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My First Mini 811a Tesla Coil

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TwirlyWhirly555

Thu Mar 01 2012, 02:21PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

Hi ,

I finnaly got round to making a mini 811a tesa coil , specs are

Tube : 811a
Supply : Half wave 2kv from MOT

Primary - 18 Turns 0.5mm Wire ( to thin it gets stupidy Hot )
FeedBack - 16 Turns of HookUp Wire

Grid Resistor 5K Ohm , ( need larger W Rated resistors though )
Grid Capacitor 780pF 30Kv

Tank Capacitor 780pF 30kv ( Thanks gren :) )

Seondary - 1" x 6" 5.5" worth of windings 28 AWG wire .

It runs ok , with no top load i get not bad arcs , Anode will become a faint red after a min or so , But primary is smoking .

With a 1 3/4 " topload i get nice arcs , anode will redden quicker .

With 3" topload i get long arcs but anode is red pritty quick ( 2 - 3 seconds )

So my main thing id like to ask is , does the primary and feedback turns sound ok , i know adding a larger topload will bring fres down , but if i add anothere cap i still get reddening . probably pushing to puch power through this all . Im still leraning :)

This is a video with 3" topload .

All the best
Twirlywhirly555

Patric

Thu Mar 01 2012, 08:23PM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Fantastic result! I attached the schematic of my coil, I had to regulate the power, because I would the coil be working for longer time without the 811a becoming red. With min power the coil works for hours and a spark of +/- 1 inch, at full power the 811a becomes slowly red, but the spark is about 4 inch.

TwirlyWhirly555

Thu Mar 01 2012, 09:00PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

Patric wrote ...

Fantastic result! I attached the schematic of my coil, I had to regulate the power, because I would the coil be working for longer time without the 811a becoming red. With min power the coil works for hours and a spark of +/- 1 inch, at full power the 811a becomes slowly red, but the spark is about 4 inch.

Thanks :) , Hmm yeah i have it now i get about 4-5" arcs but tube will redden within 10 seocnds or so , Ill build that power control you used in that circuit :D , i have no real way to tune better than what i have managed to get , i used a calulator online and got a frez of 800 Khz , cap tank needed was 780pF , so im close but im pushing over 300W into the coil , so tube pays for it .

here are pics of the finished coil , 15 primary turns . and HDD platter as topload .

Patric

Fri Mar 02 2012, 11:00AM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Looks good, nice sparks!

Here is a little presentation of my Tesla coil, "The making of..."

http://www.youtube.com/watch?v=H7nivw7zxNM&list=UUJzdWsFdhAj-X1uA8fXoGeQ&index=7&feature=plcp]

TwirlyWhirly555

Fri Mar 02 2012, 03:26PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

Patric wrote ...

Looks good, nice sparks!

Here is a little presentation of my Tesla coil, "The making of..."

http://www.youtube.com/watch?v=H7nivw7zxNM&list=UUJzdWsFdhAj-X1uA8fXoGeQ&index=7&feature=plcp]

Thanks :D , Nice video and coil :) , I finnaly have mine making 3" arcs and no reddening :D .

Patric

Fri Mar 02 2012, 04:29PM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Thanks :D , Nice video and coil :) , I finnaly have mine making 3" arcs and no reddening :D .

Congratulations! How you did it?

TwirlyWhirly555

Fri Mar 02 2012, 07:11PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

Patric wrote ...

Thanks :D , Nice video and coil :) , I finnaly have mine making 3" arcs and no reddening :D .

Congratulations! How you did it?

Hi , Thanks :) , Well i have 4 capacitors in the tank , 2S2P to give around 700 something pF , there is a fan on the primary and the tube stays normal colour , but if i arc to a object the tube will turn a faint red . The capacitors run warm , not sure if thats normal ?

Heres a video of the coil acs now , can run for ages :D

Patric

Fri Mar 02 2012, 08:16PM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Looks really good! It is normal that the capacitors are warming up, must be they are not the perfect kind. Mine get slightly warm too. Some real specialists here can tell which capacitors to use. I should not be worried.
Many greetings!

PhilGood

Sun Mar 04 2012, 09:41PM

Registered Member #3806 Joined: Sat Apr 02 2011, 09:20PM
Location: France
Posts: 259

Patric wrote ...
...
Here is a little presentation of my Tesla coil, "The making of..."

http://www.youtube.com/watch?v=H7nivw7zxNM&list=UUJzdWsFdhAj-X1uA8fXoGeQ&index=7&feature=plcp]

Good job TwirlyWhirly555 !

And nice work, great and very interesting video, Patric. It gives good ideas for components mounting.

(I plan to build a 811A mini VTTC as 2nd coil after I'm done with EVR microBrute DRSSTC)

Thanks both for sharing :)

LuceÅ¡

Mon Mar 05 2012, 04:17AM

Registered Member #4108 Joined: Sun Sept 25 2011, 11:43PM
Location:
Posts: 149

Hi that is amazing for a single 811a! I found out the hard way that you must use good capacitors

anyways get some big capacitors rated in Kvar and if you crank the Q the capacitor will take more of the heat than the tube.

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