Many thanks Jim for the fast reply.
Just trying VE7VXO and after an hour I had over 1000 W adsorbed from power supplies and after few seconds one of both of final MOS went away.
By sure a coincidence but I think I will come back to 3.4b that worked many years with my IC-705.
As I use the IC-705 interface between linear and radio and I don't use any PTT cable, it could be not completely compatible with VE7VXO firmware.
Best 73s,
Maurizio I2NOY