Akula0083 30 Watt Self Running Generator.

[magpwr]

You made a mistake.   Pins 2 & 3 are not connected directly to the cap.  They are connected directly only to the pot.

hi verpies,

I have amended the drawing.

4069 pin 2&3 is connected together.

Looks like this slow oscillator is running and acting as trigger on it's own without any feedback from main oscillator.

There is some possibility the frequency may drift over time maybe due to component aging or temperature variation.

The creator of the circuit might have been lucky to get it right.


   

[verpies]

Looks like this slow oscillator is running and acting as trigger on it's own without any feedback from main oscillator.
There is some possibility the frequency may drift over time maybe due to component aging or temperature variation.

Yes and three unused CMOS inputs are free floating.  They should be grounded (as shown below) or those three inverters will oscillate spuriously ...but maybe that's the key to OU

[conico]

I can't believe, only one coil on that transformer?!

https://www.youtube.com/watch?v=juwm_W5-qAM
https://www.youtube.com/watch?v=gWjs0-WCMzs

[Ed morbus]

https://www.youtube.com/watch?v=d5OqqyuKljE

[TinselKoala]

Yes and three unused CMOS inputs are free floating.  They should be grounded (as shown below) or those three inverters will oscillate spuriously ...but maybe that's the key to OU

Maybe it is.   
Actually an "unused" CMOS input can be configured to pick up the electric field from, eg, a HV secondary coil, and then the output of the gate can be used in a feedback circuit to make the whole affair seek its natural resonant frequency. I don't know if that's what is happening here, but it's a technique used by SSTC builders.
For example: