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Re: Beginner's Tesla coil -First Light!

Tesla List wrote:
> 
> Original Poster: Terry Fritz <terryf-at-verinet-dot-com>
> 
> Hi All,
> 
>         10 inch arcs out of a GM HEI ignition coil!!
> 
>         I finally submerged the GM HEI coil in oil and let her go.  It
easily
> arced the 10" to a grounded salad bowl I was using to contain the mineral
> oil incase something leaked.  It probably could have gone further.  This
> was in single shot mode and the voltage should have been around 120kV.  The
> arcs were strong and blew a hole through a bit of PVC.  I added more oil to
> stop the "leak".
> 
>         The high voltage supply was loosing it's mind when the coil
fired, so I
> used a bridge rectifier and hooked it to my variac-neon charging circuit
> for my regular coil.  Thus I could fire it at a much higher rate than 1 BPS
> (I was getting carried away at this point).  I knew much more power was
> needed :-)).  The neon ran it right up there to ~10BPS.  Then the coil
> blew! :-(  The primary looks like a short now.  I'll clean it in detergent
> and do an autopsy tomorrow.
> 
>         The caps (17 0.1uF 630V Polypropylenes) worked very well and once
again
> showed they could very easily take Tesla abuse.  The simple spark gap was
> easily able to provide that function.  This coil only uses about 1/4 Joule
> of energy so it should not be strained.
> 
>         Of course, GM coils are not meant to put out 120kV or have 600
volt pulses
> applied to their 12 volt primaries.  This one was on a car engine for 16
> years so it may have been weak! :-)  At least the computer models and all
> were proven out.  I will get a new one and try again at a bit lower input
> power.  I got a little carried away when I saw those nice arcs.  I just
> kept pumping more and more power into it!  I probably would have given it
> the full 1kW! :-))
> 
>         If I can get this thing to hold together, it should make a very
nice,
> easy, and cheap beginner's coil.  With a new coil, I should be able to
> stress it out more carefully and find were it blows up and back off from
> there.  Today's tests suggest that it will still be a nice performer even
> at less than destructive output levels.
> 
> The science goes on....
> 
>         Terry

Terry:

	Two points.  First, I could never get more than about 3-1/2 inches
spark out of the coil, due to internal arcing even in oil.  Can 't tell
if your 10" sparks are directly from the coil or from a TC with the
primary capacitor charged from the coil, but if you got 10" directly out
of the coil you are very lucky.  Second, the insulation between the
inside of the secondary and the primary  will break down at a thousand
volts or so, so make sure not to exceed that voltage.  

	I am able to get 5"+ sparks from two coils (in oil) hooked in series
(low end of secondaries connected together and to the AC line through
600V MOV varistors in parallel with 4700 uufd 7 kV bypass capacitors. 
Primary is driven by a quadrac working from a voltage-doubling DC supply
directly connected to the line, and using resonant charging to get about
600 volts across the capacitor.  This is the same driver I have posted
here from time to time.

Ed