Spectrum wiring

[Andynewbe]

Hi,
 I'm new, and looking for a solution to the following.
I have a Spectrum 2-6-0, and am trying to figure out the wiring, as I'm putting in a new decoder.  It seems all wired wheel pickups go to a central mini circuit board at the rear wheels.  The top of the mini board has 4-wires coming out and going to the upper board, which are again connected to the Bachmann decoder.  Those four wires are Brown, Orange, Red and Yellow.  On the opposite of this mini board there are two yellow connectors.  I don't have a clue as to what these are.  Any ideas?
I should also mention that there are two wires coming from the lower circuit board rail pickups to the upper circuit board which again go to the Backmann decoder.  
Also from the upper circuit board  those four wires go to the fire box.  Does this fire box require these four wires?  Or are the four wires used for the box flicker?  My new decoder doesn't have a four wire flicker connection.  What do I do here?  Any help would be appreciated.
Thanks
Andynewbe