The Decoder Buddy is a great circuit board for using the 21 pin decoder and allowing far more lighting functions than factory boards. I actually know and am friends with Nick, the inventor and producer of the Decoder Buddy product.
I have several models with the original first run Decoder Buddy's installed in them and they work great, with the added advantage of being able to separate the lighting plug from the board when separating the shell from the chassis.
The electric pick up wires, motor wires, speaker wires and keep alive are all soldered to the solder tabs on the Decoder Buddy board itself and all lighting and other function wires are soldered to the lighting plug on top of the board.