Heljan O Gauge Class 40 Diesel

Kit: MX696KS (or MS950KS or MX699KS will also fit); YLR453520 speaker

Heljan's Class 40 diesel is similar to many of their other large diesel engines. Various choices for decoder, but in this case we've selected an MX696KS.

NOTE: be aware that wiring colours may be different from model-to-model, so check what yours has as you go. Also, these notes assume that there are resistors with each LED rather than on the original terminal adapter, so please check your model first otherwise you'll blow the LEDs if there are no resistors in those circuits!

Unscrew the 4 small screws holding the PCB and lift the PCB out of the way to reveal the space for the speaker. The housing will fit the YLR453520 - remove the 2 fixing lugs first and secure with BlackTack.

Carefully remove the wires from the PCB and mark the connections as you go. Join the orange wire from motor 1 with the grey wire from motor 2, and then the grey from motor 1 with the orange from motor 2 - this ensures that both run in the same direction!

Separate the decoder from the screw terminal adapter - note which way round they fit! Attach the speaker wires (red and black) to the terminals marked LS.

Attach the blue (common) wires for the lights to the first terminal.

Attach the 2 white wires and 1 purple wire to FLf and the 2 yellow and 1 green to FLr.

Attach the 2 red wires to the 5th terminal 'Sli' (track left) and the 2 black wires to the 6th terminal 'Sre' (track right). Attach the grey/orange wires from the motor - 1 pair into M- and the other into M+

The roof fan wires can now be cut away from the plug with the brown wire attached to the 4th terminal 'Fa5' (check what mapping you have on your decoder in case it differs). The purple common wire joins the 3 blue common wires in the first terminal.

The screw connector board can now be mounted with BlackTack in the space left by the original PCB - note that the screw holes do not match. Refit the decoder board - ensuring the correct orientation!

Photos and notes courtesy of Paul Rogers via Chester Model Centre.

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.