[Noisebridge-discuss] High-Voltage

jim jim at well.com
Mon Mar 11 22:03:11 UTC 2013

    Great rant on science (at bottom)! 

    My vacuum tube experience is with audio stuff; 
the tubes used for radio frequency broadcasting, I 
believe, are pretty different. 
    Vacuum tubes voltage requirements are generally 
wide. The specs typically reference a close-to-max 
rating. A tube that can handle 500VDC likely can 
work with as little as 100VDC, although its affect 
to signal will be different depending on voltage 
level: audio signals will be cleaner with high 
voltages and "browner" (the classic compressed 
peaks) with lower voltages. 

    What project ideas do you have in mind? 

On Mon, 2013-03-11 at 14:08 -0700, John Butterfield wrote:
> Honestly I haven't done much with vacuum tubes yet, so I'm not that
> familiar with their operating voltages.  I guess if you make your own
> you can tune them for whatever voltages you want.
> I've built a couple of my own hv power supplies.
> Since LCDs have completely displaced the use of CRTs, people are
> always junking their old CRT TVs and Monitors.
> I had an endless supply of these, and I figured I'd learn how to build
> a high voltage power supply from one.
> I didn't have much experience going into it, but I succeeded on my
> first one and it still works >< So now I just have an excess of crt
> monitor flyback transformers and mainboards waiting to be gutted for
> their 2kv capacitors and power mosfets.
> The only though I purchased was a few 555 timers.  Which I did need a
> few of because it took me a while to learn how NOT to fry them with
> kickback voltage from the transformers.
> Anyway, as for how high, I guess it depends on the application.
> With a flyback transformer you can go from around 20-60kv depending on
> the flyback and the age of the crt it came from.
> These power supplies are quite low current.
> I also built a power supply using 2 MOTS (microwave oven
> transformers), which spits out around 4kv at at a very high current.
> They behave quite differently, and it's interesting to work with both.
> One of my favorite papers from Tesla is his article On Light and Other
> High Frequency Phenomena. In it he talks quite a lot about the
> characteristics of the high voltage power supply he used as the source
> for many of his experiments. One of the characteristics, he described
> was that often it was hard to draw an arc, and so his spark gap had a
> handle with a spring that he could use to temporarily reduce the spark
> gap distance to get things started, and then he finds that once the
> arc is formed it wants to stay formed which is why he started creating
> all kinds of new ways to blow the arc out once it formed.  One of
> which being just using a magnetic field.
> This puzzled me at first as I was using my flyback transformer and
> there characteristics were very sharp sudden discharges and they had
> no problem forming at all. It wasn't until trying the MOTs that I saw
> a different side of the story. Using the MOTs, the voltage was much
> lower like around 2kv when I started, and I too found that it was
> difficult to form the arc, it required a very small spark gap
> distance. And also, once formed due to there being much more current,
> the arc stayed formed and grew like a flame even as I widened the gap.
> Here's one of my first tests with the flyback transformer:
> https://www.youtube.com/watch?v=tWsPwynGP_c
> Here's the same thing but now with a capacitor (With more current per
> discharge, the magnet is more effective at disrupting each burst from
> the cap)
> https://www.youtube.com/watch?v=p9llYS_3s5Y
> Here's some videos using the MOTs
> https://www.youtube.com/watch?v=EtLlAljKQ4g
> There are free energy advocates who have made claims about phenomena
> associated with certain types of HV discharges.  My personal stance on
> the subject is, I think people who advocate ideas without any kind of
> evidence or scientific approach are a burden to the scientific
> community. However, I'm also disappointed in a large part of the
> scientific community who outcast any and all work related to the
> claims of such extremists. Both viewpoints are equally dogmatic and
> have no place in science.  That said, the side of having a large body
> of evidence suggesting something works a certain way, and then hearing
> claims made that it may behave differently is understandably
> dismissible as IMPROBABLE, but I would not go as far as to condone the
> claim as false right out. I think it's important for people to revisit
> largely accepted ideas and attempt to poke holes. I wouldn't spend MY
> time trying to make a mechanical perpetual motion device, and I'd
> probably think it fruitless for whoever tries, but if someone is
> adamant about doing it, I wouldn't try to convince them otherwise. So,
> all that to say, I'm not opposed to exploring some claims even if they
> come from not so reputable sources.
> `John
> On Sun, Mar 10, 2013 at 11:02 PM, John Ellis <neurofog at gmail.com>
> wrote:
>         CRTs go up to around ~24KV at the Extra High Tension supply.
>         Transformers, more specifically, the Line-Output Transformer
>         can be good for high voltage experiments.
>         -John
>         On Sun, Mar 10, 2013 at 11:37 AM, jim <jim at well.com> wrote:
>                     I'm interested and willing to help.
>                     What do you mean by "High voltage"? I'm thinking
>                 anything over 240 VAC (about 360V peak to peak).
>                     Vacuum tubes work with anything from about 60VDC
>                 to
>                 500VDC (or so).
>                     440VAC circuits have of close to 700V. Mircrowave
>                 ovens I've seen have transformers that present
>                 internal
>                 voltages to something like 800V. Cathode ray tubes use
>                 from 1500VDC to 5000VDC.
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