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 Post subject: Colpitts Oscillator Tesla Coil
PostPosted: Jul Sun 14, 2019 5:58 am 
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Joined: Oct Wed 04, 2017 12:27 am
Posts: 144
I was wondering if anyone has ever tried using a Colpitts Oscillator to drive a vacuum tube tesla coil? I built a Hartley Oscillator type coil a few years ago and it is really trouble free and seemed to yield better output than Armstrong setups. So naturally I've been pondering designing a Colpitts coil using a series capacitor voltage divider for grid drive. Does anyone have any experience to share?


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 Post subject: Re: Colpitts Oscillator Tesla Coil
PostPosted: Jul Mon 15, 2019 12:14 am 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9832
Location: Santa Rosa, CA
I've never built a VTTC (vacuum tube Tesla coil). Have built some neon sign spark gap TCs.

Do you really need to drive a TC with a separate oscillator? Old time TCs and induction heaters used one power tube as an oscillator and some didn't even use DC power. The coil operated at 50% duty.

Image

Rich


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 Post subject: Re: Colpitts Oscillator Tesla Coil
PostPosted: Jul Mon 15, 2019 6:57 pm 
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Joined: Oct Wed 04, 2017 12:27 am
Posts: 144
I really was referring to how the primary/ tank circuit is connected. Not a separate oscillator. Rich, I was curious where you found that schematic? I've never run across it. It appears to be a Hartley type, like mine, with the tapped inductor primary. The Colpitts version I've been pondering is a lot like it but the entire primary is tapped and instead of one tank capacitor (C1), there would be two. Between them is tapped to drive the tube grid. I thought this design might make a neat vacuum tube bipolar coil since the primary wouldn't have unused windings for tickler coils and such. One thing that occurred to me today sketching schematics was that the series capacitors wouldn't have any discharge path when the coil was turned off. Of course I always use bleeder resistors but prefer that they only be redundant.


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 Post subject: Re: Colpitts Oscillator Tesla Coil
PostPosted: Jul Mon 15, 2019 10:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3871
What's going on with T2 @ 1500 V connected with the heater and 6.3V winding of T1?


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 Post subject: Re: Colpitts Oscillator Tesla Coil
PostPosted: Jul Mon 15, 2019 10:54 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9832
Location: Santa Rosa, CA
There is no rectification. One side of T2 goes to the heater, essentially B-. The other end of T2 goes to the primary of L1.

https://www.montagar.com/~patj/tes3.htm

Rich


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