I've made this circuit on a breadboard. It doesn't work properly.
I hear the sound of an oscillator (similar to the sound of 555 timer).
I changed C6 and L1 to change the frequency but I hear the same sound.
When I use 3K ohm instead of R2, the frequency increases (the tune of the sound is higher).
The transistor in the circuit is not available for me. so I used other transistors (general purpose, switching transistors and amplifier transistors).
I'm using 5 volt instead of 3 volt.
I want to know what is the problem? and should I use a zener diode or an ordinary diode?