It’s time to finish a digital conversion of a train that had been pending since…2012. Yes, the Lufthansa Airport Express BR403 “Donald Duck” is now fully digitized, with bells and whistles!

A long time awaiting

The first article I posted was in 2012, just after I got this old model from Lima as a second-hand item. See here the original post. Since then, I got a bit better at DCC conversion. I got used to adding sound, which you may have noticed on the blog. I also more and more get used to replacing motors with coreless motors, especially on older model where the motor is close to end of life. Well, this unit got the full treatment:

  • Digital conversion with sound
  • Custom, power-transmitting magnetic couplers between cars
  • Interior lighting in all coaches, each with its own decoder
  • New coreless motor for the engine car

Cars with full digital capabilities

This model from Lima was old. Couplings where old style, non standard, hook couplers. Wheels hadn’t been planned for power feeding. All 3 coaches (including the dummy engine) where fitted with power feeders from the axles, as I had described here. Also, the new thing since 2021. I started using a 3d printer, and am still learning. Inspired by the excellent magnetic couplers from the company Peho (which are rather hard to find outside of Germany), I printed and made my own magnetic couplers. Each with 2 wires, so that the power is distributed along the entire train at all times. Each car was fitted with a Doehler & Haass FH05B function decoder, and with additional capacitors to alleviate even more any power interruption.

Power feeder and 3d printed coupler visible

Interior lighting

3D printed magnetic coupler


A whole new engine

The motor was old. But thanks to the cheap coreless motors from, available in many online stores now, I managed to install a whole new motor. A motor holder was designed, using the excellent website tinkercad, then printed, and voilà. The only thing that missed was the decoder. I didn’t want to solder one, so instead, I installed a Next18 socket directly on the motor. This way, I can even change the decoder in the future. For now, I am fully satisfied with the Doehler & Haass SD18A. In fact, I tested an ESU Loksound Micro v5, and it worked very poorly with the micromotor motor. Added to this some extra capacitors, interior lighting of course. And voilà, the engine is ready. The only thing I’d have done slightly differently is maybe choosing a bigger motor than the model 0615S, which sometimes has trouble and lacks a bit of power.

New micromotor

New micromotor

Bench tests

Next18 connector

Other than that, I know have a fully digital train, that – for now – has never been release again in N scale since the 1990s! Have a look at the video at the top. What do you think?