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Re: [TCML] First TC firing

Matt,
Dielectric puncture simply put is when your cap dies because voltage ate a hole in the dielectric (in this case soda bottles.) I am 90% positive that is why your spark gap will not fire, I say this with such confidence because a few months ago I did an experiment with soda bottle caps and found their life expectancy with 2 MOTs (only 4000 V) was about 10 seconds. With two in series they lasted about 30 seconds continuous. If you cannot afford real caps, make some out of glass for now, they do not deserve much of the bad rap they have been given, in OBIT service they have served me for 4 years and never failed (short runs of course, 2 minutes tops.) Once you get your gap working then you can try to fix the tuning. One more thing, put your spark gap parallel to the OBIT, and your cap in series with the primary, this is much better for your transformer. Good luck. 

Scott Bogard.

Matt wrote:

Thanks for all feedback, it has been very helpful.

Spark gap does not fire - I've had the gap practically closed and still no
response. I'm pretty sure the wiring is fine - I checked it many times, and
even when I wired it with the caps in parallel with the spark gap on their
own there was still no spark. I'm not quite sure what you mean by a
dielectric puncture - I will have to look it up but I suspect this may be
very likely as the caps were pretty makeshift. As I've said - the spark gap
if definitely not too wide.

The OBIT still works though - I set up a quick jacobs ladder to make sure
and it works fine.

On top of that I do probably need to have done my calculations a lot better.
Will the fact that my wire for the primary is enameled pretty thickly affect
it adversely?

-Matt

On Wed, Dec 10, 2008 at 1:36 PM, Lau, Gary <Gary.Lau@xxxxxx> wrote:


A plastic bottle cap with a dielectric puncture WOULD render the coil
completely non-functional.

Does the spark gap fire?  If it does not fire, the possible causes are 1)
dead OBIT, 2) wiring error, 3) shorted cap (dielectric puncture), 4)
too-wide gap.

If the gap does fire, it's likely that the primary/secondary tuning is way
off.  How do you know that you are correctly tuned?  One cannot simply wind
a bunch of heavy wire for the primary, make a cap out of whatever bottles
are available, wind a bunch more thinner wire for the secondary, put an
arbitrary lump of metal on top for a top load, and expect the primary and
secondary frequencies to match.

Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Matt
Sent: Wednesday, December 10, 2008 3:14 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] First TC firing

I am aware the coke bottles will not last long (temporary measure for the
moment). However at the moment the coil is completely non-functional.

Does

anyone have any ideas where I'm going wrong?

Here's an ASCii diagram of my current layout;

                                O--o--O
                                   (
                                   (
|---------|-------|-----o o-----|  (
|         |       |     SG      |  (
|         |       -             |  (
OBIT      GAP     CAP           )  (
|         |       -             )  (
|         |       |          L1 )  ( L2
|---------|-------|-------------|  |
                                  RF
                                  GND

On Wed, Dec 10, 2008 at 3:35 AM, Lau, Gary <Gary.Lau@xxxxxx> wrote:


The amount of RF that your xfmr is exposed to is less if you swap the
positions of your main gap and the cap.  Performance is the same, but
placing the main gap across the xfmr effectively shorts out most of the

RF

energy from going back to the xfmr.

If you are using plastic coke bottles, they're not likely to last very

long

:-(

You give no specifics (a few turns, don't know exact gauge, vague

copper

vase topload...)  that would allow one to calculate if you are properly
tuned, so I'll leave that to you.

Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Matt
Sent: Tuesday, December 09, 2008 4:21 PM
To: Coil Mailing List
Subject: [TCML] First TC firing

Hello everyone, thanks for your help so far.

I am about to test my coil and would like some input to make sure

things

won't go drastically wrong.

I have my transformer (2x 7.5kv outputs at 40ma Danfoss OBIT) wired

to

the

mains. From there it is wired in parallel to first my safety gap,

then my

capacitor bank (two 2l coke bottles, wrapped in foil and filled with

water

saturated with table salt). In series to that I have my spark gap,

and

then

my primary coil (a few turns of thick  enamelled wire)

The primary is at the base of the secondary (1000+ turns of very thin

magnet

wire - I don't know the exact gauge, but it was the second thinnest I

could

get from Maplins, and is thin enough to snap under force applied by

me).

The

secondary is grounded to a square sheet of chicken wire, and the

topload

is

the bottom of a copper vase.

I include a VERY simple circuit diagram.

Some feedback would be MUCH appreciated soon as I am about to turn it

on

and

could do with some reassurance that I'm not going to destroy

something...

Thanks a lot,

Matt

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