It worked, thanks for the input. For future reference, the astable oscillator diagram has an error, shows C1 as a ceramic capacitor of 0.047uf and then overlaps it 10, I did not notice it until now, then in the assembly it shows it as a 10uf electrolytic capacitor. Well, yes, it is really a 10uf electrolytic capacitor; In my case, in this specific model I had to modify it to one of 47uf / 16v, that gave me more range to modify the frequency with the variable resistance. Works!!!