Sonic Models N Gauge Large Prairie

Kit: MS500; SugarCurveTwist 3D Speaker (special edition); 2x 470uF Flat Tantalums

Sonic's Large Prairie is put together nicely. From factory, provides a 6pin DCC socket for a small right-angled standard decoder.

To gain access inside, carefully pull out the boiler stays, and a single screw at the rear allows the chassis to drop out.

Inside, the 6pin socket board and blanking plate are revealed.

We'll aim to put our little Zimo MS500 sound decoder on the cab floor, but it will be tight, so we remove all wires and add fresh wires just for what we need, with the wires facing in rather than away from the decoder. An intricate job, so lots of care required.

The factory PCB is removed and we use a couple of small squares of copper for the pickup connections.

For a simpler life, a MicroCube5 or 6 will fit up into the cab roof. However, we go for a bigger sound, using a custom 3D-print speaker - the same one we used for the Farish 3MT in fact. This is a 15x11mm SugarCube component, but on a transversely curved enclosure.

Belows shows how easily a MicroCube6 would have fitted in...

To make space for the larger speaker, we remove the cab roof and bunker top - a bit delicate to get off, but not as tricky as we expected!

Some minor removal of detail allows the bigger speaker to fit flush into the roof.

So, proceeding with the decoder installation, we have the pickup wires to our screwed-in tabs, motor wires direct to the decoder, 2 purples for the speaker, and we add ground and common positive (grey and blue here) in preparation for a stay-alive.

Wrapped in Kapton tape, the decoder sits on the cab floor. A little double-sided tape to secure it loosely in place.

A pair of flat 470uF/16V Tantalums are connected in parallel for stay-alive (optional).

There isn't quite enough height for decoder, Tantalums and speaker vertically, so we modify the metal bunker weight to allow for the capacitors to sit there instead.

Wrap the caps in insulation tape and secure those down - tight, but neat fit.

Carefully put the cab roof back on and check everything is flush. It is, but there is no room for messiness!

Sounds and runs fantastic with that kit though, so well worth a little additional effort.

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