Well my inexpensive upgrade of the cube just took a $200 Hit. I toasted my extruder... didn't realize the fan was not spinning.... Live and learn...
Trying to see if the extruder would get to temp on 12V without a fan is a BAD idea.
Eeeek! you killed a $2.50 thermal fuse. Just bypass it (short the cables leading to and from). You'll find it wrapped around the hotend. If the thermal fuse blows due to excessive heat, the hotend gets no power. I did exactly the same thing. Marlin firmware does have a failsafe against this anyway.
total printing noob here dan.. but where is the thermal fuse? I think I blew mine