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Re:Nate's Probs: Information

Hi Nathan,

	Sounds like your 1000 ohm problem is taken care of.  I would get rid of
all the alligator clip connections especially in the primary circuit.  The
primary will see hundreds of amps and the tiny contact area of alligator
clips will not handle that current without a lot of resistance.  An ohm
meter will read fine but when you pump 400 amps through those connections
they will have very high loss.  Solder or bolt down those connections like
you were going to weld a bumper onto a car with the current (I guess cars
have plastic bumpers nowadays but you see what I mean ;-))).

The best part follows...

At 05:28 PM 01/05/2000 -0800, you wrote:
snip....
>I have been ohming around on the toroid, and just found one problem.  I had 
>been connecting my secondary ground with an alligator clip to a galvanized 
>nail to which my 3/16" grounding copper wire was attached. THAT was a huge 
>source of resistance.
>
>Also, one interesting thing: I am using real foil tape, (the stickiest stuff 
>I have ever run into besides TYVEK tape) and am testing different amounts of 
>resistance between seperate pieces on the toroid!
>
>Most of the pieces have good continuity to the connection point on the 
>toroid, and the bottom of the secondary where the ground is connected. But 
>some of them have about 4-500 ohms of resistance.
>Otherwise, though, I think I have pretty good continuity now.
>
>One special thing: The way I have my secondary grounded is the wire I wound 
>it with comes through the bottom of the form through its mounting board, and 
>attaches with an alligator clip to the grounded copper wire.  Is that OK?
>
>
>>
>>additive).  This is starting so sound a lot like there is something really
>>wrong with the primary cap.  I assume the wires connecting the primary
>>circuit are reasonably heavy and you have ohmed around in that circuit to
>>be sure there are no high resistance connections.  It does not take much
>>resistance in the primary to kill a coil's performance.  However, a bad
>>connection should have flamed out...
>
>My connection wires are probably all around 14-18 guage wire.  They all have 
>alligator clips, and it seems to be good continuity all around the primary 
>circuit.

Thicker wire would be nice but what you have will do for now.  Get rid of
the alligator clips....

>
>The capacitors I have running the coil are as follows:
>
>I have two rolled caps each tested with an LCR to 0.011uF.  They are both in 
>two inch PVC pipes, and are constructed with: four layers of 6 mil black 


""BLACK""!!!!!!!!!  Aaarrruuuggghhhaaaa!!!!  That plastic is made for
outdoor use.  It is made to resist the effects of ultraviolet rays from the
sun.  They make it black by adding CARBON to it!!!  Carbon is resistive and
the same stuff common electronic resistors are made from.  99% chance that
black stuff is partially shorting your caps and dissipating all the power.
At low voltage, your EXCELLENT oil probably makes them look like great
caps.  However, under high voltage stress, they are just big resistors in
parallel with the capacitance.  Perhaps some plastics experts can confirm
this, but that black plastic crap should be a disaster in TC cap service
and would totally explain your coil's problems.  This plastic probably
would not blow or arc but only quietly "drain" massive amounts of energy
from your coil...


>polyethylene sheeting, then a layer of Al foil.  Then four more layers of 
>poly, then another of Al foil.  The poly sheets are 12" by 36" and the Al is 
>8" by 32" so I have 2" clearence all around.
>
>The other cap, I built to be 0.0053 uF. I never got it tested, but just 
>found out about a new resource that has an LCR I could probably use.  It is 
>at the radio shop at my dad's power company's warehouse.
>
>Anyway, it is a plate cap.  It is made of the same black LDPE sheeting that 
>the rolled caps are. I built it to 5.3nF, but am not sure anymore how many 
snip.....
>
>>You are really getting close to the problem.  A 2 string 20 cap MMC (10nF)
>>would cost about $35 with Panasonic caps and that is really the worst thing
>>it could be at this point.
>
>I have been wanting to build a MMC, but don't know where to get the caps.  
>What types of caps are these Panasonic ones, and where can I get them? I had 
>never seen an MMC for that cheap before! This seems like a viable option 
>now! wow!

Clear polypropylene is the plastic of choice rather than the black junk but...

I have a few hundred caps laying around...  If you put 11 in a row (0.056uF
at 1600 volts) you get 5.09nF at 17600 volts rated which would make a nice
EMMC for your coil.  22 caps (two rows) would give 10.18nF.  I sell them
for my cost at $1.40 each (I buy them by the thousand).  If you want, I can
get you the 22 caps, a board, 10Meg resistors and a few brass bolts for 40
bucks which includes shipping.  I am running low so I am not actively
"trying" to sell them these days but your's is a "special" TCML case ;-)
Others may have better deals...  If interested write me off list and I'll
get the stuff sent to you ASAP so we can see if this solves this illusive
problem...  If the money is too much, I'll "loan" you the darn thing just
to see if it solves this problem...

>
>>If things really get bad, we can see if there are any other coilers near
>>your area that could come and check it all out.  Sometime another set of
>>eyes that have "seen it all before" can quickly figure things like this 
>>out.
>
>I am located in Newport, Oregon, and would be delighted if any coiler out 
>there that was near me would contact me!  e-mail me if you think that would 
>be possible.

I think another coiler would have picked up the black plastic thing
instantly where we in "e-mail land" had to search a few days...  Without
actually "being there", such things are rather hard to pin down...

>
>Thanks very much, Terry.  I think we are close now too!

Yeah, I think that black polyethylene plastic is definitely the killer.
They use it under rocks and bark to keep weeds down...  A soft limp greasy
carbon impregnated stuff...

Since your coil is so well constructed, with a nice sync gap and all, you
should be using MMCs anyway just to keep up with modern times ;-)  This is
great!  Your coil seems to be a super great design so it should really run
like the wind once the caps are fixed!!!  

This has been a great example of how to trouble shoot a coil that is not
working.  You had all the data to find that it was in tune and you could
provide the critical dimensions and such that all of our fancy programs
needed to get the vital technical details.  We were able to eliminate many
other possibilities and begin focusing on the primary cap.  Once there, we
have fairly quickly found what "should" be the big problem and the solution
is obvious.  Hopefully, an MMC will allow your coil to very quickly reach
the performance it should have.  So...., that musty old neon was worth
blowing up just for mental therapy ;-)))

Cheers,

	Terry
	terrellf-at-uswest-dot-net

BTW - Your coil's output impedance is 130k ohms and the arc load is 280k
ohms...  Such analysis is still in development but your coil is similar to
many that work just fine in this regard.  The research continues...  The
#20 wire is fine too....