Heljan O Gauge Class 25 Diesel

Kit: MX696S; YLR603010; YLR302815; SuperCap17000uF

Fairly typical design for Heljan's large O gauge diesels, the biggest difference with the Class 25 being that there is only a single motor with drive-shaft flywheels instead of a pair of heavier motors. Despite this, we still have limited height to play with for a sound decoder.

We begin the surgery by removing the model's screw-terminal PCB and trying an MX696KS for size. Unfortunately this is too tall with the decoder's screw terminal adapter plugged in, so we opt for a more unorthordox approach which is to just have the MX696S decoder (no adapter) and solder wires direct to the feet of the decoder itself. We recommend not doing this yourself unless you are a very confident solderer, but YouChoos can pre-attach the wires for you before shipping for a nominal charge.

A quick check was done here to make sure it would fit OK...

So, onto the re-wiring, methodically testing the wire pairs and connecting them to the appropriate feet of the MX696S.

Eventually all done, tested and wires tidied up.

The fan PCB needs to be repositioned so it is no longer above the decoder.

A YLR603010 speaker is stuck into the roof at the other end using BlackTack.

A YLR302815 speaker is mounted onto the bogie at the other end using BlackTack, being careful that it has good freedom of movement so the bogie can swivel without restriction.

Everything tidied up, and put back together.

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.