Have you checked voltage from the plug marked line to the pin marked N on the bottom of the board? I did read all your post but I donít know if you have checked this.
I am with richappy I think it is a loose connection of some kind.
If you could wait until Monday before you blow it up I will try to find a wiring diagram to it at the shop then I might be able to help more. But from what I gather you have probably already done everything I would know how to help you with.
Also plug that encoder back in because it is not your problem.