I’m looking for any information on which dedoder and how to install into my older AHM Rivarossi 2-8-4 Berkshire. How do I isolate the motor and run wires to the tender for electrical pickup? Thanks.
Does the tender have electrical pickup ? If there’s no wire between the tender and locomotive, it does not, so you don’t need to add wires between them. I have installed TCS T-1 or M-1 decoders into older Rivarossi models and there was no power pickup from the tender. The decoder can be fit onto the top or right in front of the motor, and the motors were already isolated from the frame so that was no problem.
The engine pick up track power from the tender pin and drawbar on the engine. The round motor is bolted to the casting frame and one wire from the back of the motor goes to the drawbar. The other contact is sodered to the motor frame and bolted directly to the frame casting.
Does this engine run well enough to justify the cost and trouble of converting it to DCC? My experience with Rivarossi models that used the drawbar as a contact point between the tender and loco was that this method was very unreliable.
If you want to proceed, the first thing you have to do is remove the motor and put insulation between it and the frame, and find a nylon machine bolt instead of metal to secure the motor.
Then get some of the Miniatronics Micro Mini Connectors with 3 contacts. One contact will be used to get power from the frame back to the decoder in the tender. This will probably be the left rail, or black wire. Two wires will be used to get power from the decoder to the motor. If you also want to power a headlight from the decoder, you’ll need a second set of Miniatronics Micro Mini Connectors with two contacts to go from the decoder to the headlight. The decoder will get its other rail pickup (red wire) through the tender’s pickup wipers.
Isolating the motor from the frame is going to be the most difficult part of an installation of this type. Note that you’re also eliminating the flakey power pickup through the drawbar.
Back to my original comment – does the engine run well enough to justify the cost of a decoder and the Miniatronics Micro Mini Connectors? They’re not cheap.