[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: First light with 833 tube coil, then silence
Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
Hi all,
Well after a telephone troubleshooting session with Cameron Prince
tonight, we (mostly Cameron- he'd make a troubleshoot suggestion, I
would try it out and report the outcome) finally figured out why my
VTTC was getting no output. I had removed the lead from the staca-
to controller to one of the filament electrode pins of the tube and was
therefore operating without a filament ground. Once I reconnected
that, I was back in business ;^) I had even removed the 3 nFd mica
cap from the circuit and tried charging it directly from a HVDC source
to see if it vould hold any spark, all of this while on the phone with
Cameron. Of course the mica cap checked out fine in this fashion.
I got the stacatto controller better adjusted and now it's working
a lot better as well. I'm still only getting 10 to 12" swords with the
stacatto controller and about 8 to 10" sword like sparks operating
in continuous mode, both drawing between 15 and 20 amps at
about 110 to 115 volts input. I get the best output when I tap in
at the topmost (30th) turn of the primary, so that tells me that I'm
not able to tune it to a low enough frequency to resonante with the
secondary coil. The secondary coil is about 16.5" linear of #30
triple build magnet wire on a 3" PVC form. I think Steve Ward
(and Cameron) were using #28 with a 2 nFd (Cameron uses
2.4 nFd) wound on the same sized PVC pipe with about the
same winding length. So, I'm going to either need to get a bigger tank
cap or wind a bigger primary (I like the bigger cap idea better :^)
to get this thing tuned in properly. You can look at Cameron's
VTTC that he built on his website and that will give you a general
idea of the specs of mine. I will try to post a few pics for Cameron
to host on his Teslauniverse site after I get the "bugs" worked out
and I'm getting those 3 footers like Cameron ;^)))
David Rieben
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, September 23, 2006 11:44 PM
Subject: Re: First light with 833 tube coil, then silence
> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
>
> Hi Cameron, John G,
>
> I checked the output of both of mt MOTs and they were both good.
> I even checked to make sure that the MOT filter caps were taking on
> a good charge after powering up by shorting a srew driver blade across
> their terminals immediately after shutting down the power before the in-
> ternal bleeder resistors bled down the charge, possibly suspecting the
> diode had failed short circuit. The caps wouldn't always be left with a
> full charge immediately after shutting the power down since they won't
> always be shut down at the sine wave peak and in my case, they would
> be left with a full charge every time after shut down. Like I said
before,
> the main G3 tank cap makes absolutely no spark from shorting its 2
> terminal ends with the power applied. I did not try this before the
> output went to zero, but it stands to reason that this should reveal
> some visible discharge if the cap is putting out oscillations into the
> primary coil. Also, the primary coil now stays cold when I do turn
> it on, whereas it would get warm after running it a few minutes
> when there was an output, so it seems that no oscillations are getting
> to the primary coil
>
> Also, I think that my primary coil was a little short with its 30 turns
> coupled with my 2 nFd primary capacitance since the output kept
> getting a little better each time the I added more turns all the way
> up to the 30th and final turn, when it was working. May opt for
> a little bit primary cap, like 3 nFd, to make my current primary coil
> tune in better once I figure out what's wrong. I think the #30 AWG
> secondary coil is making it resonante at a lower-than-expected
> frequency compared to the one that Cameron built using #28 AWG
> wire.
>
> David
>
>
> ----- Original Message -----
> From: "Cameron B. Prince" <cplists@xxxxxxxxxx>
> To: "'Tesla list'" <tesla@xxxxxxxxxx>
> Cc: "'David Rieben'" <DRIEBEN@xxxxxxxxxxxxxxx>
> Sent: Saturday, September 23, 2006 8:28 PM
> Subject: RE: First light with 833 tube coil, then silence
>
>
> > Hi John,
> >
> > I'm am aware of and agree with your statements. However, this is a G3
mica
> > transmitting cap rated 12A @ 300kHz. The diode David is using is only
> rated
> > at 750mA and would normally go long before the cap would. I guess
stranger
> > things have happened, but I would certainly rule out every other
> possibility
> > before buying a new cap.
> >
> > This is the cap David is using:
> >
> > http://www.teslauniverse.com/images/vttc/DSC02483.JPG
> >
> > Notice it's almost as big as the tube...
> >
> > David is, if I'm not mistaken, running dual MOT's with the secondaries
in
> > series. I think it would be prudent to verify that one of those
> secondaries
> > hasn't opened and would consider this much more likely than cap, diode
or
> > tube failure.
> >
> > David, let us know what you find.
> >
> > Thanks,
> > Cameron
> >
> >
> > > -----Original Message-----
> > > From: Tesla list [mailto:tesla@xxxxxxxxxx]
> > > Sent: Saturday, September 23, 2006 7:49 PM
> > > To: tesla@xxxxxxxxxx
> > > Subject: Re: First light with 833 tube coil, then silence
> > >
> > > Original poster: "Dr. John W. Gudenas" <comsciprof@xxxxxxxxxxxxx>
> > >
> > > Cameron
> > > Be cautious with just voltage ratings on mica caps (or any caps for
> > > that matter).
> > > They need to handle high current too If the duty cycle is high, such
> > > as operating in self rectification without a staccato controller.
> > > The current in the tank circuit can get get up there. With my dual
> > > 833A VTTC which produces 24" corona without a staccato controller
> > > I can run for 10 to 15 minutes before things get hot. This coil
> > > destroyed at least three new 12,000 volt mica transmitting caps
> > > (typical ones about 3" x 2" x 4" with the screw terminals on top).
> > > One blew out the bottom and left a very unpleasant mess. I switched
> > > to very high current composite micas in an MMC arrangement.
> > > These are .0024 mfd. They are black cylinders about 3" in diameter
> > > and 5" long with large brass connectors on each end with 1/4 -20
bolts.
> > > The rating was 20kv too. I tried one and had very poor spark output,
> > > I saw this before cap failure. I put two in series then and
> > > paralleled this with another string of two in series.
> > > The coil worked great with no tank cap heating. The coil operates
> > > around 250 kHz. Cap problems ended completely. Good RF ceramics do a
> > > decent job too.
> > >
> > > Cap dielectrics tend to get quite lossy at high currents and voltages
> > > operating in the RF ranges. If they can't handle the current they
> > > die a rapid death.
> > > I have also destroyed MMC's with my DRSSTC that I didn't
> > > sufficiently design for long duty cycles. Not from over volting, but
> > > from too much current.
> > >
> > > Professors tend to get on soap boxes and preach, so today I am just
> > > saying consider voltage and current in capacitor choice (obviously
> > > dielectric too).
> > > David will solve his problem as intersecting all our responses, we
> > > suggested every component could be bad as well as wiring errors. Good
> > > luck David.
> > > Cheers!
> > > John
> > >
> > >
> > > On Sep 23, 2006, at 3:08 PM, Tesla list wrote:
> > >
> > > >Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>
> > > >
> > > >Hi David,
> > > >
> > > >I seriously doubt that mica cap is bad... They are built to handle
> > > >a lot
> > > >more than you are throwing at them with your VTTC. When I ran it on
> > > >mine it
> > > >stayed ambient temperature.
> > > >
> > > >Notice that 12kV rating is not peak or maximum, it's nominal and
> > > >you are
> > > >only at 50% of that with the VTTC.
> > > >
> > > >Cameron
> > > >
> > >
> > > Snip ---- Snip ---- Snip
> >
> >
>