NMJ sells a drop-in DCC printed circuit board replacement for the NMJ Skd 224. The set comes with the new board and new wheels. The new board has a built-in Train-O-Matic Lokommander I decoder and a large capacitor for keep-alive.

First step is to remove the sheel of the locomotive. This shows the orignal PCB with has a NEM652 8-pin connector for a DCC decoder.

To remove the orignal board the wires that connect to the wheels and the motor needs to be disconnected. The board itself is fixed to the frame by two small screws.

A board comparison. To the left the orignal board, the board to the right is the new board with built-in decoder. Also visible is the large green capacitor.

The new board is installed on the frame.

The wires are soldered again.

The shell is placed back on the model. What is left is the old board and the decoder that was previously installed.

Flipping over the model and removing the cover plate and you get access to the wheels. The original wheels have plastic gears. These gears sometimes get loose on the axle and that creates problems.

The old wheels to the left and the new wheels to the right. The key difference are the brass gears that are mounted on the new wheel sets.

New wheels installed and ready to get the cover back installed.

First test, to make sure it all works fine. See video below for more details.

A quick demo. The built-in capacitor allows the small switcher to run over a piece of paper towel.