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4hv.org :: Forums :: Tesla Coils
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Beginner tesla coil, doen't work

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Dash_Riprock
Mon Apr 07 2008, 02:47AM
Dash_Riprock Registered Member #1431 Joined: Sun Apr 06 2008, 04:59PM
Location:
Posts: 6
I was afraid of that... of course, the problem is the most expensive part.

So is it a bad idea to get a used NST? Do these things have a very long lifespan if used on an actual neon sign, or is it likely to burn out on me? I dont really have the cash to buy another new one.
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MOT_man
Mon Apr 07 2008, 02:54AM
MOT_man Registered Member #1127 Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
nope... ask around. I got my 12 kV 60mA NPF franceformer NST from a local sign dealer... used. Works fine :) I bought the guy some beer - he was happy :) NSTs need line filtering to get the RF from destroying these tightly wound coils. I use a Terry filter - look up this term on Link2 I currently use 3 - 12kV 60mA transformers in parallel. One is PFC corrected transformer - total power output 1700 -1800 watts @ 12kV. Streamer length - constant strikes at 66" - sometimes an odd 70" streamer - guessing this is a fluke.
I've used this power supply for 2 years on and off for demos - not one failure.
Microwave ovens are plentiful too. The transformers are vastly more powerful - and deadly but lower voltage... they can be had for cheap too. Repair shops are throwing out older models because transformers are recycled. Don't go to the PT / PMDTs yet --- VERY DANGEROUS!
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vasil
Mon Apr 07 2008, 10:38AM
vasil Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506
A "heavy" NST is a good choice. Though if you have the time to spend, and two flybacks (one AC and the other DC), you can try to get a reliable DC output, through a transformer chain (of course you will loose some power in the process). The approximative schema would be somthing like THIS
Use the AC flyback in reverse (the output of the solid NST in the secondary of the AC flyback) and wind your own primary, 6-10 turns with solid heavy wire. Use the same number of turns for the DC flyback primary. With a bit of luck you would get a DC output from the second flyback. Have to tincker a bit with the seried capacitor to get the best output.

The schema is just a sugestion, I didnt make it.
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quicksilver
Mon Apr 07 2008, 02:52PM
quicksilver Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Dash, I'm new to all of this as well but I think there are two gold stars here....First the coil is perhaps, very much out of tune but that could be dealt with. The most significant is the transformer. I obtained a NST and never looked back. BUT I think the idea of using your present transformer with a flyback setup is a damn good one.

I was looking at Vasil's idea and it's a really one of the better ones for not dealing with a lot of hassle (given that you could get the flybacks for free, etc).

As soon as I saw the three colours of wire I knew where you got your 2nd coil wire from.....That alone could spell a lot of trouble. but it's not a total loss. Most everyone learns doing just what you are doing! What I do now is when I get into a place of non-functionality with a project, I start making lists of what I need to do to eliminate the variables and problems. I really see only two. The coil and the transformer. The flybacks should deal with that neatly and the coil will at least allow SOME functionality to prove it one way or another.
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Ultra7
Mon Apr 07 2008, 03:09PM
Ultra7 Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307
MOT_man wrote ...

NSTs need line filtering to get the RF from destroying these tightly wound coils. I use a Terry filter - look up this term on Link2

Or just go here.
Link2
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Dash_Riprock
Mon Apr 07 2008, 08:16PM
Dash_Riprock Registered Member #1431 Joined: Sun Apr 06 2008, 04:59PM
Location:
Posts: 6
Ok, thanks a ton from everyone for all the help. I'm just going to try to find a used legit NST and go from there. Im not going to go through all the trouble of making a new secondary unless I find out for sure that my current one is a problem, since I have to reason to believe that it is other than slightly higher resistance than there should be.

One more question though: My current capacitor setup reads 3nF on my multimeter. I read online that the capacitor should be sized such that it fills up once each half cycle of the power supply. This means that

3E-9F * 10E3V = 30E-6 coulombs
30E-6C / 30E-3A = 1 millisecond
((1/60)s/2) / 1E-3s = 8.4

which means that my capacitor is 8 times too small!! Can a coil run well despite this, am I not calculating this right, or is this a major problem?
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Ultra7
Mon Apr 07 2008, 08:23PM
Ultra7 Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307
I have 7 legit NST's, if you just happen to live in Houston.
If not, good hunting.

Do you have Teslamap yet?
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Andyman
Mon Apr 07 2008, 08:44PM
Andyman Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256
Size of capacitor won't cause the coil to fail. Just as long and the primary and secondary circuits are properly tuned. I run my mini magnifier coil with a 1nf capacitor (even smaller than yours) on a 12kv 30ma nst and I get 3-5 inch arcs from it. Also, it's best to use a capacitor 1.3 to 1.5 times greater than that resonant value. If you run at exactly resonant, the NST will experience huge resonant rise and die.
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Andyman
Mon Apr 07 2008, 08:44PM
Andyman Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256
EDIT: Oops, what on earth? My post appeared twice! confused
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