craftsman garage door opener 139.185906 stop working
The old garage door opener stopped working yesterday. I opened the cover of the door opener, it looks the gear connected to the motor shaft is turning, but the other big gear connected to the chain does not turn and there is a lot of white things around. I guess the big gear is worn out and need to be changed.
The door opener is craftsman 139.185906, but I can not find the manual anywhere and do not know the part number. Please help me out. Thank you in advance!