# [TCML] Tiny VTTC

tesla popp teslas_lab at yahoo.com
Mon Jan 25 20:32:58 MST 2010

```SO AWESOME! Thank you. So ive got a tube coil now! so far it's droping 1.5 inch sparks and there HOT.  Thanks for the schematic too, I have made some adjustments to the schematic to force it to work (by over driving the grid and jump starting the thing), but i am not sure how to figure out the proper value for the biasing resistors.  The tube is obviously getting very hot, very quickly. I DO have all the necessary equipment to take any measurement you require to answer these questions.

Once I get everything biased correctly I will use an oscilloscope to perfectly match the frequency of the tank circuit with the secondary (via adjusting capacitors and secondary top-load.

now my questions are: How do i calculate which grid needs which resistor?  i dont fully understand my tube's datasheet,  I dont see any referance to proper grid current, just to grid voltage.

And; other than the tank capacitor, what is the purpose of the other capacitors?  Do they have anything to do with tuning? Or are they just to stabilize voltage between cycles (high frequency cycles)

Thanks again for the top notch tips.

,Jeremiah Popp

> Subject: R: [TCML] Tiny VTTC
> To: "'Tesla Coil Mailing List'" <tesla at pupman.com>
> Date: Monday, January 25, 2010, 1:52 AM
> Hi Jeremiah, You can try to wind the
> same number of turns for the
> feedback coil, spaced from the tank coil by 1/2 inch. Bias
> resistor for
> screen grid can be 10K 10W, then you can choose a grid leak
> resistor in
> order to have a plate current which meet the datasheet of
> the tube.
> The grid leak capacitor can be 1nF, then you can adjust the
> tank
> capacitor for max out voltage. If you have no oscillations,
> you must
> reverse the connection of grid or tank coil.
>
> An example of this coil is here
>
>
>
> And some ohotos here
>
>
>
>
> -----Messaggio originale-----
> Da: tesla-bounces at pupman.com
> [mailto:tesla-bounces at pupman.com]
> Per conto
> di tesla popp
> Inviato: lunedì 25 gennaio 2010 3.33
> A: Tesla Coil Mailing List
> Oggetto: [TCML] Tiny VTTC
>
>
> I would very much like to construct a Tesla coil with a
> have.  The tube is a 6DQ6-B.  It is a 770 volt,
> 18 watt beam pentode
> tube.
>
> The datasheet is here:
> http://pdf1.alldatasheet.com/datasheet-pdf/view/117732/GEC/6DQ6B.html
>
>
> I looked for about an hour online trying to find a coil
> with simple
> schematics for a tube like this, but to no avail.
>
> Using the "WinTesla" program, I designed a coil which I
> could feasibly
> make based on the materials i have on hand
>
> Secondary 1" wide x 4.5" tall.  36 AWG wire.
> 1/4 wave Frequency: 1.45MHz
> Toroid will be a 1/4" x 1.5" steel washer.
>
> Primary coil 1.7" wide, helically would coil.
> 15 turns of 20 AWG wire.
>
> Capacitor .0120 uf
>
>
> Things i am not experienced enough to figure out alone are
> as follows:
> What sort of biasing resistors should i use.  Is there
> a similar
> schematic of a coil using a tube this small?  how many
> feedback windings
> do i need?  What distance from the primary coil i
> should begin winding
> the feedback coil?  what other questions should i
>
> I have NEVER used a tube before with success.  Any
> help would be greatly
> appreciated.
>
> thanks for your input.  I'll post lots of pics in
> if i get it working.
>
>
> ,Jeremiah Popp
>
>
>
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