No joy on finding a schematic for a LiftMaster control board. Thought I'd
ask here.

The remotes (4 of them) work flawlessly to open the door. They also work to
close the door, but only after the built-in overhead light turns off. That
takes about 2 minutes.

Checked the obvious for the beam sensor: sensor obstruction, sensor wiring,
sensor lenses, sensor alignment. The wall switch always works.

Any ideas?

Thanks!