Re: MMC caps: prices, sources, and types

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

At 07:05 PM 5/8/2004, you wrote:
>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.

If you have a lot of cash and need very high reliability, underrate 
them.  If you have little cash and can live with a failure in a few hundred 
hours, overrate them ;-))


>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... :( )

I do!  They sell tens of thousands of CD caps and their quantity discount 
is based on the "total".  Say 150,000 caps!!  When you sell a giant amount, 
they are happy to base the discounts an the totals instead on just one part 
number.

>Since you will certainly need more than 28 caps for a 1.5kVA power supply, 
>I'd say this is a viable option.

Geeks are cool folks, but when you need like two hundred, the price 
difference gets to be harsh.  Even Terry gets to be a "bad boy" and orders 
from Rell then :o)  But in low quantities, the Geeks are real cool and can 
help you with with questions.  Don't bother asking Rell how to make an MMC 
:o))))))


>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?

Yuck!!

Cheers

         Terry



>Good luck!
>
>Mark Broker
>Chief Engineer, The Geek Group