Re: Any Geekgroup MMC failures out there??

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi Luke,

Nope, no pics of that. I'll take the MMC to work tomorrow and snap a 
digital picture so I can upload it. I'll let you know.

Take care,
Bart

Tesla list wrote:

>Original poster: "Luke" <Bluu-at-cox-dot-net>
>You wouldn't happen to have a picture of your MC set up on the PVC would
>you?
>I haven't made mine yet and would like to see a new idea.  Maybe it will
>spark a thought.
>
>Luke Galyan
>Bluu-at-cox-dot-net
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Sunday, January 18, 2004 10:19 AM
>To: tesla-at-pupman-dot-com
>Subject: Re: Any Geekgroup MMC failures out there??
>
>Original poster: Bart Anderson <classi6-at-classictesla-dot-com>
>
>Hi Terry,
>
>Well, I've had one cap bite the bullet. This happened about a year ago.
>I
>was the 1st to receive caps from The Geek Group many moons ago. These
>are
>the 942C series 0.15uF caps. The one that that died was the cap next to
>one
>of the brass bolts I used for a connection. There's a hole in the cap
>about
>1/8" from the end. I don't believe it an arc from the bolt to the cap
>occurred since the hole is on the opposite side of the cap, however,
>something odd occurred. It was "not" from over volting the cap but I
>believe RMS current. I believe I was running 5 strings of 12 for
>0.0625uF
>total at the time. The caps were set on a pcb with 10M resistor soldered
>
>across the cap on the opposite side of the pcb. Each cap from side to
>side
>had at least 1/2" clearance. Plenty of room there. I suspect I exceeded
>the
>rms current capability (25 amps).
>
>I've since rebuilt the entire cap bank onto an 8" pvc tube. Each
>resistor
>is now soldered across the cap and each cap is simply placed on screws
>protruding from the pvc tube (this way I can maneuver cap arrangements
>anyway I like). It is currently 3 strings of 18 caps for a total C of
>0.025uF. I haven't had a failure since.
>
>I'm not sure why the cap failed. It's still on the pcb board along with
>5
>neighboring caps. I just threw it up in a cabinet and left it there ever
>since.
>
>Take care,
>Bart
>
>Tesla list wrote:
>
> >Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
> >
> >Hi,
> >
> >I was just wonder if anyone had any failures of Geek group caps for "no
>
> >good reason"?  I have not heard of any problems, but it seems like a
>good
> >time to ping the users out there to see if any problems have been
> >noted.  Sort of just checking to see if there are any holes or unknown
> >problems we need to check into.  Of course, if one does not follow the
> >tips or runs them out of what is recommended, that is your problem
> >;-))  But if you think you did everything right and they blew, I would
> >like to hear about it to see if any common trends or problems are out
> >there we don't know about that need fixing
> >
> >Perhaps additions to the "tips" too.
> >
> >
> >Cheers,
> >
> >         Terry
> >
> >
> >At 12:15 AM 1/17/2004, you wrote:
> >
> >>Well, let's put it this way....  We have never heard of a failure of a
>
> >>"Geek Cap" that wasn't directly related to poor design or
> >>construction....  The design chart on our mmc page is tried and true.
>If
> >>you build an MMC using the suggested design on our site and follow our
>
> >>construction guidelines, your MMC should last forever in hobbyist
>duty.
> >>
> >>If you really do feel uncomfortable using an "underated" capacitor,
>then
> >>go ahead and make it more beefy. :)  But, IMO, if "our" caps can hold
>off
> >>5000V, one could argue that 10 in series is plenty overdesigned.  IIR,
>a
> >>second high voltage test with a newer cap held off 5300V at the first
> >>breakdown, then more than 6000V at the second (that's a 2.7J bang
>inside
> >>the cap!).  Then the current draw got pretty high.  You have that info
>
> >>handy, Terry, or do I have to go digging?  (one of these days we'll
>just
> >>add that piece of information to our site)
> >>
> >>http://www.thegeekgroup-dot-org/mmc/
> >>
> >>FWIW, my first MMC was made from 1600V Panasonics (I think I managed
>to
> >>hit Terry's first bulk buy in early 2000), total voltage rating of
> >>19.2kV.  After a few hours of runtime, one dead NST, one dead "Terry
> >>Filter" (shorted the MOVs), a lot of toasted AOL CDs, and a lot of
>awed
> >>spectators, the MMC caps are still fine.  And IMO I've been gentle on
> >>those compared to some of the torture we've put our Geek Group MMCs
> >>through!  The Geek Group MMCs have seen many coil setups and many
>power
> >>levels, including running near-resonant value caps with a 14.4kV PDT
> >>overvolted to ~280V input on a 360BPS SRSG coil (half the Gemini
>project)
> >>and also running a static gap 12/180 setup with no topload (we tuned
>at
> >>about 2 turns - the gap was much less happy than the MMC).  So all
>this
> >>is just saying that, yeah, these are pretty tough little buggers.
> >>
> >>Cheers
> >>
> >>Mark Broker
> >>Chief Engineer, The Geek Group
> >
> >
> >
> >
> >
>
>
>
>