My garage door opener (Craftsman 1/2 HP) stopped working some time ago (even lights didn't come on). I replaced the circuit board and now the lights are working and the board reacts to the remote (rapid blinking) but the motor doesn't start (doesn't even make a noise). I decided to replace the motor but it didn't help. There is a large capacitor between the CB and the motor. When I press the remote my voltage meter doesn't show anything on that capacitor's legs. Could it be the capacitor?
When I was working on modifying my garage door opener, I found two things:
One of the failure sensors was tripped; there are several, but the one that got me was the obstruction sensor. It was incredibly easy to bypass by short-circuiting the sensor's connection with a jumper wire.
The communication may be off, especially since you replaced the board and remotes sometimes don't clear their memory so well; check the blink patterns in the diagnosis manual. The blinks may indicate that the remote's rolling keycode pattern is incorrect. This is exactly what happened to me.