Amp light full red on startup?

[Bigbunt]

This is one of those little mysteries that I'm only asking about because it's intermittent and has the potential to leave me stranded...
Every once in a while when I start my B20 in the morning, the amp light comes on full bright red. Normally it does the flickery reddish behavior which I've gathered is completely normal, but this is unblinking. It hasn't ever stayed on past the end of the driveway but my concern of course is that I'll go out at night and it'll come on and stay on and leave me without a charging system.
I'm kind of assuming my regulator is a little sticky but not sure if that is it and if it is, can it be freshened up or should it be replaced or whatever.
This car still has a generator which seems to be fully functional, with lots of life left in the brushes...but it is (probably) 48 years old.
This novice defers to the learned ones among us... Thanks for any thoughts.