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LTR MMC Question - "Geek Group" caps



Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-uswest-dot-net>" <vanyo-at-echoes-dot-net>

OK, so I think I'll go with MMC for my under-construction first coil,
and am considering the Cornell-Dubilier 942C (aka  "Geek Group") caps
(0.1uF or 0.15uF, 2000Vdc) for their high capacitance to cost ratio, but
I'm having trouble figuring out the string length (caps in series) and
how many strings I need.  Ideally, I'd like to be able to run with
either two or three 15/60 NST's, and want to use an LTR cap size, so I
think I need to be able to get 0.03uF and 0.045uF from the MMC.

Question 1: How critical is the exact cap value when using an LTR cap? 
For instance, can I use 0.05 with three 15/60's?

Question 2: How many strings, minimum, do I need, for adequate current
handling (with three 15/60 NST's, for instance)?  I remember reading
more strings is better, but with these caps, more strings quickly means
much longer strings just to keep the capacitance *down* to where you
want it, and it gets costly again.

Anyway, here are some of the options I was considering:

A) Using 0.15uF caps, 3 strings of 10.  
   2 strings = 0.03uF, 3 strings = 0.045uF.
   Quite cheap, but seems pushing it voltage (20KVdc) and current (?)
wise.

B) Using 0.15uF caps, 5 strings of 15.
   3 strings = 0.03uF, 5 strings = 0.05uF.
   30KVdc seems quite adequate.  Will 5 strings handle the current with
three 15/60 NST's?  
   And will 0.05uF be a good LTR size for three 15/60's?

C) Using 0.01 caps, 6 strings of 13.
   4 strings =  0.030uF, 6 strings = 0.46uF
   26KVdc - adequate?, less than $150 - not too bad, good match to the
capacitances I think I need.

Any thoughts?  This (the cap) is the only item I have left to purchase,
and having made the mistake of buying a batch of 940C's in the past
(before I found this list), I want to be careful this time.

	Thanks,
	Bill Vanyo (who feels he's being a pest with all the many questions,
but is very anxious to get his first coil running)