Converting a Trix® Re4/4II Locomotive to 3 Rail Digital

By: Mark Mervine

In 2001 Märklin® produced the Swiss Re4/4II in the red and cream Tee livery as item number 37343. This model has become a real collector’s item, is hard to find, and has become expensive. In 2008, Märklin® produced a two rail version of this locomotive as Trix® item 22148. After waiting to see if a three rail version would be produced in 2009 (to no avail), I decided to purchase a Trix® 22148 and convert it to three rail.

As the chassis and motor for the Trix® 22148 Re 4/4II is based off of the standard Märklin® Re 4/4II chassis, this turned out to be a pretty easy conversion. This article describes how I accomplished the conversion. In addition to the Trix® 22148, the parts needed for the conversion were as follows:

a) Märklin® #206370 pickup shoe

b) Lokpilot® v3.0 Digital Decoder, ESU® part number 52610

These parts can be obtained from your Märklin® and ESU® dealers.

An ESU® Lok Programmer® attached to a Personal Computer (PC) was used to adjust the decoder’s settings once the installation was completed, but this can also be accomplished with other devices (your Märklin® 6021 Control Unit or Uhlenbrock Intellibox). Other tools required for the installation were a soldering iron, wire cutter, needle nose pliers and small screwdriver.

Step 1 – Remove the Locomotive Body

The first step in the process was to remove the locomotive body. There is one retaining screw that is accessible when the locomotive is inverted and placed on a work surface. Access to the motor and electronics is available when the locomotive chassis is set upright. The picture below shows the Trix® 22148 chassis (bottom) compared to a standard Märklin® Re 4/4II 37XXX chassis (top).

(Click Images to Enlarge)


Photo by Mario Fabro

Step 2 – Replacing the DC Wiper with a Pickup Shoe

As seen in the photo below, the Trix® 22148 comes with a DC wiper instead of a pickup shoe on the non-powered bogie. This wiper will snap off allowing a Märklin® #206370 pickup shoe to be snapped onto the non-powered bogie.


Photo by Mario Fabro

Step 3 – Separate the Black and Red wires

The next step is to cut the black wire that is soldered to the red wire coming from the pickup shoe. The black wire will instead be soldered to the chassis ground.


Photo by Mario Fabro

Once this is done, loosen the circuit board enough to install the decoder. The Trix® 22148 circuit board has a standard NRMA 8 pin decoder socket. Remove the small circuit board that is plugged into this socket and plug in a Lokpilot® decoder. On my Trix® 22148, pin one was not marked, so I carefully examined the circuit board to determine which way to orient the decoder. The Lokpilot® decoder manual indicates that pin one is the one with the orange wire.

Step 4 – Testing

Before continuing, I performed a bench test. I placed the Trix® 22148 chassis with the new pickup shoe and LokPilot® decoder on a special programming track. I used my ESU® Lok Programmer® connected to a PC, to test out my progress and make sure all was working as anticipated. I then adjusted the acceleration and braking delays as well as the four CV’s as recommended for a Märklin® 5 pole motor:





All that was left to do was to re-install the body on the chassis, place the locomotive on the layout and enjoy the smooth operation of the 5 pole rotor and LokPilot® combination. Below is a picture of my converted Trix® 22148 pulling a set of tee cars on my layout.


Photo by Mark Mervine