Making a Test Board & Rolling Road for Analogue & DCC Model Locos

I’ve been doing an increasing number of DCC decoder installations and model locomotive repair jobs – both for myself and others – and setting up my tester and rolling road each and every time I needed them was becoming a bit tiresome (not to mention the rat’s nest of cables).

After pulling what’s left of my hair out for the final time, I decided to put together a small loco and decoder test board, incorporating my LokProgrammer and SPROG, as well as accommodating off-board control integration (DCC and DC/Analogue).

The board also features a rolling road, using DCC Concepts rolling road modules, and my own take on a means to permanently integrate them into a test set up and improve usability, using acrylic sheet, spacers and screws.

You can download a PDF version of the wiring diagram for the test board featured in the video via the link below:

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Wiring Diagram for DCC Decoder Test Board & Rolling Road 5.98 MB 463 downloads

This is a wiring diagram for the decoder/loco test boar and rolling road featured...

This is only one way of approaching a decoder test board setup and there other examples out there. I do recommend that you consider something like this if you’re intending to do a lot of decoder installation and maintenance – it saves a lot of time and hassle!

CORRECTION: in the video, I mention the acrylic/perspex sheet as being 6mm when it is actually 4mm. A thickness of 6mm is likely to be too thick and may interfere with the wheel flanges.

Project Components

You can buy some components for this how-to project via the links below. Buying via Amazon affiliate links means I get a (very) small donation and helps to support the website and channel:

– DCC Concepts rolling road: https://amzn.to/2C1IB6t
– Red and black wire pack: https://amzn.to/2C1Infx
– Green 2-pin terminal plugs/sockets: https://amzn.to/2PiVfiW
– Peco straight track: https://amzn.to/2LGgPM7
– A4 clear acrylic sheet (4mm thick): https://amzn.to/2Cae1Yk
– M5x8mm black nylon spacer: https://amzn.to/2Pq7tX4
– A4 plywood 12mm: https://ebay.us/LGRLYW
– A4 plywood 3mm: https://amzn.to/2C03bE2
– ESU decoder tester: https://ebay.us/aBLzSi
– SPROG dcc module: http://www.sprog-dcc.co.uk
– Green power panel-mount socket/plug: https://ebay.us/nBLfXz
– DC power-style socket: https://ebay.us/nBLfXz
– 3 position, 2-pole switch: https://ebay.us/WyKD3b

3D Printer STL Files

If you’ve got a 3D printer, you can download STL file for the 3D-designed parts for free and print yourself a copy:

Switch box/enclosure: https://skfb.ly/6B6Cy
SPROG3 cradle: https://skfb.ly/6B6DY

Please note: If you choose to follow any of the steps or suggestions outlined in the video, you do so at your own risk and any damage or injury to yourself, your models, your equipment or others is your own responsibility. Your own test board wiring requirements will vary depending on the components that you use and also the specifics of your design. The diagram provided above is only a guide and you must work out your own wiring needs yourself to avoid costly damage to programmers, testers and decoders.

How to use a 21-pin decoder in a locomotive with an 8-pin socket

Whilst we crunch through a mound of unedited video filmed during June 2018, we thought we’d put out a short tutorial outlining one approach for making a custom 21-pin to 8-pin harness to enable the use of a 21-pin decoder in an 8-pin locomotive chassis.

The adaptor is simple to make and works well, but by its very nature, an 8-pin plug will not enable all functions of a 21-pin decoder to be used. This is unlikely to be an issue in most cases, as 8-pin chassis locos tend to have few built-in functions.

If used with a sound decoder, separate wires will need to be soldered to the adaptor for the speaker connections; the schematic below shows the relevant solder pads. Alternatively, in some cases, speaker wires can be soldered directly to the chip.

Download a free PDF file of the wiring diagram here:


Items required for this simple project are:

– MTC 21-pin breakout board (e.g. Laisdcc or ESU)
– 8-pin plug (pre-wired, if possible)
– Reel of decoder wire (for non-wired plugs)
– Soldering iron, solder & liquid flux
– Kapton tape or insulation tape
– Various tools, including: small side cutters, wire stripper and an exacto knife.