Re: More tube coil stuff (Carl Willis)...

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 9/2/00 6:45:15 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

> What is needed is an SCR that can handle about
>  20 - 40 amps and 600 volts...that kind of fat.  (I don't understand why 
they
>  don't need to stand up to the full plate potential, since it seems to me 
> that
>  the floating cathode would lose electrons to the plate until it was at the 
> same
>  voltage.  Can someone explain?) 

Carl,

I guess when the SCR is off, it doesn't let any tube plate current
flow, so the plate voltage is not seen by the SCR.  The tube is
basically like an open circuit... like the tube was physically
removed from the circuit.  Of course when the SCR is conducting
then the cathode voltage is very low, so that's a safe mode too.
On and off switching/enabling occurs during the negative ac half 
cycle when there's no current flow.  

(Carl,  I saw your other posting about getting longer sparks in 
steady operation (non-sputter/non-blocking), thanks for the update.)

John Freau
----

> This kind of part is usually a stud-mount
>  thing.  I tried to order one a while back from a surplus joint, but first 
> they
>  wanted $17 for it and secondly they didn't have it in stock.  They're not 
> hard
>  to come by, I just don't feel right spending more for the SCR than I did 
for 
> my
>  tube (ten bucks).  
>  
>  >>>(One of these days I will get around to putting together a true staccato
>  >>>driver and I'll put a big fat SCR in the cathode lead for it.)
>  
>  
>  >I've got a big fat SCR....ideas?
>  
>  Make a tube coil and use it for staccato.  Or, give it to me!!
>  
>  Christopher A. Boden Geek#1