It began with a basic slayer exciter.
Having the 120Ohm+470pF Snubber to protect the transistor together with a fast UF4007 in parallel.
The feedback goes through a 240Ohm + 100pF to protect the base and keep the current acceptable. The real circuit still suffers on that part as the Resistor (3W type) gets quite hot.
The Diode between Base and Emitter (often LED are used) is 1N4148.
All this (and I use in reality a 2SC5200 as BJT) is to keep the transistor alive and allow for up to 24V input voltage for longer than 30 seconds
