sentences:  The issues with the earliest version of the SVT were in the early design of the driver circuit, not the 6146B tube which is a stable and reliable tube.The earliest SVT driver circuit's design would on occasion result in blown 6146B tubes.Because the front end 12BH7 voltage amplifier is fed from the 430 V node, during loud transients and overloads this will produce an AC signal that far exceeds the 12BH7 follower that has 220 V on the plates.