It really easy. Wires are held in place with small slip-on plastic clips. Remove these clips and pull the wires out of the holes. If your models are like the GP-35, the Athearn board is riveted to the top motor contact strip. Very carefully remove the board because there is a brush spring under the clip that can fly away if you're not careful. Drill out the rivets that hold the clip to the stock board so you can salvage the clip, solder one of the decoder wires to it, and replace. The motor has to be removed to get to the bottom contact strip and solder a decoder wire to it. Be sure to insulate the bottom motor contact strip from the frame.
A lot of the boards on Athearn's use two little clips some times white sometimes black locate either side of the center of the decoder,( you can see one of the clips just forward of the NMRA plug the other is semi hidden uner the wiring harness with the wires disconnected as mentioned by another poster push one of the clips inward while lifting the decoder up as soon as the board clears the clip just remove it.
I suggest you discard those plastic lock clips Athearn still insists on using and solder your wires directly to the board.
CB&Q4-8-4FanaticDavid I am using the 9 pin plug. It currently has a NCE D13SRJ decoder in it. But i want to remove the light board to replace it with a Tsu-1000 decoder.
Why not remove the NCE and plug the TSU-1000 into the 9 pin plug ? The TSU-1000 has the light, sound and motor controller built-in. You won't need the NCE decoder. I just did the same upgrade with an Athearn SD50 and a QSI revolution-U decoder. Plug and play.
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
You keep calling it a light board. Are there LED's wired directly on the board?
Springfield PA
HamltnBlue
Yes the led's are wired directly to the board with the athearn plastic clips.