The Heljan / Hattons OO Beyer Garratt...

Carefully remove centre housing underneath as instructed in the leaflet that comes with the model. Be especially careful not to pull any of the wiring too hard, as it is quite spaghetti-like inside, and the wires are brittle!

Remove the boiler top to access the speaker area and remove the factory-fit speaker, which is not powerful enough to make it worth keeping, unless you fancy building a proper enclosure for it.

The Zimo SugarLump will fix into the old speaker's place with a double-sided pad, soldering to the provided contacts, or direct to the MX645 decoder. A stay-alive capacitor can also be placed inside the boiler - the standard 220uF/25v capacitor is shown here, but you could easily fit a larger one in - although probably not necessary as the model has good pickups and good weight.

NB Even better would be an IceCube18X13X12-1W speaker.

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.