The locomotive housing is hooked into the chassis all around with many tabs. To open it, I carefully bend the plastic housing outwards and then slide business cards between the housing and chassis so that the tabs do not snap back in. Once all the tabs have been levered out of their slots, the housing can be easily pulled up.
Since swapping the PluX22 decoder for a CTC-Lokmodul-PluX22 is a breeze, I started with the IR receiver this time. I removed the main board and then drilled a hole for the cable in the chassis:
The IR receiver finds its place next to the bogie where the slider is mounted:
Then I replaced the DCC decoder with the CTC-Lokmodul-PluX22 and plugged the IR receiver into it.
Initial test runs show that the locomotive either has no buffer capacitor or one that is far too small. Although the main board of the locomotive has a capacitor connection, it is not connected to the corresponding pins of the PluX22 socket. Therefore, I had to solder the buffer capacitor to the solder points provided for it on the CTC-Lokmodul-PluX22. Unfortunately, the cutout in the main board does not offer enough space for the usual 1000 uF capacitor from CTC, but a 470 uF capacitor was sufficient as well:
Note: After this conversion, the BR147 from Piko works so well that it has become the most used locomotive during CTC development.