This installation is for HO-Scale Athearn SW 1500 uses TCS M1 Digital Decoder and was performed by Jim of East Granby, CT
I fastened the decoder inside the shell just forward of the motor - there's no room directly above the motor in this locomotive.
I lifted the motor straight up off the frame and popped off the lower and upper brush clips. The lower clip has a set of prongs which are bent down to contact the frame. I cut these prongs off and flattened what was left back into the clip. I exchanged the clips so the one that used to have the clips is actually on top of the motor. I soldered the gray motor wire to the clip on the bottom of the motor and the orange wire to the clip on the top of the motor. I covered the bottom clip with electrical tape and re-installed the motor onto the frame.
I soldered the black supply wire to the front lamp bracket which, in this case, was securely riveted to the frame. I soldered the red supply wire to the front truck contact and jumpered another length of wire to the rear truck contact. The original headlamp and metal strip picking up power were removed and discarded.
I installed front and rear 14v 30ma incandescent bulbs using some double-sided foam tape, and wired the bulbs to the decoder as shown in the photo. I fastened all the light wires to the inside of the shell using a variety of foam tape and double-sided poster tape (thinner than the foam), and covered the exposed soldered connections with some plastic storage-type tape.
The motor and supply wires were sized so that with the shell on the frame the wires should be clear of the flywheels. This worked out fine for the motor wires - the extra length of wire forms a loop along side the motor and can't get in trouble. If I had to do it again, I would have brought the supply and frame wiring along the frame to the front end of the motor and done the same routing up to the decoder as the motor wires. As it is, I carefully assembled the shell and frame, tucking the supply wires up into the corner of the shell, and I think they will be ok there.