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I have an Athearn EMD SW7. Looks like one of the motor contacts routes through the chassis. Any hints on fitting a decoder? Initial thoughts are just to insulate the lower motor contacts, which are metal strips, underneath the motor from the chassis. The upper ones (the white wires) would just need to be cut. The the decoder can be wired in from the chassis to the lower contacts, and in the gap(s) in the white wires. I'm not interested in sound so that isn't an issue as there is plenty of space to locate the decoder at the cab end.
I remove the bottom tang which contacts the frame, drill & tap a 2-56 hole, and attach the red or black wire to the frame that way. There are a couple of small decoders, N or Z scale that have enough amperage to run this motor, and take up less room, and will fit right on top of the motor if you want, and don't clog up the cab space with a bunch of wires. Not hard at all. Keep the two upper wires and connect them to the other rail lead wire (red/right - black/left). I solder everything, no press fits. The headlight goes away and is replaced by the proper bulbs & resistors as necessary.
