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Re: Here are my current specks: Was I give up!
Ok, this circuit is not the classic tesla coil design. believe me when I
tell you my description is accurate. It just goes to show there's more than
one circuit for a spark gap tesla coil. Actually till it fried, I was
actually proud of having a tesla coil with a different design. I really
badly need some solid way to prevent NST burn outs like this. I used to do
coils before but when three NSTs fried in one month with the last one
lasting five seconds, it was disgusting enough for me to give up trying for
over twenty years!!
Just to make sure you understand let me try to do this graphically
V-------Cap 1
----------------------------------|------------------------------
---|I|I|I||I|I|I------------------------()()()()()
/ |
()
NST <----- high voltage out. Z <----- Spark gap
() <----- Primary of tesla coil
\____________________|__________________I|I|I|I||I|I|
()
^____Cap 2______()()()()()
The secondary is naturally next to the primary coil but is not shown.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, August 22, 2000 8:27 PM
Subject: Re: Here are my current specks: Was I give up!
> Original poster: Parpp807-at-aol-dot-com
>
> In a message dated 8/22/00 2:11:57 PM Central Daylight Time,
tesla-at-pupman-dot-com
> writes:
>
> << Subj: Here are my current specks: Was I give up!
>
> Original poster: "Garry F." <garryfre-at-pacbell-dot-net>
>
> Garry,
> My comments are all IMHO. Also, I have built a successful bipolar coil but
> never a 1/4-wave coil
> of your configuration: BUYER BEWARE.
>
> lots of snips
> >>As I mentioned before, I built it according to plans from
sciencefirst-dot-com
> but it did not work as advertized (Oh what a surprise).<<
>
> I have never heard anything good said of this outfit
>
> >>NST is the same in all cases 9,000 volt at 30 MilliAmps<<
>
> At only 270 Watts I don't think you need the line chokes. Let's get things
> simple.
>
> >>Given this NST, I caculate the Impedance as being 300,000 ohms<<
>
> >> I caculate that I need an .088pf capacitor or since I have two in
series,
> I will need two about
> 176uf each.<<
>
> Uh Uh. A pico is 10 EE-12. You write 8.8 EE - 14 uF. Do you mean 0.0088
uF
> equal to 8.8 EE-9 uF?
I am sorry, I don't have a clue how to answer this at all. I guess I mean
.0088 uf between the two series caps.
>
> C = 1/ 2pi x 60 x 300,000 Ohms = 0.0088 uF. I would use a 0.01 uf MMC.
>
> >> My current caps are aluminum flashing stacked<<
>
> I know nothing of one of these contraptions. To me, they are unreliable
and
> dangerous. I would toss the aluminum plates into my toy box and build a
nice
> MMC. Someone else will probably have a
> more constructive and tactful opinion. :-))
>
Hmmm, I keep hearing about MMC but have yet to see any plans for one. I
don't know even know what MMC stands for. I probably should be in the
beginning
tesla coil mailing group but all I got was a reply that they needed my full
name and so I replied and gave the info expected but I've not heard a thing
since.
> I think you wrote that you are using Brent Turner's book.
> Please refer to the BASIC TESLA COIL SCHEMATIC on page 58.
>
> >> The caps are in series with the primary winding and the other
> end goes to one side of
> the spark gaps. This isolates the primary from the rest of the circuit as
> far as the 60 cycle current
> is concerned. The primary is center tapped in the center after tuning
> through a third choke with the
> same configuration as the other two.<<
>
> Garry, this paragraph is totally confusing and has no resemblance to the
> schematic on page 58
> of Turner's book.
That's correct, it does not resemble Turners book because I built the thing
from plans from www.sciencefirst-dot-com and I did not have Turner's book yet.
>
> I can assume that you really mean the HV primary consisting of the
capacitor,
> the SG, and the
> 40 turns of # 14 wire which are connected to the HV secondary of your NST.
> Your description places everything on the LV 120 V primary side of the
NST. I
> do not think this is what you intended
> to say. Your description gets totally out of control when you describe the
> caps (more than one)? being in series with the primary winding and the
other
> end goes to one side of the spark gaps (more than one)?
Not out of control at all, just factual.
>
> >> Finally, I tried two brass doorknobs. Flat surface area inside the
same
> PVC
> joint with the same fan.
> Result was a significant improvement in performance to the tune of 16"
> sparks. The best yet!!<<
>
> This is not bad, actually it is very promising because things are probably
> not as bad as your
> description infers.
>
Well, I found out that the brand new NST is fried. I tried finding one
locally but nobody wants to do business with walk-in's here except to charge
$109 for a new
NST. I can't even buy wire from any of the motor repair shops tho spools of
wire are sticking out the wazoo there.
> >> The next morning, I turned it on and the gap would only fire
sporatically.
> So, I closed the gap a bit
> and by the time I got some reliable firing the sparks were quite a bit
> weaker. They were thinner and
> much shorter, with less bang and noise from the toroid.<<
>
> I get the vibes that your capacitor is not taking an adequate charge.
>
I had a feeling it was bleeding off the charge but as you can see it was
really the NST
> You can very carefully test your NST by first making sure the power is
OFF.
> Connect one end of a
> piece of HV lead to one terminal of the NST, strip the other end and tape
the
> wire to a long (12-inch)
> piece of wood. Do not touch the wire. With the power ON, bring the end of
the
> wire to the NST
> case. You should be able to draw out 1.5 to 2 inches of bright juicy arc.
If
> this works for both
> terminals the NST is good.
>
It's good and fried and in the process of depotting and I hope revival.
Otherwise it could be about six months before I got enough money for
another.
> >> I am most impressed with the kind and never harsh
> replies I got from this
> group. You should all be proud.<<
>
> Yes, the Tesla group is the greatest. I again urge you to
study-study-study,
> and ask plenty of questions. No flaming on these pages.
>
> Hope some of this helps. Also hope I got some of it right. :-))
>
> Happy day,
> Ralph Zekelman
>
>
Thank you kindly.
>
>
>
>
>
>