Mr. Rodolfo.- I tell you: - If you build an oscillator of 15750 cycles, you can work the flyback without the oscillation of the jungle.- a 15 / 80vcd source to apply instead of the b + of the original source, and a probe of vpp. is in electronic community.- with these elements you can apply a low voltage to the b + of the flyback and you can monitor the vpp in the collector.- If at 50 or 80vcd, the tuning capacitors were bad, a warm-up is noticeable.- This allows you to have a tool to check the flyback.- Obviously this is not the solution just a contribution for your measurements. Cheers