wattage, pin out etc?
> I hope to use this as a tube tesla coil using a microwave oven
> transformer (2Kv)
> I also scored 2 Ducon mica capacitors .0002 at 7KV and .001 at 11KV. I
> am
> hoping these will form the basis for a decent tank circuit.
> All the above items, plus a ceramic base for the tube cost me $15
> (Australian).  The Tube was new in original carton!
> Any help on Tube Tesla coils would be most welcome.
> Regards
> Ralph Down
> Today is the tomorrow you worried about yesterday....... and everything
> is O.K.
> 
> 
Ralph,

That tube sounds like a tetrode with 1250 watts plate dissipation 
rating.  If so it will perform well in a Tesla coil provided you are 
able to deal effectively with the second grid.  I haven't really 
spent much time playing with tetrodes in a self-driven feedback 
oscillator circuit as this will be, so I can't advise you with much 
authority.  I have some 813's that I want to experiment with and I 
cannot find them since my recent move.

The obvious choices are to :

a). Tie both grids together and treat as a simple triode.

b). Tie grid 2 to the B+ supply through a suitable high wattage 
      dropping resistor.

c). Tie grid 2 to grid 1 through a dropping resistor.

d).  Tie grid 2 to the center tap of your filament transformer.

Your 0.001 mfd mica cap should be O.K. for your tank cap.  Make sure 
you provide a tuning tap on every turn of the top 1/3rd or so of your
tank
coil so you can 'dial this thing in' once the secondary is installed.

Perhaps John Freau can be of more help on this than I.

Good luck, and nice score!

rwstephens