The Dapol N Gauge LNER A4... installation guide for DCC sound using Zimo MX648 and full-sized SugarCube9 speaker...

When removing the tender body, and uncoupling the drive-shaft from the loco, you'll need to also unscrew the 2 wiring screws underneath the rear of the loco as well as one end of the joining bar - this will allow you to completely separate the tender from the loco, which will make handling of the model much easier.

Next, remove the 6-Pin DCC circuit board and carefully file down the mounting points where the socket was attached - the aim being to make as much room as possible. Below you can see in the 2nd picture that we've also chamfered the back of the motor housing to an angle which helps make space for wires to travel - probably not strictly necessary, but will make clipping the tender body back on later a bit more comfortable:

We plan to use a full sized Zimo SugarCube speaker and the MX648 sound decoder. The decoder is too long to fit behind the motor, so we have to aim to place it above the motor instead. As it stands, there is not enough room, so the coal load will be carefully chopped out making a rectangular hole to match the MX648 size:

Test fit the decoder through the hole now to ensure that the body will easily clip back on without any undue force:

To make a better seal, we've peeled off the enclosure from the SugarCube speaker, removed the sticky gasket, filed the enclosure down just a tiny bit (no more than 1mm), and reattached the enclosure to the speaker using a thin rim of super-glue all the way around the perimeter. We then use a small dab of super-glue to fix the enclosure-side of the speaker onto the chassis. There should be plenty of clearance above the wheels if you filed down the old DCC socket mounting points as shown.

Shorten the decoder wires, solder everything up (purples to the speaker, red + black to pickups, orange + grey to motor) and lightly put the decoder on the top of a small piece of double-sided sticky pad (will have to adjust the position a little once the tender top goes on anyway to match the hole we made in the coal load).

Fit the tender body back on, which should clip on fairly easily, just adjusting the decoder position as necessary.

Cover the decoder with a thin membrane of double-sided tape, ensuring that it covers up to the edges of the coal load - needs to be fairly well covering as we will be adding glue onto the top before adding the coal ballast, and we don't want it leaking and running through around the decoder down to the motor!

Using a fairly gloopy thick glue like UHU, apply a few drops onto the top of the membrane and spread it evenly and thinly across the whole coal load area. When you are happy with the covering, sprinkle a thick layer of crushed coal ballast (we used Woodland Scenics coal ballast here, crushed in a mortar and pestle until quite fine) over the glue, ensuring the glue doesn't spill down the tender body sides, and lightly press on with a clean finger. Shake the loose coal off, repeating with an extra drop of glue and ballast if it hasn't covered to your satisfaction.

Wait for the glue to dry overnight, reattach the tender to the loco, and you're all done!

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