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Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
I am relatively new to the hobby, and insofar have only built two coils. The first one was made of whatever I could find around the house, 150 feet of 26 gauge rubber insulated wire for a secondary, and 2.5 turns of 18 gauge for the primary. It gave reasonable performance with .75-1.25 inch streamers and a 3 inch very faint corona. It also used a camera flash circuit and 18 stage CW multiplier along with a 1nF plate glass cap. Reasonable performance for something that didn't take any money to build.
The next one is the one I am having trouble with. It has 440 turns of 30 gauge magnet wire on a 1.71"x5.25" secondary with a 2.5" spherical topload and a max of a 3 turn primary, and it is tuned best at about 2.25 turns. Tank cap is two 20nf rolled overhead slide caps in series. I am driving it with a single transistor flyback, at a guestimate 5kv. I was hoping to get performance of at least two inch streamers similar to this one, but I am getting absolutely no corona and .5 inch streamers to a ground. Any thoughts as to how to improve performance? I would post pictures, however both of my cameras are out of commission for the moment.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
...and the flyback output is rectified, right? It would have to be. Otherwise you'd be trying to charge your 20nF cap some number of thousands of times per second, which obviously won't work. And if it did, then you'd be trying to push thousands of breaks/sec on a spark gap, which isn't going work too well either.
But if that isn't it, it couldn't be a zillion other things I don't suppose I have to tell you that you're definitely doing things the hard way. Rolled caps are much harder to get right than "beer bottle" types, for example, and flybacks and their drivers obviously represent a boatload of new opportunities for failure next to a NST or some such.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
Thanks for the luck Aaron, I guess I'll need it.
And yes, the flyback one of the newer, internally rectified ones. The driver has been holding up admirably to the abuse I've been putting it through, like testing the rolled caps for instance.
I would love to get a 4-8kV NST, however I don't have the money for an Ebay model, so I am relegated to searching around here, hoping someone burnt out their neon tubes, and thinks the whole thing is bad.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
First of all the tesla coils that use flybacks use a powerful driver that can go up to a few 100's of watts. Second of all the use i think it is around 3nf capacitors.
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SGTC Newbie Questions
I don't suppose I have to tell you that you're definitely doing things the hard way. Rolled caps are much harder to get right than "beer bottle" types, for example, and flybacks and their drivers obviously represent a boatload of new opportunities for failure next to a NST or some such.