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Re: Tuning Question
Original poster: otmaskin5@xxxxxxx
Thx Terry, I appreciate the suggestions. FYI, when the NST died, it
just is weak on one side, have to get a ground right to the terminal
to get an arc & then the arc won't stretch nearly as long as it does
on the other (good) side. Shorted? BTW I do have a Terry filter &
safety gap between the NST & spark gap. Thanks again, Dennis
-----Original Message-----
From: tesla@xxxxxxxxxx
To: tesla@xxxxxxxxxx
Sent: Mon, 20 Nov 2006 9:06 PM
Subject: Re: Tuning Question
Original poster: Vardan
<<mailto:vardan01%40twfpowerelectronics.com>vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
Hi Dennis,
At 06:30 PM 11/20/2006, you wrote:
>I've read plenty about the importance of tuning coils at low
power >(variac & gap width) to avoid damaging components until
resonance is >achieved. I also recall a post discussing, once a coil
is tuned at >low power, you need to further tune the coil at full
power due to >additional secondary capacitance created by the
streamer itself. I >have some questions about this.
>Is additional capacitance of a full power streamer
significant >enough to warrant the additional tuning excersize?
"Barely" it depends on the coil, but it is about +5% added to the top
capacitance. Problem is, just "moving" the primary "wires" is just as
significant. In general, tuning the primary frequency 5% low is fine.
However, it might not make much "real" difference at all. Solid state
coils with there deadly reproducibility and guys with crystal control
frequency counters and such can "detect" the difference, but nobody
else can ;-))
>If so, I would assume you are looking to increase primary
inductance >to compensate for increased secondary capacitance - so
you'd be >tuning outward (increasing primary turns) - correct?
Yes, the primary should be tuned a little lower in frequency from the
secondary.
>I tried this & seemed to find increased performance tapping
the >primary at an additional 3/4 turn - i.e., from 13 7/8 turns to
14 >5/8 turns on my 15/60-0.015uF system. Seems like a lot
of >additional primary for the small increase in
secondary >capacitance. Does this seem to be in the ballpark for full
power tuning point?
Whatever give best performance is fine. The problem is when you moved
the tap point you also moved "the wires" going to those points. Those
wires are just as significant in varying the inductance. No hard
rules there, but to just "fish around" for the best sparks. Recently
I have tried to keep the wires going "down" at a "90 degree angle"
which removes them from significance. That works good.
>My NST died a few days after reaching this higher
performance >level. I'm wondering if I killed it with improper tuning.
I doubt it. The firing tuning should not kill an NST no matter what.
Your cap is the LTR value too with a fixed gap... Sometimes old NSTs
"just die"... But aside from old age, I can't see anything that
should have hurt it. what when wrong with it? Shorted side? Maybe
just the old tar arced through...
You gap should "short across" the NST too. See the conclusion at the
bottom of the page here:
RF stress on the windings will kill about 5% to 10% of NSTs given time...
>
>I want to optimize performance, but would also like to avoid
killing >another transformer.
>Any tips or suggestions on doing this additional full power
tuning >excersize. I'm concerned I'm missing something here.
There is always the "Terry filter".
<http://hot-streamer.com/TeslaCoils/Misc/NSTFilt.jpg>http://hot-streamer.com/TeslaCoils/Misc/NSTFilt.jpg
It seems to make killing NST super hard to do... But in general, you
seem to be doing things "right".
Cheers,
Terry
>Thank you - Dennis Hopkinton MA