Re: Somewhat of a newbie..

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Ben,

My answers are interspersed below...

> 
> Original poster: "spoonMAN by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<spoonman534-at-yahoo-dot-com>
> 
> Hello all,
<SNIP>
> 
> About 6 months ago I finally built my first coil. I've
> since had ALOT of questions and I remembered that the best
> minds colaborate on this list.. Anyway, my question
> involves capicitors.. I started out using saltwater caps
> made from beer bottles.. but I realized that I had no way
> of knowing how much capacitance I had.. is there any way to
> test them or is there some general default value per
> bottle? I also ordered 4 caps vacuum sealed in a glass
> envelope rated 12pF -at- 30kV each .. they're absolutely
> beautiful.. each one is about the diameter of a soup can
> and about 8 inches long.. will these work in coiling
> applications? The glass envelope is about 1/4 of an inch
> thick and the lugs on the ends are very hefty.. they look
> like they'd survive a nuclear war...

Regular 12 oz beer bottles will be in the range of 750-900 pF/bottle. 
Vacuum caps are extremely low loss... but unfortunately they also tend to
have very low capacitance since the dielectric constant of a vacuum is
1.00000. The good news is that they are self healing if they flash over,
and some of the larger capacitance or variable capacitance types can be
used in Vacuum Tube Tesla coils, since they have NO dielectric loss. Unless
you have LOTS of them, they are not very useful in a disruptive coil.

> 
> When I was subscribed to the list way back when I happened
> on a large tube labeled "Amperex 575A".. I asked around on
> the list and I was told that it was basically a giant
> switch capable of switching extremely large currents and
> that it would be excellent for building a DC coil.. since
> then I've come across anohter and the idea of using it is
> more and more appealing.. can anyone tell me more about it?

The 575A is a high voltage mercury vapor rectifier. It could be used as a
robust rectifier in a DC coil, but it will not work well as a switch or as
a spark gap replacement. The filament takes 5 volts at 10A, and the tube is
rated for 15 kV PIV. 

The specs from the RCA Transmitting Tube Manual:

Filament voltage 5.0V
Filament Current 10.0A
Peak Tube Current Drop(Approx) 10V

Half-Wave In-Phase Operation
Maximum Ratings
Peak Inverse Anode Voltage   10000V    15000V
Anode Current
  Peak                           7A        6A
  Average                     1.75A      1.5A
  Fault (0.1 sec max)          100A      100A

Half-Wave Quadrature Operation
Maximum Ratings
Peak Inverse Anode Voltage   10000V    15000V
Anode Current
  Peak                          10A       10A
  Average                      2.5A      2.5A
  Fault (0.1 sec max)          100A      100A

A nice picture of one can be seen at:
http://www.webiosis.co.uk/valves/575a.htm

Good luck,

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

> 
> Thanks for any help!
> 
> Ben McMillen
> 
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