The So-Called Don Smith Generator

[Magluvin]

Hi Tesluh,

Well, your driver and the flyback trafo are nice but you are limited in the flexible changing of the HV output frequency versus the other oscillator circuit and the HV trafo shown in the PDF file I referred to yesterday.

I do not know the inside circuit of the NST what Don Smith used, my best speculation is his NST had a center tapped secondary coil output i.e three output wires and the two diodes worked exactly like a center tapped full wave rectifier circuit works, you are surely familiar with, see this http://www.electronics-tutorials.ws/diode/diode18.gif  and the three wires are A, B and C, C center tap is the common negative (ground symbol). The schema is from this site: http://www.electronics-tutorials.ws/diode/diode_6.html

Now, in your flyback trafo you have only 2 output 'wires', see my attachment 1.

In the second attachment I encircled the positive (red) and the negative (blue) connection points in two Don Smith circuits (they are familiar, aren't they) where I think your flyback trafo outputs should be connected, with the correct polarities. You need to identify the negative HV pin of the flyback trafo, of course but I believe you already did.      

The flyback trafo gives a half wave rectified HV output while the NST output (if the center tapped assumption is correct) gives a full wave output; this means the spark gap can fire once from the flyback output during a full T period (T=1/f) and can fire twice from the original NST output during a full period. This means you need to tune L1 (the primary coil) to the spark gap frequency accordingly.

Gyula

Im reposting the 2 circuits.

In the top circuit which seems to depict the circuit just after the nst, its an odd config. The cap is across the first pri coil. Being so, I wonder if the cap is actually being charged by the nst. If the primary and the dual secondary are say lenzless, then maybe the spark gap to the nst gnd is just something that gets the pri lc going into resonance???    Strange setup.

Mags

[Tesluh]

l1 capacitor should adjust resonant frequency of primary tank down from MHz to kHz range to match the output of the power supply.  capacitor on l2 should make l2 resonant frequency match l1, at least that is how I understand it:)  not an easy task but I don't think it will be impossible.

[gyulasun]

Hi Mags,

I simply answered member Tesluh's question where he could connect the HV output of his flyback transformer when he omits the nst in DS schematic. And there are some variants of such schematics on the web so I took the ones found in the uploaded paper in the very first post of this thread, after all this thread was started as 'the so called Don Smith generator'. (Using the internet wayback machine the deleted file is there.)
By the way, I also find the first circuit a strange configuration. The same schematic is included in PJK's book, Chapter 3 but I do not mean this justifies the circuit either...   

Gyula

Im reposting the 2 circuits.

In the top circuit which seems to depict the circuit just after the nst, its an odd config. The cap is across the first pri coil. Being so, I wonder if the cap is actually being charged by the nst. If the primary and the dual secondary are say lenzless, then maybe the spark gap to the nst gnd is just something that gets the pri lc going into resonance???    Strange setup.

Mags

[Tesluh]

I have probably looked at over a hundred schematics for just this device alone!

[Magluvin]

Hi Mags,

I simply answered member Tesluh's question where he could connect the HV output of his flyback transformer when he omits the nst in DS schematic. And there are some variants of such schematics on the web so I took the ones found in the uploaded paper in the very first post of this thread, after all this thread was started as 'the so called Don Smith generator'. (Using the internet wayback machine the deleted file is there.)
By the way, I also find the first circuit a strange configuration. The same schematic is included in PJK's book, Chapter 3 but I do not mean this justifies the circuit either...   

Gyula

Hey Gyula

Yes it is strange. But the top diagram is the same as the photos. It would be interesting to just see what happens with that part of the circuit alone done as shown.

Mags