One thing you can do is to make sure that your amp light is still good.
The current through the amp light furnishes the excitation for the
alternator, so if the amp light doesn't work, the alternator may not also.
If I remember right the excitation comes to the alternator in a small red
wire. In any case it is a small wire - a very small current. You can
disconnect it and check with the ignition turned on - should get 12 volts
to ground there.

You can look at the regulator and see the wirewound resistor on the bottom -
if it is burnt the regulator won't work. Also if you can open it easily
(with it disconnected) make sure the points inside, 2 sets, are clean and
working OK and not welded together. (Manual says not to mess with them.)
You can clean them but you will probably have to adjust them if you do -
when charging you want 13.5-14 volts. Not all of my efforts in doing this
have been successful....
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George Downs Bartlesville, Oklahoma