Re: MMC caps: prices, sources, and types

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

Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org> 

Michael,

Rating:  well, there are a myriad of opinions on this matter.  Some people 
run them horribly under-rated because they don't care if one fails - they 
just quickly replace it and move on.  Other's run them quite over-rated 
because their MMCs must survive extreme use and failure isn't an 
option.  Dr. Resonance (DC) builds Museum-class Tesla Coils that literally 
must last decades of hourly use without a failure.  He uses about 2.5x the 
"typical" rating on his MMCs and recommends to others to also do 
so.  People who do will almost certainly never have an MMC failure.  Most 
of the rest of us don't use our TCs daily, or even weekly, or don't mind 
the inconvenience of a failure.  There have been only a small handful of 
people, to the best of our knowledge, who have had MMC failures while using 
proper setup and protection (a safety gap) and an MMC built to the 
"recommended" specs on our website.  Since you seem hesitant to use the 
recommended ratings, I have to suggest that you incre!
ase the rating a bit, even if it's just to soothe your conscience.

Many people buy from Richardson Electroncics (RELL).  They have slightly 
lower prices, but a minimum order of 28 caps.  (I don't know why they get 
their caps for less than we do... :( )  Since you will certainly need more 
than 28 caps for a 1.5kVA power supply, I'd say this is a viable option.

With a 120BPS rotary spark gap you'll need somewhere between .025uF and 
.050uF, depending on ballasting.  For an NST, I would definately go for the 
higher number, but probably stay closer to the lower with a PT or MOT.

If the budget is tight, perhaps a bottle cap would be better?

Good luck!

Mark Broker
Chief Engineer, The Geek Group