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Old 05-17-2019, 10:30 AM
OldTimer OldTimer is offline
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Join Date: Oct 2014
Location: The Netherlands
Posts: 10
Ha, this is getting more and more strange it seems.

Ok. First: with charging batteries disconnected, the neon lights up immediately, and the voltage across base/emitter rises steadily, without jumping up. I cut it off above 1v.

With the coil wire to the cap disconnected the neon does not light, and the voltage across base/emitter is zero. (both with charging batteries connected and without)

And I hear you, because something doesn't feel right about it from the start, but I can't put my finger on it. Just a gut feeling, but still. What it might be, however, is beyond my understanding at this point in time.

Because as far as I can tell from your questions and the results of the tests so far, the transistor is behaving as expected (more or less), and the circuit is also behaving as expected (more or less), apart from the jumping up in voltage and I guess current that doesn't seem to want to be restricted by a resistor. Although the resistors I use are quite a lot bigger in Ohms than the one from the original circuit.

Is it possible that the coil as described is actually too small? I'm thinking that this circuit should provide a frequency-driven charging action, where the frequency is determined by the size of the cap as far as I understand. Is it possible that the coil is off by for example a factor 10, and therefore gets into some kind of 'overdrive' mode where it becomes self-amplifying? Or am I talking rubbish here?

Just realized something else which may or may not be relevant: the resistance of the coil wire with the 100 turns bifilar (so 200 total) was listed as approx 2 Ohms per strand of wire in the original diagram, where mine are 1.5 Ohm. Don't know if that would make a difference that might add up to the jumping behavior?

Cheers,
Paul
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