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Re: VTTC Resistor Values And Transformers



Original poster: FutureT-at-aol-dot-com 

In a message dated 9/8/03 8:01:54 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

>Original poster: "Adam Horden" <ath-at-blueyonder.co.uk>
>
>Hi Guys,
>
>I have found souces for the capacitors for my VTTC but finding it
>dificult to source the resistors required. As I dont know how
>componet tolerant the circuit I am building I am after some advice.
>
>The circuit I am useing is here:
>
>http://hot-streamer-dot-com/srward16/Dual833AVTTC.htm >decription and
>parts list
>
>http://hot-streamer-dot-com/srward16/images/dual%20833A_gif.jpg >circuit
>
>R1 in the picture is 30R 20W is it possible to use 33R?


Adam,

The value of those resistors is not critical.  In fact the circuit will
usually work fine without them.  It's a good idea to use them however,
because they protect the tubes in the case of an internal arc.  They
also will suppress parasitic oscillations.  47 ohms is a popular value
also.

>I can get 17W 33R from rs compoents 52 pence each. Will this be fine
>for the application even tho it is 3R out? Its ceramic body so
>winding L3 over it could be a difficult task.


If it's ceramic with a perpendicular tab at each end, it's possible to
wind the wire over the resistor.  I like to leave a space between the
wire and the resistor.  To do this, I space-wind the wire around a larger
diameter dowel or something, and then "screw" the wire onto the resistor,
so it screws over the perpendicular tabs.  It's a little tricky but comes
out great.


>R2 I have been told 5K work work here. I can get 1K 100W and put 5 in
>sersies. I can also get 4.7k 72W would this work?


Generally not super-critical.  4.7k should be fine.  An adjustable
resistor is nice if you can find one.  Tube coils tend to require a lot
of adjusting and tweaking for best results, of course if you copy an
existing design, it makes it a lot easier.  The trick is to get long
sparks, without the tubes getting too red.


>Does any one know where I can get 10V 10A transformers? I require
>two or one 10V 20A unit for the filimant supply.


Some folks just wind about 10 turns (or whatever is needed)
of 10awg wire in place of the
original filament winding on an MOT.  This will easily give you the
20 amps.  Be sure to adjust the voltage to the tubes by measuring
the voltage at the tube pins with the tubes lit.  Bring the voltage up
with a variac slowly so you don't over-volt the filaments.  Run the filaments
at 10.2 to 10.5 volts.  Somewhere in that range should be good.

Regards,
John


>Thanks
>
>Adam
>