Installing a DCC decoder in a Bachmann Class 20 locomotive

Click on each image for a more detailed view.


Last updated 29 March, 2020
Bachmann 20

Before installing chip into any loco it is advisable to check the current being drawn by the loco. You should test the current drawn when the loco is stalled to find the peak current and select a decoder that will cope with that maximum current requirement.

Underside of Bachmann Class 20
On the Bachmann Class 20 the body is secured to the chassis with two screws, one at each end, hidden by the bogies.
Bachmann Class 20 dummy plug
Installing a decoder in this loco is really very straightforward. The most difficult task is making sure that you have selected a decoder that will fit into the small space that Bachmann have generously left the DCC modeller! You should not only select a small decoder but one that has an NMRA plug attached. Once the body has been removed the location of the socket for the new DCC chip can easily be identified at the front of the loco. Gently remove the small PCB in the NMRA socket by levering it out.
Bachmann Class 20 with dummy plug removed

Once the existing PCB has been removed it is obvious which way round the new NMRA board should plug into the socket as pin 1 is labelled clearly on the underlying PCB.

Remove the capacitor before inserting the NMRA plug - a pair of small wire cutters can be used to snip at each side of the capacitor. This action is recommended to improve the performance of the loco with a decoder installed, but be aware that disabling the capacitor may invalidate your warranty.

Bachmann Class 20 with decoder installed

Insert the NMRA plug into the socket with the orange wire occupying the pin 1 position. In this case a TCS M1-P decoder was used (though it should now be possible to use a TCS DP2X-UK plug-in decoder). Secure the decoder to the internal casting with a self adhesive sticky pad (Sellotape Stick Fixers from W H Smith or any good stationers are ideal) and neatly position the wires so that they do not cause an obstruction when replacing the body.

The decoder can now be programmed, preferably on a programming track, though TCS decoders can be programmed on the main line.

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