The guy I bought the controller from says all his LEDs are common voltage - haven't heard back from the other person yet.

I think the easiest thing to do at this point is to rework the board back to original function before it gets too complicated to do so, and pick up second set of LEDs. I can hopefully pass the current set along to a friend who doesn't need to use the alternate controller.

Everyone, especially Mark, thank you so much for the assistance. Even though the rework didn't work, it was fun to do and good practice. Even though I really need a new soldering iron, or at least a new tip on this crappy one, I think I did a half-decent job. The anticipation of success by performing the mods was also a treat on what would have otherwise been a relatively dull day - weather was crap which pre-empted a few projects.