Dryer was working until I turned the start knob. There was a pop sound and we thought all we had to do was replace the knob. After replacing it we tried to start it and nothing happens. If you put your hand on it while turning the start knob you feel a faint vibration

First check to make sure you have 220 volts going to it and that you did not pop a breaker. Next check the thermal fuse for continuity. Unplug unit and remove 1 lead frim it. If no continuity, replace it. It is about 3/8" wide and about 3" long and located on the back side of the blower motor housing