Re: [TCML] 3-500Z tube coil project

[Jason Johnson <jasonmsusolar@xxxxxxxxx>]

On Wed, Jul 14, 2010 at 9:16 AM, <futuret@xxxxxxx> wrote:

> Jason,
>
> Your design seems OK I think.  I tried a 3-500Z a few times in a VTTC,
> but it was back when I was just learning about VTTC's.  I got 17" sparks,
> but longer sparks should be obtainable.
>

That is good news, since I was hoping to obtain about 18" sparks. Do you
have any other advice or coil parameters to share from your 3-500Z VTTC
experience?


>
> If you need tighter coupling, you can usually raise the primary slightly,
> so that the bottom of pri is higher than the bottom of the secondary.
>

Right. As of now I am planning on winding my primary on a piece of heavy
wall PVC, and allowing it to be adjustable in height by sliding up or down
the PVC. I am guessing that this is a fairly critical adjustment to make, I
am just not sure of the best range on tube coils. Right now, I was planning
on making the primary form about 1/2 the secondary height, so 9 or 10
inches. If I don't have to worry about putting the primary too high, I may
cut this down.


>
> I think there are two types of 3-500Z, one has a graphite plate, the other
> a sheet metal plate.  I would assume the graphite plate can handle more
> power, although the spec sheets might not suggest that.
>

Yeah. I've got the lower power metal plate version. Though if/when I blow it
up I may replace it with a 3-500ZG from rfparts. I am planning on building a
staccato circuit at some point to hopefully push the peak power envelope w/o
over doing the average power numbers.

Speaking of pushing things, there is a note in the 3-500Z spec sheet (
http://www.umich.edu/~umarc/station/docs/3-500z.pdf) that interests me. On
page 3, the last set of ratings given are for a switching modulator, which
lists the DC plate voltage at 10 kV yet maintaining the DC plate current of
400 mA that is common to several of the other modes of operation. What is
the difference between this type of operation and the standard Hartley type
oscillator used for VTTCs? Can I make use of some of this voltage headroom?


>
> My website is:     http://futuret.110mb.com
>
> There's a menu there leading to my VTTC pages.
>
> John
>
>
Yes, I have been admiring your work for quite some time now, including the
nuggets of advice dug up from the TCML archives...There are also many other
webpages that give you due credit for your work and your willingness to
share the knowledge :-)

Thanks,
- Jason
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