Royboy:
Thanks for a prompt and positive response. I temporarily wired one lead from an LED lamp to ground on the 520, and wired the other lead to BRUSH 1 (brighter) and then to BRUSH 2 (dimmer). As you said, when I reversed the e-unit the light output changed accordingly.
I'll shop at DIGIKEY for the parts you mentioned. With appreciation,
Mike Mottler LCCA 12394
mottlerm@gmail.com