Take a close look at the field contacts for pitting
before scrapping your old regulator.
Use a strong hand lens to inspect the contacts. You might use some emery cloth to clean the points &
then use crocus cloth to final polish them.
Usually is what causes trouble in the reg. Use a clean cloth--such as a handkerchief--to pull
through the contacts for final cleaning.
Might need it sometime for a back-up unit.