All wiring is stock/original. It was an untouched car when I bought it. The alternator bulb is incandescent, as it should be. The alternator charges perfectly when the engine runs, stable smooth DC at 14.4/14.6 V. Just occasionally turns itself on when it shouldn't. I'll look at the bulb in the dark next time I hear the whine.
What I can say is that it takes very little voltage to activate the regulator. I was able to turn it on with .3Vdc. Seems like it should take more than that.
I guess this is why most aircraft use an externally regulated alternator with a split master switch which allows the alternator to be controlled independently of the main bus.