Re: Failure mode of MMC's

["sundog" <sundog-at-timeship-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Terry, All..

Good news!  I tore down my MMC to individual strings,and came up
around 5.2nf(5.0-5.2 range) for each.  So my MMC is good.  The caps
look good, no cracks, no blistering, no nothing.  I am running the
7 strings of 11 the MMC Calc suggested (woohoo!), so tomorrow I
look at the trannies for dead legs (which I suspect after a bit of
testing this afternoon, 'cause a set of 2 of 'em gave *no* output
on the gap at all.  No buzz, no nothing, so I think I gots a few
dead trannies.

  I hang my head low, as I wasn't using a saftey gap on this (never
used one on a static gap system, and didn't have the spare
electrodes to use on a sync gap), but I've learned the error of my
ways.  I'll be assembling a saftey gap for the sync gap...Flame me
not...The good thing...The trannies that are good will be put to
good use!  I was going to re-wire the whole lot of 'em anyway on
the HV side.  So I'll be sure to post what happened.  I'm strongly
suspecting a dead tranny or two now...But!  Not a huge deal, as I
probably have found the  PT's I've so desparately sought. I'll post
more on that when I get the info from the guy selling them..

On those, I'll aim for scrap prices ($1 per kva), and offer the
ones I don't use to the list.  I can't promise, as I am paying for
surgery and a slew of other things right now, but if I can, I'll
offer them at what I paid, plus shipping.  "Share and enjoy!", is
the motto for that.  I believe there's 4 up for sale, so I'll try
for all 4 if I can.  Again, no promises, but I'll do my best.

Back on track now...The MMC's have performed admirably!  A standing
ovation to Terry for his work on the MMC front!  We all salute you
for providing us medium-grade-guys a cheap and super-good tank cap
for the buck!  Kudos and a standing ovation to the guys who handle
the bulk buys! (Dave, Terry, others!), who make the MMC affordable
for the masses...we all drool over the Maxwell and Plastic
Capacitors caps..., but can't justify the cost for a "hobby."  take
a bow, guys, you deserve it!

Tomorrow brings more work, and lots to do.  Till then, keep it
sparkin', and keep it safe!

Shad

-----Original Message-----
From: Tesla list <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Friday, August 11, 2000 11:04 PM
Subject: Re: Failure mode of MMC's


>Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>Hi Sundog,
>
>The numbers for your set up are:
>===========================
>MMC Calculator  Ver. 2.1  2/19/2000  Terry Fritz
>Transformer voltage =  12000
>Transformer current =  .18
>Firing voltage =  16970.52
>Fo =  250000
>Break rate =  120
>Cap value =  5.6E-08
>
>Strings  Caps/Str  Capacitance  Voltage   Temp C    Cost
>  3        5         33.60         8000    19.75   21.75
((  :-(  
>  5        8         35.00        12800     7.71   58.00  :-((  :-)  
>  6       10         33.60        16000     4.94   87.00  :-|   :-)) 
>  7       11         35.64        17600     4.08  111.65  :-))  :-)) 
>--------------------------------------------------------------------
>  8       13         34.46        20800     2.92  150.80  :-))  :-)) 
>  9       14         36.00        22400     2.52  182.70  :-))  :-)) 
>=====================================
>
>so if your using an MMC larger than 5 x 8 caps (I assume your are using
>Panasonic) you cap should be fine.
>
>If they over volt, they either recover or blow the case.  Over current may
>melt them down internally but the case should still cook as they short.  If
>one has failed, you can rip it open to see if it was explosive (over
>voltage) or melted (over current) damage.
>
{snipperz!)