I looked at the NMRA guide for doing this, but I just want to make sure I'm using the right frame of reference. I've attached a pic of an 8 pin plug where you can see it refers to this being the top view. But is it "top" in the sense of where the wires go in for soldering, or "top" in that you're looking at the front / pin end that gets plugged into the socket?
NMRA 8 pin plug Pin 1 is pin 1. If you plug in the wrong way, the direction and lights will be reversed. The NMRA designed it that way to make it fool proof. No damge to the decoder. Top has nothing to do with this. The connector could be positioned upside down. Rich
Take a look at this page. It will show the NMRA 8 pin with the colors. You will have scroll down a bit to see the 8 pin plug-socket. http://litchfieldstation.com/DCC-University/SelectHarness.htm Should clear up some of the questions about this.
Note that in the Intermountain N Scale Cab Forward, the jumper plug is wired correctly, but labled wrong (it shows pins 5 thru 8 in reverse order). Use the above diagram as the basis for correct decoder connections.
