Many thanks to Dick Sutcliffe, Superintendent BR &T Railway Co. for this application note!
Install the DN121 in the tender
1. The tender is easy to open by removing two screws so you can pull the decoder out and put in a plug when running on DC layouts.
2. Use a piece of styrene to raise the decoder off the weight.
3. Notch the front edge of the tender frame to bring the wires through to loco (all power pick up is in the loco).
4. Split the loco frame to isolate the motor brushes, remove the contact springs in the frame & heat shrink the wires to the brushes.
5. I drilled & tapped a couple of 2/56 screws into the frame halves for the track pickup connection.
6. Runs quite well but I am planning to put wipers on the tender wheels to spread out the pickup and improve operation