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Why am I getting no streamers?

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Sulaiman

Wed Oct 24 2007, 08:59PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Those are 0.15 uF capacitors, 15 in series gives 10 nF which is correct for a 10.5/30 NST.

Is your TC wired correctly like the first diagram here ?

Tenicus

Wed Oct 24 2007, 11:23PM

Registered Member #864 Joined: Tue Jun 26 2007, 07:26PM
Location:
Posts: 22

Yes.
Is it possible that I blew a cap?

ShawnLG

Thu Oct 25 2007, 01:57AM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

Is your NST modern solid state or is it the old ones that are heavy?

Tenicus

Thu Oct 25 2007, 02:15AM

Registered Member #864 Joined: Tue Jun 26 2007, 07:26PM
Location:
Posts: 22

Its an old allanson. Good for tesla coils
Its not a new small black box

I was looking at MMC today and I didnt do a great job soldering-- there is some overlap..... could that be the problem?
Im just throwing things out here

ArcLight

Thu Oct 25 2007, 08:42AM

Registered Member #341 Joined: Thu Mar 23 2006, 07:41PM
Location: Northern Illinois, USA
Posts: 69

I'm not going to mislead you, for whatever reason I have a difficulty conceptualizing the interaction between electronic devices. Because of said difficulties, I have probably made more stupid errors (and consequently more fires) than anybody else here. However, because of the simple explanations on this site (and slowly learning from the above mentioned fires) I have several fine working coils even if I don't fully understand them.

Assuming that you have wired everything correctly (the sparkgap in parallel with the power transformer and the cap bank and primary in series with the gap) tell us about your gap. Do you have forced air through the gap? If you don't have any forced air through the gap, it may be just be power arcing. If that's the case you will get very little or no secondary output. If you do have forced air (and if you don't now, you will in the future,) what does the gap sound like? If you're even close to being in tune, it should look and sound like an arc welder. If instead it's a loud raspy sound then you're way out of tune.

I once had a fine working coil, and decided to add 50% more transformer and consequently 50% more capacitance. Because of screwed up thinking, I also added 50% more inductance. There was no output from the secondary and the sound from the gap was truly frightening. Once it dawned on me what a weenie I was and moved the primary tap the other direction, the gap quieted down and the coil went to running wonderfully.

If you suspect that one of your caps has failed, just turn the lights off and power up the coil. If one of the caps has failed, it will be obvious immediately because of the fire inside the cap. Said fire will burn through the side of the cap after a few seconds. Trust me, I have killed several of the 942's when using one string of 10 for a 15Kv 60Ma transformer. It was immediately obvious which cap had failed. I now use two strings of twenty and have had no failures of any kind after several hours of run time. So one string of fifteen should serve you quite faithfully.

Keep working at it. The resulting roar of your own coil is quite rewarding and well worth the effort.

Regards, ArcLight

Tetrafluoroethane

Thu Oct 25 2007, 01:15PM

Registered Member #127 Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44

It is possible you blew a cap, but unlikely. Those caps can take a ton of abuse and you are not pumping all that much power into the system. And, like ArcLight said, when they fail, they tend to fail in flames.

I would break the testing down into stages and try to elminate one component of the system at a time. Try this:

1) Use a DMM to test the resistance of all the primary connections (spark gap to primary coil, primary coil to cap bank, and cap bank to spark gap). If any of those connections shows more than a couple ohms, find out why and fix it. I don't suspect this is the problem since if you had a high resistance connection here the gap should be just as likely to fire in the tank as it is with the NST alone since the charging of the cap wouldn't be pulling the voltage down.

2) Use a DMM to test the resistance of the feed lines from the NST terminals to the spark gap. A high resistance connection here *would* make the gap less likely to fire since the current coming from the NST is going to be limited by the connection.

3) If your DMM measures capacitance, measure your cap bank. Is the expected value close to the measured value? If not, check each cap individually and see if one is way out of spec. They will all vary slightly, but after you measure a couple you should get a feel for what is normal.

4) Set your spark gap to just under where it fires with the NST alone. Leave the cap bank and primary coil disconnected from the gap and turn on the NST. Basically run the gap in place, just with the tank disconnected. If it doesn't fire, the problem is with your feed lines. Make sure they aren't sitting on the ground or too close together. I used wire rated for 15KV and I still get energy loss on the lines from the NST. I try to keep them as far away from each other as I can and off the ground.

5) Hook the cap bank in parallel with the spark gap (bypass the primary coil) and turn the system on (just for a sec as this can be really hard on the NST). If the gap stopped working the problem is either with the cap or the wires feeding it. Maybe you have a short somewhere? If the soft buzzing of the spark gap turned into a roar, you are good.

6) Put the primary coil back in the circuit and tap it at the first or 2nd turn. Take the secondary out of the circuit. Fire it up and see if the gap is still really loud (just like #5). Keep repeating this and tapping the primary further out each time. NOTE: move the secondary several feet away as it can still generate high voltage from the primary's magnetic field just by being in proximity!

7) Make sure the tap on the primary coil is tight and that it does not bridge to another turn. Mine was crappy and I didn't notice it bridging to another turn for a while. When I eliminated that short the coil took off. The bridge to another turn was acting like a single loop (like a closed strike rail) and sucking energy out of the system).

If you get this far and the gap is roaring at a distance of around 5mm, your primary circuit is good to go. Add the secondary and everything should light up (after some tuning of course).

If you have pictures of your setup that might help.

Good luck.

Tenicus

Thu Oct 25 2007, 08:46PM

Registered Member #864 Joined: Tue Jun 26 2007, 07:26PM
Location:
Posts: 22

Thank you for the informative posts.
I will try that as soon as I can.

Tenicus

Sat Oct 27 2007, 03:16AM

Registered Member #864 Joined: Tue Jun 26 2007, 07:26PM
Location:
Posts: 22

I couldnt find my multimeter so I started at 4
With only the mmc in parallel, nothing happened
fired once then stopped

For wires I just used the wires from an extension cord
I cut away the insulation at the end and wrapped it around whatever its being attached to
Is this a problem?

I also got a bad ass shock from the sparkgap
arm flew back and punished the bowflex

Myke

Sat Oct 27 2007, 05:57AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

ALWAYS discharge caps before working on them. You should make the connections better than just wrapping the wires around the leads because if one comes loose it might be a problem.

Tetrafluoroethane

Sat Oct 27 2007, 03:02PM

Registered Member #127 Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44

Sorry to hear about your shock. I hope you are okay. Was the power applied when you got the jolt? Or was it residual charge in the cap bank? If it was residual, put on some bleeder resistors. They really do help make cap banks safer. I never had any residual charge in my cap bank (and I know this because I always shorted the thing with a screwdriver before I touched anything). Maintain absolute focus at all times and always be thinking of what the dangers could be. Be paranoid and you will live to arc another day.

Did you use extension cord wiring for everything? NST -> Gap -> Cap & Primary? If so, are you keeping all the wires seperated well? The insulation on those wires is not meant to stand up to 10kV (it is usually rated to around 600V) so you can't have them too close to anything at a different voltage potential. Even laying on the ground might cause them to arc.

My feed lines buzz when laying across concrete and they *are* rated for 15kV. And using smaller gauge wire (14ga or 12ga) might be a little small for the wiring in the primary circuit. It still should work moderately well, but your I^2R losses are going to be higher than the would be if you went with a 6 or 4 gauge.

Myke is right. You need nice firm connections between everything. I find threaded brass bolts, washers and nuts work out well for everything. Use what you can, but you should have a washer and a nut pinching down on everything.

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