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The line of black items 3rd row down are the flyback or catch diodes... therefore the issue probably wasnt back-EMF spiking but decelleration surge... that makes more sense if other parts died that...

I may be teaching Granny how to suck eggs here, but that's never stopped me before :smile:

Catastrophic transistor failure in CNC is usually down to an inductive load.

eg: An NPN transistor...