Rebuilding DSB train set with a NoHAB diesel, Märklin 28461, to digital with Märklin 60901 conversion set

Updated 12.01.2014

This train set is a nice one with a yellow NoHAB and three cars meant as workshops car for crane 147.

Märklin 28461 locomotive

I wanted to achieve two things with the conversion; one was to convert the locomotive from Delta to "full" digital, the other was to install light in the workshop car.
As the locomotive has a drum collector motor (DCM), several conversion sets from Märklin may be used: 6090, 60901, 60921 and 60760.  All these have the same motor, but different decoders.  6090, 60901 and 60921 are not available any more.  these sets had different decoders.

Today I would have used a 60941 motor conversion set and a mLD decoder set 60962.  See dcm conversion sets.
60760 has a simpler decoder, which has an unofficial output (f3), that may be used for the relay mentioned below.

The inside of the locomotive after the conversion.  The photo shows the new high propulsion motor, the decoder and the relay for the interior light in the connected car.  The small lamp on top of the motor is just for fun; I had to use the f2 output from the decoder for something.

The motor installation is pretty much straight forward.  Remove the old motor from the motor bogie.  The bogie must be separated from the locomotive chassis.   Before installing the new motor parts from the conversion set, make sure that all the mechanical part works perfect.  I clean parts like the motor bogie with a dish washing detergent and as warm water as I can handle (not very warm, according to my wife) and an old toothbrush. Remember to remove the small sponge over the inner (or LH) armature bearing.
The motor from the 60901 conversion set fits perfectly in the motor bogie.

The similar motor in the another NoHAB.

After washing, rinse carefully with warm water.  Wipe and blow off all the water.  Carefully oil all the rotating parts.  Do not use too much oil, only very small amounts are required.  Make sure that everything rotates perfectly.  Install the new motor.  Select the armature (rotor) with the same number of teeth as the old one.  That should be eight. Only one of the brush plates will fit.  Before installing the brushes, test again that everything rotates perfectly.

I installed the 60904 decoder in a decoder holder, Märklin part no. 258820, where the old Delta unit used to be.

The functions:
f0 = three white front lights changing with the direction
f1 = interior light in the connected cars, via relay
f2 = light behind the driver's cabin, end 2, 28 volt
f4 = acceleration and braking delay off

Light control with a relay:
In digital operation, the track current is square pulses, approx. 22 volt.
If a bulb, controlled by the decoder, is connected directly to the locomotive or car chassis, it will flicker according to the signal pattern from the digital signal.
There are two ways to avoid this:
Either insulate the bulb from the chassis and feed it with the regulated + from the decoder, orange wire.  This requires two wires to each connected car.
Or feed the bulbs with track current, via a relay.  This way only one wire is required to each car.  The bulbs are connected to chassis in each car.

The cars:
There are one wire running from the locomotive, through the generator car, and to the workshop car:
A brown/red wire: Current to the interior light, from the pick-up shoe via a relay.

The generator car from underneath:

This image shows the simple modification.  A brown/red wire runs from one coupler pocket to the other.

I have made small contact tongues in each pocket.  This is the front end, with the current conducting coupler rod, Märklin no. 7319.

This is the rear end, connecting to the workshop car.  The contact tongue is bent around the roof of the coupler pocket.  The same kind of contact tongue is used on the rear coupler pocket on the locomotive.

The workshop car is already prepared for Märklin's current conducting couplers.

The additional parts I have used to upgrade my Märklin 28461:
Märklin no. Pcs. Description
60901 1 Digital high performance conversion set for dcm motor
258820 1 Decoder holder
7319 2 Current conducting coupling (one set 7319 contains 10 couplers)
7330 1 Interior light set for the workshop car
- 5 28 Volt T1 bulbs for white front lights and interior lights in the locomotive

Wiring diagram for 28461: