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Re: Maxwell 37667 dies interestingly...thoughts?
Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
(sorry for the spam)
I just turned up a prior thread on this and I'm going
to assume that what we were doing here was "bad"
because of the "voltage reversal" thing (the 37667 is
apparently only rated for 50% reversal), so we were
pushing it hard in that respect desite it's otherwise
Probably time to go and buy a bunch of CDE 942s,
resistors, and lexan...sigh... :-)
--- Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "J. Aaron Holmes"
> Should have added a few more primary details:
> Supply is a 14.7kV pole transformer. Peak primary
> current would have been around 250A. Gap is async
> rotary. Estimated break rate: About 400 bps.
> seemed (sounded) consistent, though admittedly
> adjustment of the gap had been performed, so it may
> have been a contributing factor in the Maxwell's
> demise. I'm not sure.
> --- "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
> > I took my Maxwell 37667 to a friend's place over
> > weekend to see if it would help get his new 24"
> > to put out some sparks. Despite early
> > that things were too far from complete to run the
> > thing, we got enough wire stripped quickly enough
> > do a temporary lash-up before daylight failed.
> > Things kicked off with the destruction of two
> > homemade
> > rolled caps that he'd spent a bunch of time on.
> > What
> > a bummer (and boy did they look cool, too!). I
> > a
> > deep breath and offered to put the Maxwell on the
> > cooker to see what would happen. We were
> > immediately
> > gratified with 8- and 10-foot streamers as the
> > rate topped 400 bps. Yikes! We dropped a few
> > different toploads on the thing and played around
> > for
> > a while. In the end, the Maxwell probably had
> > two minutes of runtime spread over a ten-minute
> > period.
> > Then, Bad Thing #1 happened: A streamer hit the
> > wire
> > between the Maxwell and the primary. Due to the
> > temporary nature of the wiring, the cap had been
> > sitting relatively exposed a few feet from the
> > of
> > the coil. Doh! A metal sawhorse was quickly
> > over it.
> > And finally, Bad Thing #2: Shortly into the run
> > immediately following placement of the sawhorse,
> > crack opened in the Maxwell, and the oil drained
> > rather quickly, leaving a nice puddle of Maxwell
> > juice
> > on the floor (VEERRRYY slippery stuff, I can now
> > say!)
> > What is quite interesting about all of this is
> > due to the surpise of seeing the Maxwell croak,
> > took us a few seconds to kill the power. In
> > few
> > seconds, the coil continued to operate normally;
> > there
> > was no obvious dip in performance. The contents
> > the Maxwell were quite warm, though not what I'd
> > call
> > "hot", and I neither saw nor smelled any sign of
> > burning. On top of that, measurement revealed
> > the capacitance was still 0.03uF, and no DC
> > resistance
> > would register on the DMM.
> > So the mode of failure here is a little unclear
> > me.
> > Did thermal expansion of the contents simply pop
> > the
> > case, or was there most likely some kind of
> > fault, perhaps initiated or encouraged by the
> > in the prior run?
> > As the Maxwell's guts seemed in remarkable shape,
> > friend is going to try running them in a bucket
> > mineral oil and see what happens. I'll report
> > with the results. If they aren't serviceable,
> > perhaps we'll pry them apart even more and see
> > we
> > find. They were just too pretty not to get a
> > chance :-)
> > Any other thoughts on "Why Maxwells Fail"? I
> > even felt the thing get warm in my little coil
> > running
> > at 120 bps.
> > Regards,
> > Aaron, N7OE