Hot electronic voltage regulator when key left on

Have a friend that was doing some trouble shooting and left the key in the run position and noticed the electronic voltage regulator was hot to the touch. 1970 type voltage regulator.
My thoughts were that the regulator is getting hot trying to energize the alternator and without it spinning overheats the regulator.
Thanks.

Bad stuff happens to ignition systems, too, when you leave the key in the "run" position while the engine is not running. So don't do it. If you need to trace some circuit, use a VOM or powered circuit tester.

It'd be getting hot from "full fielding" the field circuit to raise the system voltage to what the reg is built for which ain't working since the alt ain't charging/raising up the system voltage even with the reg constantly grounding the green field wire to max it out. reg is flowing max current

Thanks, that was my take on things.