Rob, it may be a bad part here..although I always use brand new parts, some defective part may have been soldered to the PCB.
Tried alot of things and am not getting oscillation with the MJE3055t..just gets hot instantly!
Switched the primary winding, feedback windings, tried lowering the resistor value, raising it, changed the capacitor..still gets hot and no output..
Switched the toroid to another board I made and it's ok..get 450 volts at 450 windings.. oscillates on that board so it's wiring, parts placement or a bad part.

John