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Forums
4hv.org :: Forums :: Tesla Coils
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Little VTTC with 807

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Patric
Thu May 31 2012, 07:45PM Print
Patric Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255
Little, cheap, possible to tune it! Little spark, but it can work for hours!


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Patric
Sun Jun 03 2012, 05:58PM
Patric Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255
This is the next step, some advise for improvement?
1338746283 2899 FT139241 Tesla807duo
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Mads Barnkob
Sun Jun 03 2012, 06:36PM
Mads Barnkob Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Patric wrote ...

This is the next step, some advise for improvement?
1338746283 2899 FT139241 Tesla807duo


Make a tap on the feedback coil at 13, 14 and 15 turns, that way you can easily match the two tubes in parallel by varying the feedback to each one of them.
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Patric
Mon Jun 04 2012, 01:42PM
Patric Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Thanks, will try! And what about the screen grid resistors? There are many different ideas about them...
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Dr. Dark Current
Mon Jun 04 2012, 02:21PM
Dr. Dark Current Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I suggest at least doubling the tank cap value and decreasing primary inductance accordingly.

As for the screen resistors, the proper way is to rf bypass the screens with a ~10nf ceramic cap to cathode, however this also increases the transconductance of the tubes and may disturb the oscillation of a previously tuned coil.
And use individual resistors for the tubes of course.
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