In the late 60s, I bought a cheap voltage regulator from JC Whitney for a 1948 Chevrolet Panel Truck. After 200 miles (on a 400 mile trip), the lights got real bright for a short while. Then, we smelled an odd odor from the engine compartment, and the ammeter registered zero.

A quick inspection of the engine compartment directed me to the smoking generator that was ruined (solder, I think, was all over the opening in the generator from over-charging and over-heating). It was late at night on a country highway. I drove until the battery was so low that the lights were useless. The next morning, the engine started and I drove home on the battery power.

I now carry a spare voltage regulator and generator.