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 Post subject: Simple Tesla coil
PostPosted: Nov Sat 25, 2017 7:28 am 
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Years ago I found a schematic for a fairly simple VTTC that doesn't require winding 100s of turns of fine wire. I even gathered some of the parts for it. Recently I found the circuit on the Americanradiohistory site. It can be built without the capacitance circuit. It only needs 7 parts. I am sure that it puts out a lot of RFI as well. It could also use a fuse on the primary of the transformer as well. At some point I would like to build it.


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 Post subject: Re: Simple Tesla coil
PostPosted: Nov Sun 26, 2017 8:06 am 
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That oscillator (the lower one on the schematic diagram cited) might not be strictly considered a Tesla coil, for it lacks a self-resonant winding with an output terminal at high R.F. potential. Such a winding could be added, but then it would be desirable to add a provision for tuning the primary circuit to the Tesla coil.

The frequency in this case appears well into the shortwave range, so a self-resonant coil would not have a great many turns. It will work, and produce a corona discharge, but in general, performance may be disappointing.

This circuit is probably similar to that of the Sun Kraft ultraviolet lamps that used an electrode-less quartz tube, excited by a shortwave power oscillator.

A good, small vacuum tube Tesla coil project, that does not require winding a coil, would be “Li’l TC” from the July 1964 issue of Popular Electronics:

https://teslauniverse.com/resources/bui ... ans/lil-tc

The data sheet for the Miller #4526 high voltage coil can be seen here:

http://antiqueradios.com/forums//viewto ... 9&t=239814


Last edited by Philip Colston on Dec Wed 06, 2017 10:46 am, edited 1 time in total.

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 Post subject: Re: Simple Tesla coil
PostPosted: Nov Sun 26, 2017 7:14 pm 
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Philip Colston wrote:
That oscillator (the lower one on the schematic diagram cited) might not be strictly considered a Tesla coil, for it lacks a self-resonant winding with an output terminal at high R.F. potential. Such a winding could be added, but then it would be desirable to add a provision for tuning the primary circuit to the Tesla coil.

The frequency in this case appears well into the shortwave range, so a self-resonant coil would not have a great many turns. It will work, and produce a corona discharge, but in general, performance may be disappointing.

This circuit is probably similar to that of the Sun Kraft ultraviolet lamps that used an electrode-less quartz tube, excited by a shortwave power oscillator.

A good, small vacuum tube Tesla coil project, that does not require winding a coil, would be “Li’l TC” from the December 1964 issue of Popular Electronics:




















































https://teslauniverse.com/resources/bui ... ans/lil-tc

The data sheet for the Miller #4526 high voltage coil can be seen here:

/viewtopic.php?f=19&t=239814


I know about that circuit, but the coil is unobtainium. :( I do have the 4525 coil, but that puts out a much lower voltage. I remember several decades ago, I worked at a company that had an old adjustable 16 kv power supply. It had a 5U4, 6L6 and a 1B3 tube on the output. It had a coil kind of like that one. It had a meter on the front and a big fat output cable coming out of it. If I had known about that coil, I would have kept the power supply. It probably got scrapped long ago. I do have some small Tesla coils that I got off of ebay. They aren't that powerful but they are fun to play with.

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 Post subject: Re: Simple Tesla coil
PostPosted: Nov Mon 27, 2017 9:46 am 
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Actually, examples of the Miller #4526 high voltage oscillator coil show up for sale every so often, usually new in the box. I had an advertisement on the ARF Classified section several years ago, which turned up a Merit-branded version of the coil. I then found two Miller-branded versions on eBay, one of them with green coloured wire, and have seen others sell on eBay. With patience, you will undoubtedly find a Miller #4526.

Note that an oscillator built with the Miller #4525 can be just as powerful in terms of R.F. output, though the high potential will be lower.

It was once common for high voltage power supplies to be based upon vacuum tube Tesla coils of this kind. Some used the Miller #4526 or #4525, but others used custom coils of similar construction. I have such power supplies of 60, 30, 20, and 10 kilovolt output.

The concept is still employed in high voltage power supplies, but the driver circuitry is now solid-state.

The first vacuum tube Tesla coil was constructed by the famous pioneer radio amateur John Reinartz in 1923. The late, and greatly missed, ARF member Alan Douglas created a beautiful, faithful replica in 1977, with period components.

https://www.radiomuseum.org/r/reinartz_ ... ebrew.html


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 Post subject: Re: Simple Tesla coil
PostPosted: Dec Sun 03, 2017 2:11 am 
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This thread inspired me to upload this video demonstration of my Li'l TC that I built for my 7th grade science fair project in 1966. I reconstituted the circuit using my Miller 4526. I had to repair the HV secondary for this effort, because it was damaged at the science fair by a couple of doofus kids fooling around with the arc. I performed this effort and the filming in summer of 2015.

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 Post subject: Re: Simple Tesla coil
PostPosted: Dec Wed 06, 2017 7:02 am 
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random73 wrote:
This thread inspired me to upload this video demonstration of my Li'l TC that I built for my 7th grade science fair project in 1966. I reconstituted the circuit using my Miller 4526. I had to repair the HV secondary for this effort, because it was damaged at the science fair by a couple of doofus kids fooling around with the arc. I performed this effort and the filming in summer of 2015.

-73


Thanks for posting that! The circuit changes are good to keep in mind if I ever get to build it.

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 Post subject: Re: Simple Tesla coil
PostPosted: Dec Wed 06, 2017 10:44 am 
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Note that connecting anything to the output terminal of the secondary winding of the Miller #4526 coil, such as the anode of a rectifier tube, or a long lead, will lower its resonant frequency, necessitating more capacitance in the primary circuit. In Li’l TC, the only secondary load was supposed to be a sewing needle attached adjacent to the coil body.


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 Post subject: Re: Simple Tesla coil
PostPosted: Dec Thu 07, 2017 7:16 am 
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Okay, I'm glad that we got that cleared up. I was wondering why the article was so far off compared to the actual circuit.

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