Re: Post from newbie

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 07:50 24/02/03 -0700, you wrote:
>Original poster: "JERRY ASHLEY by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <jerryla-at-ix-dot-netcom-dot-com>
>
>Hi,
>
>I have been reading the mail for about six months but I have not seen
>much info on tetrode tube coils.

it's funny that, I suppose most folk use triodes cause they're simpler. I 
only know about the other kinds of tube because of my other hobby, building 
tube audio amplifiers.


>I have a 4-1000A tube and would like to try my hand at building a VTTC.
>I plan to use six MOTs wired in series/parallel to give twice the
>voltage and three times the current of a single transformer.  This
>should supply 4 to 5 KV at about 700 mA, close to the specs of the
>tube.  I plan to connect the raw AC directly to the plate tank of the
>tube.  I am going to use the tube in a triode configuration by
>connecting a 10K resistor between the control and screen grid and feed
>the input signal to the screen.
>
>I would appreciate any comments on this design.

You need to be careful because if you put too little current into the 
screen you won't realize the full power of this mighty tube. On the other 
hand if you use too much you'll melt the screen and turn the tube into a 
doorstop. The 10K resistor is probably too large and won't allow enough 
screen current. In any case it should go between the screen and plate. I 
would recommend you look at the 4-1000A data sheet and base your design on 
the manufacturer's conditions for a Class B Linear Amplifier. You may want 
to power the screen with AC from a separate transformer and variac to get 
the conditions right. It only takes a couple of hundred volts.

>Would I need PFC caps on the MOTs?

PFCs improve the power factor and so reduce the current draw from your wall 
outlet. Six MOTs will draw a huge current, like about 40 amps at 240V. If 
you have access to a 240 volt outlet for welder/electric cooker/AC that can 
supply this much juice then you'll have no need for PFCs. With PFCs you 
could probably get it down to 25 amps or less.

>I have some questions concerning the design of the primary and secondary
>coils.  A ballpark design in this area would help me a lot.

beats me but I'm sure there are plenty of other guys who'll chime in. A 
VTTC is very like a ham radio linear amplifier so you could always break 
out that ARRL Handbook :D

Steve C.