Heljan O Gauge Class 25 with MS Sound

Kit: MS950 + LOK950K; YLR603010 3W speaker + YLR302815 2W speaker

First off ensure your loco performs in DC, ideally has been run-in and all the lights etc. checked for correct operation. For this model the front/rear Red lights are switchable by a hidden switch underneath one of the cabs. So if initially they appear not to work search for the switch.

Using the foam from the transport box to prevent damage to any detail remove the body shell by removing the four cross head screws located behind the rear of the bogies up against the fuel tanks. Gently pull the body shell off and set aside the chassis being careful not to stretch the wires between body and chassis. It is wise to keep the two parts together to avoid confusion of where goes what later.

Compare to Figure 1 if the PCB is the same. We have to replace this board to enable the Zimo MS950 to be installed. You need the Zimo LOKPL 950K Locomotive adapter PCB connection board with screw terminals.

Next using pen and paper record each wire colour and function on the original PCB as we need to disconnect all wires and without any notes it will be hell of a job to sort out.

Once wires recorded and removed the original PCB can be removed by unscrewing the small four cross head screws at each corner. As the combined Decoder and Adaptor board are quite chunky in height, I inverted the support board which also enabled the use of four self tapping screws to hold the Adaptor board secure. This gives more room between the decoder and inside roof of the body shell. See figure 2.

Using your notes and the screw terminal designations of the LOKPL950K connect each wire so it looks like Figure 3. I advise that you connect up one function at a time to prevent disasters and test each one out before moving on. This is especially important when connecting up the two motor leads as it is easy to do it wrong so the motors turn in opposite directions! The plug for the Fan needs to be removed to connect to the Adaptor board terminals.

To fit the speakers you have to be creative. The smaller speaker I used double-sided tape to secure it to the top of the gear tower. At the other end I was lucky to use a piece of hard foam packaging to form a bridge to go over the mechanism which I glued to the chassis and used double-sided tape to hold the speaker. See Figure 4.

Photos and notes courtesy of Allan Jones

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.