Dapol N Gauge Class 22 Diesel with Zimo Sound

Kit: MX660; SugarCurve6; LifeLink; 2x Tantalum 470uF Flat

This little model was never going to be straight-forward to get decent sound into, but we took the plunge... this one is a TMC weathered edition.

From the factory, it is neatly put together with sunken lighting boards and 6pin DCC socket. Very little room for anything more than a small standard 6pin decoder though.

Mark the direction of travel that we want to work with, by scraping an arrow on the chassis sides.

Disassemble, removing everything so that we can mill the top of the chassis - where we plan to fit an MX660 PCB sound decoder.

We mill off the top of the chassis creating a recess a little wider than the MX660 the full length of the tall part of the chassis. As deep as we dare go - the retaining screw goes across near the top, so we leave just enough metal to allow the screw to thread through securely.

Note how the insulating divider on the screw sits above our milled area - once we have everything back in (motor etc.) we carefully grind that visible edge down so that we have a flat surface, and test that the MX660 sits flat enough for the body to go back on.

Put down some electrical tape the full length of the milled area, and then some thin double-sided tape to hold the decoder in position. Pop the MX660 on top, and test that the body goes back on flush.

Fits nicely, so we can begin wiring. For the lighting boards, we decide to prise these out and replace the wires with our own new wires, using more standard DCC colours (blue for positive, white for the white lights and yellow for the red lights). We use ESU decoder wire as it is finer and more flexible than most. We'll have independent whites and reds on this model, so we solder the lights accordingly to the MX660's function output pads.

Put some electrical tape on the section where the original DCC socket board was, which will be for our speaker, then solder on the red and black pickup wires - we do this at both ends - reds on the right, and blacks on the left.

Also solder the orange and grey motor wires. After doing this, a quick test on the track should prove the motor control and the directional lighting.

On the SugarCurve6 speaker, bend the tabs back, cut short, and solder purple wires.

The speaker sits on the tape we put down earlier, but be sure the terminals cannot touch anything metal. Solder the other ends of the speaker wires to the decoder, and secure the speaker in place with a strip of tape. Time to test that the sound also works.

We can also put the body back on and prove that everything fits comfortably. In fact, most installers would probably stop here, and say it is a job well done, but we do like to push the boat out, so decide to open it back up again and add a little stay-alive.

With a little fettling, there is room in the fuel tank directly beneath the motor for a LifeLink PCB and 2x 470uF flat Tantalum capacitors. All insulated properly up, these sit flush in the tank, and a small channel is created to feed the wires up, connecting to appropriate +VE and GROUND pads on the MX660.

2x 470uF is enough to notice a considerable improvement in reliability of running, and far less frequent stalling, so well worthwhile doing.

So, the final result, back together and running nicely on the track test...

Please note that these guides are provided as useful resources for you, as-is. YouChoos cannot be held responsible for errors in the information, or for any damage caused to your models or equipment if you choose to follow any of the steps detailed here.