Solid state tesla kit modifications

[Mephitus]

Been playing around with a tiny tesla coil kit that I received as a gift. Attached is a pic and the document that came with it (all in helpful chinese, lulz). At the full 24v I can get maybe 5mm of corona discharge. I'm interested in scaling it up a bit but am curious about a few design choices. Firstly with the cap at C2 that couples the audio output. Why is this cap tied to ground rather than in series with the input? Secondly, the LED in series with the secondary coil seems a bit strangely placed. Wouldn't this be better served with a proper diode? If there are any additional changes or strangeness with this I'm missing, I welcome any input.

[jcw0752]

Hi I have been playing with one of these too and I don't understand it that well but I think the C2 is a low pass filter that just allow the lower audio frequencies that the eye would register to affect the circuit. I could not see much change in my corona regardless of the audio that was put in. As far as increasing the height of the corona I suspect a larger number of winds on the secondary will be needed. With one wind on the primary we don't have much to work with on that side.
John

[james_s]

It strikes me as a very odd design. There are lots of example out there of SSTC builds, personally I think you'd be better off building a better one from scratch rather than trying to improve that one.

[strawberry]

... I think the C2 is a low pass filter that just allow the lower audio frequencies that the eye would register to affect the circuit. I could not see much change in my corona regardless of the audio that was put in. ...
John

C2 is just powersupply bypass capacitor . And MOSFET is adjustable voltage source. It will work more like peak detector, not as low pass filter
MOSFET dont have negative feedback in this circuit..

[Jwillis]

 This is what is called a Slayer circuit tesla coil .The LED is place reverse so it acts like a zener diode .When the circuit is on a current is at the base of Q2 switching it on.This starts current flowing though the primary coil T1and induces a current through the secondary coil pulling the bottom of the secondary to negative.This pulls the base of Q2 low and the transistor switches off .Voltage at the primary stops and a reverse voltage spikes in the secondary switching the transistor back on again.Rinse and repeat.The LED also acts a protection diode to prevent spiking on the base of Q2.So the coil will oscillate at a high frequency and the sound is modulated over that frequency .This makes the plasma of the spark change pitch according to the frequencies transmitted from the right channel.

If you need more Spark then a secondary with more winding's is required. Just make sure the primary and secondary remain in phase (the winding's go in the same direction).If more driver voltage is required then Q1 and Q2 will need to be changed to except the increased voltage and all capacitors will need to have a higher voltage tolerance. You can add a ball to the top of the secondary to increase the capacitance of the coil.That will increase the sparking as well.

If your interested I'm currently working on a variation of the Skori Mini SSTC and so far it's working very well.Check it out https://translate.google.ca/translate?hl=en&sl=hu&u=http://skory.gylcomp.hu/tesla/mini_tesla.html&prev=search
I linked through Google translate because the site is in Hungarian.