| The older Roco drive in the Atlas Alco switchers had a headlight only. By removing the board, an M1 decoder can fit in the notch over the motor and not have to go in the cab. You can also add Golden White LED’s for the headlight and backup light in the cab. |
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Fig 1: If possible, carefully remove the handrails from the model. This may take a while, but you’re less likely to break them while installing the decoder. At least remove the ones from the steps to the back of the cab. Remove the body by carefully prying off the cab from the bottom then tilt the body forward to disengage the front latch. |
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Fig 2: Remove the PC board by removing the screw and unsoldering the wires. |
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Fig 3: Remove the weight and put Kapton or electrical tape on the four places shown that may contact the chassis. |
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Fig 4: Turn the chassis over and put tape on the bottom of the motor to insulate it from the chassis. Replace the motor screw with a Kadee Delrin screw or other non-conductive 2-56 screw. The hole in the motor is metric, but the 2-56 screw can be forced in fairly easily. |
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Fig 5: Replace the weight and solder the gray decoder wire to the motor brush. Do this quickly to not melt the plastic brush retainer. Solder the red wires to the right side pick-ups and the black to the left. The decoder wires are long enough that if you strip some insulation from near the middle, you can solder it to the front wire and fold it back and solder to the rear wire. Make sure you put the shrink tubing on the correct ends of the wires before you solder them. Cut the orange wire to reach the mounting screw, tin it and bend a loop to go under the screw head. Reattach the weight with the wire under the screw. |
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Fig 6: The decoder will fit in the notch with the flatter side of the decoder facing up. The large component fits next to the motor brush (facing down). Hold the decoder and wires in place with tape. |
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Fig 7: Cut a Golden White LED to fit using the original PC board to see how far the LED should stick out to almost touch the light pipe to the headlight. Solder the blue wire to the positive lead (the smaller part of the LED lead frame that you can see is the positive lead, so you can tell after you’ve cut the leads to fit) and run an extra blue wire to the rear of the engine with the yellow wire.. Solder a 1K ohm resistor to the other lead and then to the white wire. Shrink tube all the leads. I use DAP BlueStik (also called Fun Tak or Duco StikTak, etc.). You can get it in a craft store in several colors. It sticks to almost anything, but it’s removable and reusable. It’s great for sticking down decoders and wires. |
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Fig 8: For the rear light, I attached black wires to the LED and shrink tubed the connections and the LED to cut down on stray light into the cab. I used DAP Bluestick to hold it in the roof against the lens. Then I ran the black wires down between the windows to hide them and taped them at the bottom (the cab is shown backwards because it tips up and back on the chassis). Put the hood back on, tuck any extra wires under the hood and snap the cab back on. |
