Re: Good & Bad Maxwell Caps, MMC questions?

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

Original poster: "Steve White by way of Terry Fritz <twftesla-at-qwest-dot-net>" <slwhite-at-zeus.ia-dot-net>

>From what I have learned on the Maxwell web site and other sources, the caps
with the terminals on top are indeed low duty cycle. The lifetime is only
about 100,000 bangs. When your spark gap is running at 240 BPS or
thereabouts, you will use up its life in about 9 minutes. This doesn't even
account for how much life was used before you bought it used. I prefer the
Maxwell caps with side terminals (the PD series). The Maxwell web site says
that these have a life of at least 10,000,000 bangs and some range up to
100,000,000 bangs. There appears to be a continuous lot of these for sale on
E-Bay right now about every few days.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, July 16, 2001 10:16 AM
Subject: Good & Bad Maxwell Caps, MMC questions?


> Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<vanyo-at-echoes-dot-net>
>
> I just blew my Maxwell cap (0.06uF, 30kV, catalog #37321 - type with
> terminals on top).
>
> I was never sure whether this was a good cap for Tesla use.  I've seen
> guidelines in the past that said those with the terminals on top
> (instead of on opposite sides) generally didn't have a long life.  It
> worked great for a while, but now it's dead (cap makes a sort of
> fizzling sound when I first power up).
>
> Can anyone confirm that this is indeed not a good cap to use, or is this
> what I could expect with any Maxwell cap?  And if mine was bad, which
> are good?  The reason I'd like to get another Maxwell (if I can find a
> more reliable one) is that it's "plug-and-play" - no assembly required,
> and compact.
>
> Are MMC's really any better?  To what extent are they "self healing"?
> To build a really sturdy MMC with the geek group caps (942c), for use
> with 15/180 NST (three 15/60's), what is the minimum string length and
> number of strings to handle the voltage and current they'll see?  I can
> adjust upwards to get my desired capacitance, which is between 0.06uF
> and 0.045uF --- 0.06 because that's what I was using and it worked,
> 0.045 because that's the "right" LTR value for 15/180 with a static gap,
> but I don't know (I haven't calculated yet) if my primary has enough
> extra turns that I'd still be able to tap it in tune with 0.045 (I
> currently tap around 7.5 with my biggest topload, and have 10 turns).  I
> understand that the strings need to be of adequate length to handle the
> voltage (though I'm not sure what that length is to get a long MMC life
> with 15kV AC in tesla coil use).  Am I right that there is also some
> minimum number of strings needed for adequate current handling (180ma,
> in my case)?
>
> BTW (and I'm not sure, but I think I've heard this reported before), my
> coil seemed to be performing better than it ever had shortly before it
> died.
>
> Thanks,
> -  Bill Vanyo
>
>
>
>