The following scenarios must be distinguished for locomotive conversions:

• Analogue locomotives
• Digital locomotives without plug-in connections
• Locomotives with standardised plug-in connections

Further down on this page, we have documented various locomotive conversions for you in text and images, and we update these regularly.

Basic Notes on Conversion

• Always take photos of the locomotive before conversion, ensuring the wiring is fully visible. You never know when you might need them.
• Check if the locomotive works before disassembling it. It’s very frustrating to spend hours troubleshooting after a conversion only to realize the locomotive was already broken beforehand.
• Even during the conversion, it’s worth taking regular photos—this can help with troubleshooting and allows us to better understand what you’ve done when you reach out for support.

H0 Analog Locomotives (without standard plug)

For PluX22, we offer our own installation adapter with large solder contacts or screw terminals.

For an analog Märklin locomotive, you will find detailed documentation in the article Conversion of BR03.10 Märklin 3089 based on our CTC locomotive module M3.

The decisive criterion for selecting the locomotive module and choosing an installation adapter is the available installation space:

• For older Märklin H0 locomotives, this is relatively straightforward: Since the direction switch is removed during the conversion, its space can be used for the CTC module. The space is sufficient for the installation adapter, CTC locomotive module, and a 1000 µF buffer capacitor.
• In two-rail H0 locomotives, there is often insufficient space for both the locomotive module and the installation adapter.

G Scale Analogue Locomotives

Whenever there is sufficient space for the CTC-Lokmodul-G2, this should be your preferred choice. While the more compact combination of CTC-Lokmodul-M3 and CTC-Adapter für PluX22 with screw terminals is indeed smaller, it offers no significant price advantage.

We dedicated an article to the LGB classic “Stainz”: Conversion of LGB Stainz #2020 and #2021.

Using the CTC-Lokmodul-M3 and the CTC adapter for PluX22 makes installation significantly easier than with the CTC-Lokmodul-H0a shown in the article. Our Stainz is already in the workshop awaiting conversion, which will of course be documented.

Digital Locomotives Without Plug Connections

The conversion process is fundamentally similar to that of analog locomotives. However, attention must be paid to how the functions—particularly lighting—are wired. Often, there are already lighting circuit boards with a shared power supply connection and multiple control connections.

Whether there is enough space for the locomotive module can only be determined by opening the locomotive. However, there is a good chance that removing the old electronics during the conversion will free up sufficient space.

The old electronics often pose a puzzle. In most cases, I decide to remove the old electronics without inspection and only figure out how the lighting and motor function.

Note: Sometimes, the current-limiting resistors required for LEDs are not on the lighting board but on the main board or even the decoder. If you connect an LED directly to a switching output of the CTC locomotive module, the LED will burn out immediately.

Locomotives with Standardized Plug Connections

For standardized plug connections, we already offer matching locomotive modules:

• CTC-Lokmodul-21mtc for Märklin’s 21mtc.
• CTC-Lokmodul-PluX22 for PluX22.
• CTC-Lokmodul-M3 with a SUSI3-Classic socket in various versions for the plug standards PluX22, 21mtc, NEM-651 (6-pin), and NEM 652 (8-pin), as well as with open cable ends.

Installation Space:

• For PluX22 and 21mtc, the installation space for the decoder is defined in the standard, and our CTC locomotive modules comply with it.
• NEM-651 allows separation of the decoder and plug. Our CTC-Lokmodul-M3 cannot meet the installation space requirements for the decoder. Starting in autumn 2025, we plan to offer a locomotive module designed for N scale that will meet the NEM-651 specified dimensions of 20 x 10 x 4 mm.
• For NEM-652, the plug and decoder are always separate. The CTC-Lokmodul-M32 fits easily within the prescribed installation space of 31 x 18 x 7 mm.

Unfortunately, we cannot guarantee that manufacturers always adhere to the installation space specifications. In case of doubt, the only solution is to open the locomotive and measure or test, or possibly trim or mill away material as needed.

If you require modules for other standards, please let us know—we can then adapt our development plans to your needs.

Locomotives with DCC Sound Decoders

Instead of replacing an existing DCC decoder with a CTC module, you can also install the CTC module between the track and the DCC decoder. This is particularly useful if you want to continue using the sophisticated sound of your locomotive with CTC.

For instructions on how to do this, see the article Umbau PIKO BR 50 mit DCC Sound.

We also offer a “DCC” variant of the CTC-Lokmodul-M3 with cables and preconfigured specifically for this use case.

H0 Conversion Documentation

Märklin H0 Analog

These conversions were carried out using the now discontinued CTC-Lokmodul-H0a module.

Märklin H0 Analog PluX22

These conversions involve installing an adapter in the locomotive, which then allows the use of a CTC locomotive module with a PluX22 connector.

H0 Digital

H0 21mtc

H0 21mtc with SUSI3 Sound

H0 PluX22

H0 NEM-652

H0 with Sine-Wave Motor

Model Railway Conversion Documentation

Garden Railway Conversion Documentation

Garden Railway – Analog

Garden Railway DCC

Garden Railway with DCC Sound

Garden Railway with SUSI3 Sound

Conversion Documentation for Gauge I

H0m Conversion Documentation

H0m Analog