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Dear Group,
I came up with a new way to build the tickler coil for a VTTC that has
overcome the magnetic coupling problems I was having with traditional
tickler coils. The tickler coil is wound at the base of the secondary
and connected directly to the grids, a potentiometer can be used to
reduce power.
Benefits found so far are:
1.) No need to move tickler up and down the secondary
2.) Tickler will always resonate with the secondary within a wider range
(sometimes the tickler and primary couple)
3.) Only turns number on the primary and tickler need to be adjusted for
tuning (rather than grid leak capacitance and resistance)
4.) There is no need for high power resistors for the grid
5.) Coil will resonate through a larger range of primary coil turns and
tank capacitance (mine works from 500khz to 2mhz)
6.) Tickler coil is hidden from view giving a cleaner appearance and
simpler wiring
7.) Very simple to tune
8.) Higher frequencies are easier to achieve
Down sides:
1.) Arcing secondary to ground drops the power down significantly
2.) Arcs are louder
3.) Possible over voltage of tube grids
4.) Thickness of wire affects power output (1mm wire gave me 2500W
consumption, 0.5mm (same as secondary) gives me 650W)
5.) Tank circuit experiences more over voltage and transients
6.) Frequency is a bit more unstable
I have made a video and schematic:
http://russianpoweredvttc.blogspot.com.au/2014/08/above-is-schematic-for-easily-tuned.html
I hope this may help someone experiencing issues with tuning. I was at
my wits end and this circuit has helped a lot.
Cheers!
-Wil
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