Simple install using MX660 Drop-in sound decoder

Kit: MX660; SugarCurve7; SACC16 with 2x 330uF flat/wide Tantalums

The MX660 is closer in size/shape to the original factory PCB in the B4. Hopefully this will help in our wiring of the firebox glow LEDs in particular, as it will be easier to avoid the wires going near the fly-wheel. The MX660 also gives us the benefit of not requiring any resistor for the LEDs as the outputs are low-voltage, so simpler, and less components to squeeze in. The final benefit of the MX660 is how thin it is.

We snip off the rear pair of PCB supports from the model and use some thin double-sided tape to help secure the MX660 in place while we wire everything up. The underneath of the MX660 are given a protection of Kapton tape too.

Now we connect the motor wires and the pickup wires - we just reuse the original wires from the model, trimmed a little for neatness.

The 3 wires from the firebox LEDs are connected to the MX660, using the convenient AUX pads at that end, so no need to take the wires close to the fly-wheel. Some re-mapping of the B4's project is required to get the right outputs to operate like this, but it is a simple job - ask YouChoos to do this for you before shipping the decoder if you like!

The SACC16 stay-alive board is trimmed (the outer-most section removed to shorten the overall board). We solder a flat/wide 330uF Tantalum to each side.

The speaker and stay-alive are carefully protected from each other with Kapton tape, and stuck together with a little pad of thin double-sided tape. This should all fit into the boiler as a little unit.

The end of the motor shaft is trimmed to ensure that it doesn't snag on the speaker/stay-alive up in the nose.

We then wire up the speaker and stay-alive to the appropriate connections on our MX660, and give eveything a little test before reassembly.

All done, with some light weathering 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.