Most older models can also be modified to accept DCC decoders, even those that have 'split chassis' arrangements,
although a little modification is required.
The wiring rules are the same as those detailed in Removal of DCC Sockets
and Hard-Wiring DCC Decoders.
Decoder wire colours are simple:
- RED - track pickup - by convention, the right side of the loco (although it doesn't actually matter)
- BLACK - track pickup - by convention, the left side of the loco (although it doesn't actually matter)
- ORANGE - left-side of motor terminal
- GREY - right-side of motor terminal (switch orange/grey around if loco runs backwards)
The key to converting a split-chassis model to DCC is to isolate the chassis from the motor terminals. Split-chassis models rely on
the motor terminals pressing against the chassis directly, to get power from the track, but DCC needs to intercept this connection and
place the decoder between the pickups and the motor.
This can often be achieved simply by soldering the decoder wires to the appropriate place, and using electrical tape, or heat shrink to
get the isolation, but this requires some flexibility in the space available. Often it is better to grind some space around the motor
terminals. Note that you will most likely need to disassemble the chassis to get to the motor terminal and for grinding.
Essentially that is all there is to it - the key being that the decoder must sit BETWEEN the pickups (chassis) and the motor terminals.