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Heljan OO GWR Diesel Railcar

Example 1: OO Heljan Railcar rewired for PluX22

Kit: ADAPLU; MX645PluX22; IceCube28X18X08; SuperCap17000uF

It seems that we are being showered with GWR Diesel Railcar models at the moment! Heljan's OO model is very nearly identical to its' large O gauge sibling in terms of the electrics, so we have the same problems of 21pin standards for lighting (or lack of standard!).

An MX644D or MX644C will simply plug in and work the motor and some of the lighting features, but you will be without other lightig features because of the varying 'standards' for the 21pin interface. The model is designed to accept a 21pin decoder with the latest RCN121 standard of which there is currently no Zimo sound decoder to support this.

Therefore we need to swap the 21pin board in the model with something else in order to support all of the lighting features. Our first example puts in an ADAPLU board which has a PluX22 socket. The nice thing about PluX22 is that it is a proper 'standard' with no ambiguity. All lighting outputs are expected to be full power (also known as 'open collector') rather than 'logic level'. We like PluX22!

So, we remove the PCB from the model, cutting off all the plugs and marking the wiring so we know what is what. Some simple tests using a battery confirm the lighting wires. To gain the maximum height for the kit, we chop down the original PCB screw mounts so that a decent 8mm dual IceCube speaker and SuperCap can sit on the bottom, with an ADAPLU board laying on them.

The ADAPLU is actually a booster board, which is a bit overkill for this model, since it won't be drawing that much power, but we chose it becasue the non-booster version (ADAPUS) is longer, and won't fit in the space!

Methodically transfer the model's wires to the approproach solder pads on the ADAPLU.

Optionally remove the switch bank from the model completely, as it will be redundant anyway.

Example 2: Hard-wired MX645

Kit: MX645R hard-wired; IceCube28X18X08; SuperCap17000uF

An alternative approach is to simply hard-wire an MX645 into the model, so no board. Note that because the model has 9 lighting features, and the MX645 only comes with 4 lighting outputs pre-wired, you'll need to solder an additional 5 wires to the decoder. YouChoos can do this for you before shipping for a nominal charge, if you're not comfortable doing it yourself.

Again, like the PluX approach, you must be methodical in transferring wires from the model to the MX645, testing each pair to ensure you know which wires relate to which lighting feature. No additional resistors are required since the model has its' protective resistors alongside the LEDs themselves.

Overall, this hard-wiring approach is our preferred method since it requires less kit, meaning it is both cheaper and more compact.


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.

A bit of YouChoos poster art for your enjoyment!