With the Uhlenbrock 73400 decoder, converting the SD70/75 is fairly easy. You still have to pop the floor out of the cab, but the Uhlenbrock fits easy. It only has 6 wires, and the AZL light board has 6 solder points, with a number. Number/Wire Color 1/Orange 2/Gray 3/Red 4/Black 5/White 6/Yellow Cut the wires length so the decoder end sits flush with the front end of the chassis. This means the red and white wires are a tiny bit longer than the orange and gray, and those are a bit longer than the black and yellow, so they all fit perfectly. Pull the copper light board contact strips off for DCC use and solder tin the light board solder pads first, and the wire ends next, then very quickly solder the decoder wire ends to the top surface of the light board. Now cut a small piece of black electrical tape and fit it inside the cab to cover the windows, then put the shell on, and the decoder will be sitting in the cab area. Carefully slide the cab on and turn on the forward lights after programming your decoder. If the light leaks out, just fit more black tape and try again. -Robert
