westexasmoker,
Yes, you can plug the cabinet directly into an outlet and bypass the smoke generator. However, it is not fused if you do this.
I'd start at the smoke generator and make sure it is providing 120 volts to the heating element. Just stick your probes in the outlet of the smoke generator that feeds the box and you should see 120 volts AC. Since this is 120 volts and not 12 volts, be careful.
If you have 120 volts there (or decide to plug directly into an outlet). You should be able to see some voltage across the heating element. I would back off the slider a bit from the extreme right, since some have reported a dead spot. If no juice, I would take the back off and look for the thermal breaker. Since I've never done this, not sure what it looks like. To eliminate the thermal breaker as a problem, you can short it. If everything works, then the thermal breaker is the problem.
At the temperatures you reached, I would also be looking at wire connections to be sure nothing fried or came apart.
Arcs_n_Sparks