Re: [TCML] Is this 2,3kW Triode suitable for a VTTC?

[Steve Ward <steve.ward@xxxxxxxxx>]

The peak input voltage is 2X as high (ideally) with a doubler (why else call
it a doubler?).

Steve

On Sat, Jan 15, 2011 at 10:38 AM, Teslalabor <teslalabor@xxxxxxxxxxx> wrote:

> Hi John,
>
> in my doubler, I'm using a 2kV MOT which is doubled to 4kV. The doubler is
> regulated by a variac so I can adjust voltage from 0-4000V.
> So what I meant was, that I fed the VTTC with 2kV from this doubler circuit
> where it makes good sparks, and than, I removed the doubler and only put a
> 2kV MOT in place, where the sparks were not good, at the same voltage. This
> I don't understand. But I read in the web that also other folks recognized,
> that the VTTC only runs on a doubler and with a normal plate transformer
> not. So I'm surprised you got the same results in both cases. This tells me
> that the transformer-type maybe is an important factor when running a VTTC
> on AC.
> Have to check it tomorrow with a big plate transformer instead of the MOT.
>
>
> Regards
> Stefan
>
> ----- Original Message ----- From: "Futuret" <futuret@xxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Saturday, January 15, 2011 5:08 PM
>
> Subject: Re: [TCML] Is this 2,3kW Triode suitable for a VTTC?
>
>
> Hi Stefan,
>
> In the past, I compared my VTTC operation using 4.2kV, from a
> doubler, and from a plate transformer.  Both methods gave the
> same spark length.  The difference was that in staccato mode,
> I got better sword sparks using the doubler.  I don't know why
> you're seeing such a big difference.  If anything, the shunts in
> an MOT tend to reduce or limit the spark length.  I often remove
> the shunts to get more power, however that does make the MOT
> less efficient (more core saturation).
>
> Have you tried doubling the 2kV MOT output to get 4KV?  I usually
> use at least 4kV for my VTTCs.  The spark length generally
> increases linearly with the input voltage.  Of course the input
> power rises by 4x when the voltage is doubled.  Using a doubler
> should almost double the spark length.
>
> I usually use around 5kV maximum for the 833A.  Some folks
> are using around 7kV or more, but I'm not sure how they get
> away with that.  I tend to get internal tube arcs when I go that
> high on the voltage.  A lot depends on the coil design and how
> it loads the tube and how it's biased, the amount of grid feedback, etc.
>
> It's not clear to me how you obtain 2kV when using the doubler?
> Are you using a different MOT with only a 1kV output, which then
> gets doubled to 2kV?
>
> If the new triode has a graphite plate (rather than sheet metal plate),
> then it should be even better.  Graphite plates can be pushed to
> much higher power levels than sheet metal plates.  The spec sheets
> say don't let graphite plates get red because they may out-gas,
> but I let them get red anyway.  I haven't had problems with
> out-gassing....yet.
>
> Cheers,
> John
>
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: Teslalabor <teslalabor@xxxxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Sat, Jan 15, 2011 9:38 am
> Subject: Re: [TCML] Is this 2,3kW Triode suitable for a VTTC?
>
>
> Hi John,
>
>
>
> thanks! Think I will buy a TB5 Tube. Then I will use my 5,4kV plate
>
> transformer + voltage doubler maybe.
>
> By the way, my VTTC only runs with the voltage doubler properly (1 MOT +
> 3uF
>
> cap + diode).
>
> I tried to feed the VTTC with AC only from a MOT but the output is very
>
> poor. This means, the sparks are much longer when fed with 2kV from the
>
> doubler instead of 2kV from a MOT. What am I missing? Is it due to the
>
> shunts in the MOT and the caps in the doubler deliver some sort of pulsed
>
> power to the coil?
>
>
>
> Regards
>
> Stefan
>
>
>
>
>
>
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