Bachmann OO LMS 1F Tank... a popular model that can take a Zimo MX648 decoder and SugarCurve7 speaker despite its' tiny size, just about squeezing decoder and speaker in the boiler, with hard-wiring and a minor chassis modification.

Remove the 6pin DCC socket board, as well as the resistors and suppression capacitors from across the motor. Grind the nugget of metal flat at the very front of the chassis (this is where the decoder and speaker will sit).

We have removed the heat shrink wrap from the decoder, and taken away any wires we are not using (kept green for firebox glow which we might add later). We have also added an extra grey wire in case we want to add a stay-alive too (SACC16 will go in with the decoder/speaker, and some Tantalums can be put under the roof of the cab, tucked fairly neatly out of view). Wrap decoder in Kapton for protection.

Optionally, drill open the base of the chimney - this improves volume a little bit as it provides somewhere prominent for the sound to escape, instead of through the bottom. Connect red+black pickup wires and orange+grey motor wires. MX648 decoder sits on the chassis with SugarCurve speaker on top.

The finished article, with custom weathering by YouChoos too...

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.