Yes, my first intention was to use the same topology as the original but I need to make this from scratch with new components because the original parts are no more in production so I need some new ones with the same characteristics in order to be able to replace them easily....
If you see the first (fritzing) schematic I posted before you can see the right components..
The original transistor is a 2SD2422 (no more in production) replaceable with a 2SD1415 (same as the other). The new TTD1415B is difficult to find for me....
The original zener diode is rated at 91V as in the schematic..
Do you think that I can use a TIP142 (easily to find) and a 91V zener and utilize the schematic of my first post?
In this case my previous questions about the "safe" behavior for Arduino pins remain open mainly because in this configuration when the zener "open" the current will flow back to the base of the transistor...
MarkT thank you for your replies and patience.