Re: 811 tube coil

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

Original poster: "James by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mustang3-at-cox-dot-net>

Hi Steve, list
    Looks like your VTTC is working pretty good. The only thing you have to
watch for is the toob getting too hot. The amount of current drawn is not
too important. If your plate cap is getting warm....this is not a good sign.
You prolly need to add a string or two to reduce the current. The MMC's can
easily be over-currented by a VTTC. Add a few caps to each string(reduce
value) and a few more strings. If you have an O'scope, you might monitor the
grid while doing your tuning. The number of winds on the tickler coil is
part of the tuning process. As is the value of the grid leak (resistor &
cap).
    On my VTTC I have a 5000 volt negative pulse on the grid. Turns the toob
off hard. If I remember, 811's need 300-500 volts for turn off(1500 plate
voltage). I use a different schematic for my toob coils. I got it out of an
electronics mag. in the late 50's. If you have that copy of "Science
Expermenter". Was on the list somewhere. This is almost the same circuit.
    I think you need a mica cap (or a good MMC) for the tank cap. I don't
think the rest are very critical.

Later,

James
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, July 01, 2002 6:04 PM
Subject: Re: 811 tube coil


> Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<srward16-at-hotmail-dot-com>
>
> Hi,
>
> I have a question that somewhat relates to the post but just a general
> question about operation.  Sometimes when tuning, i cannot get any sparks
to
> breakout, unless i bring a screwdriver very close.  When this happens, the
> Amp meter says its pulling 6A which means that the tube is running at its
> max.  Is this dangerous to the tube?  I try to prevent this as much as i
can
> but it seemed to happen alot today.  Also a very opposite situation is
that
> ive managed(or so i think) to achieve the best tuning with my tuning cap.
I
> get current draw of less than 3A, and i get a good 2.75" arc.  Does this
> sound like im getting close to having the best tuning with my current cap?
> Im also wondering about my cap, it gets very warm(actually hot).  Its a
> small MMC of poly caps.  Total for the bank is 900pf at 8kv.  Im supposed
to
> have a 1000pf cap at 10kv, its also supposed to be doorknob type.  Would a
> doorknob really work any better?  If so, where could i get one.  I want
one
> of the best caps i can get(for cheap) because my performance seems to be
> highly relying upon this cap.
>
> Steve Ward.
>
>
> >From: "Tesla list" <tesla-at-pupman-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: 811 tube coil
> >Date: Mon, 01 Jul 2002 12:37:06 -0600
> >
> >Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> ><FutureT-at-aol-dot-com>
> >
> >In a message dated 7/1/02 10:04:35 AM Eastern Daylight Time,
> >tesla-at-pupman-dot-com
> >writes:
> >
> >Hi Steve,
> >
> >I was obtaining about 17" sparks at the time of my sputter
> >mode experiments.  The sparks were dimmer and a little shorter
> >than in the true staccato mode.  Also, some kickback may occur
> >in the sputter mode, which may destroy tubes and capacitors,
> >if they are running near their breakdown limits.  Others have
> >also reported to me that their sputter mode sparks were a little
> >shorter than their true staccato sparks.  At the time, I was
> >using about 4 times the rated max plate voltage on the tubes,
> >so it's not surprising that they failed occasionally in the sputter
> >mode, but they survived in the true staccato mode.  I didn't
> >really do many sputter mode tests after the initial work.
> >Changes in the grid leak C vs R values may be helpful/
> >detrimental to the overall performance to some degree.
> >
> >Cheers,
> >John
> >
> >
> > >
> > > Hi John,
> > >
> > > What are any of the negetive effects of sputter mode?  Ive gotten my
> >coil to
> > > work much better since i last posted on the list.  Im at about 2.75"
> >arcs
> > > and nothing is really going wrong(exept no 6" spark yet).  I do notice
> >the
> > > frequency changing alot when i play with the arcs.  If you could tell
me
> >a
> > > little more about this type of operation that would be helpful as im
> >still
> > > trying mew ideas with this coil.
> > >
> > > Steve Ward.
> > >
> > >