RE: defective caps?!?!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mccauley, Daniel H by way of Terry Fritz <twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>



Actually sounds like your caps were run when the coil was out of tune.  This
happened to my 42L series GE caps (2000V, .33uF) types when i first ran my
coil.  I burnt up two also that way.  But once the thing was in tune, no
more problems and the caps barely get warm even have 5-10 minute runs at
15kV, 60mA.

Dan





I now have a very sick feeling in my stomach,

I may have bought about $120 worth of bad caps!  While my GE 42l series 
3000v caps have lasted for a looooong time, the 42l 1200v caps may not!  I 
may send one to Terry so he can check it out.  Heres the story.

I just finished up a medium coil powered by a 12/60 and a static gap.  My 
MMC is 20 in series of 1200v .33uf caps for .0165uf -at- 24kv.  Well the coils 
performance was poor to say the least with only 2 foot arcs.  So i tried and

tried with no luck.  So just out of curiosity, i felt the caps after i 
turned it off.  They were hot!  well 2 of them were.  I let them cool off, 
then ran it again.  Checked for heating, it was still in those 2 caps.  One 
was hotter than the other.  So i took them out.  I took apart the really 
warm one and found some depressing realizations.  The ends of the foil were 
totally burnt to a crisp at one end!

Here is where the sick feeling really sets in.  The 20 caps didnt cost 120 
bucks, but the caps for my large coil, and small coil did!  Now it gets even

worse!  This is just speculation, but i think the large caps on my large 
coil are going bad!  Last time i ran the beast, i had some trouble getting 
it to tune.  I did get the normal 5 footers, but i had lots of trouble 
getting there.  I did check the temp on these caps the first night i ran it,

and there were no signs of heat, but i didnt feel each cap individually, nor

did i check it after the first night.  So i am praying that these caps are 
better because my current bank cost about 85 dollars.  I was starting to 
feel confident in these caps.  I just upgraded to 2 strings of caps on my 
big coil, but never ran it yet.  Each string is 24 X .68uf -at- 1200v for a 
,0283uf -at- 28.8kv.  By the way, is a .0566uf cap too big for a 15/120 system 
with no RSG, but a blower gap?  I like the idea of that huge cap for some 
huge current handling, unless these are "crap caps" and they will all fail 
soon anyway.

Terry, is there a way for me to send you a cap so you can test them and find

any problems they may have?  Im not positive that the whole series of 42l 
caps are bad, so i want you to look at them.  Im really hoping that this was

just a defective cap, and that the rest will be ok.  The surprising thing is

that, i could charge the cap to at least 1500v with a small HVDC supply, and

it made a fat spark.  But i did hear some clicking noises when it was 
charging.  So lets hope that maybe it is just a defective cap, or at least 
its only this specific model thats bad.

Steve Ward.


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