How can I repair a Goot PX-201 soldering iron which was exposed to too high AC supply voltage?
Since there are no obvious burn marks, the electronic control circuit most likely got fried.  Whatever is doing the voltage regulation from the input AC to the low voltage the control circuit needs got severely abused.

Maybe you can read part number off the chips and find replacements, but if not this unit is toast.  Ditch it and move on.