Heljan O Gauge Class 33 Diesel with Zimo Sound

Kit: MX699KS; YLR603010; Cab Lights; ModelU Figures

One of Heljan's more recent additions to its' vast 7mm diesel range, the Class 33 is excellent, here in DRS livery.

Basically, remove the factory PCB and put the MX699KS decoder in its' place (pretty much identical footprint). Remember to include resistors for the lighting, as the original protective resistors were on the board that is removed. Heljan have at last produced a model with almost standard DCC wire colours too, so less confusion!

Below we show the factory PCB removed, and the MX699KS in position.

The YLR603010 is the ideal indoor speaker to use here - loud enough, but not deafening, with a good quality output, especially as it can be placed directly in the fuel tank where the sound can escape properly. Really neat fit.

We did experiment with a 2nd speaker (YLR302815) underneath the decoder, where there is certainly enough space, but the acoustic effect didn't really work and the sounds ended up being boomy and echoy, loosing crispness, so we decided it was better with just the single YLR603010 in the fuel tank. Many other options are possible of course, but this we found to work very well, as well as being simple to do.

Just the process of insulating under the decoder, and working through the wiring, screwing them into the appropriate terminals of the MX699KS. We've given this model independent head and tail light control, as well as connection for the fan, and directional cab lights, so 7 outputs used in total. Let us know if you'd like this configuration, and we can alter your decoder before shipping.

Note the resistors, which we've put on the FA (negative) side for each output. Normally we prefer to put them on a split common output, but in this case it was neater to have them individual from the negative to save extra wire joins.

Remember that the motor and pickup wire colours are reversed for each end bogie, as per normal Heljan practise, so you'll have red from one end with black from the other for one side of the track, and vice versa for the other side. Similar for the motor - grey+orange one end, and orange+grey the other end (otherwise the motors will work in opposite directions!

The ModelU crew figures go in too...

Here's another one in green with similar kit, and weathering applied...

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.