Märklin conversion sets  for Drum Collector Motors (DCM)

Updated 11.05.2013

The DCM is recognized by one carbon brush from each side, connected to a drum shaped collector.
In a locomotive it looks like this:

This is from a Märklin 3106, including the electro-mechanical reversing unit.
The white motor cover also came in black.

The conversion sets:
There have been five different conversion sets for locomotives with the DCM motor.
Set motor decoder Remarks
6090 5-pole
high power
c90 No longer produced by Märklin
60901 c91
60921 mfx
60760 fx  
60941 none A decoder must be bought separately
The five conversion sets are identical when it comes to the five-star high power motor itself.  The big difference is the digital decoder.

The parts in a 60760 conversion set:

Basically, only the decoder is different form one set to another

The new motor,
installed in Märklin 3084, a Br 50 tender locomotive:

The c90 decoder in 6090:

The photo shows the 6090 decoder without it's plastic cover.  The pink wire is not a part of the decoder.

The c91 decoder in 60901:

This photo shows the c91 decoder without it's plastic cover.  The lamp is not a part of the decoder.

In the 60901 it was (not produced anymore) a so called c91 decoder, with a row of eight switches (so called Mouse Piano) to set the decoder address and two potentiometers to adjust the maximum locomotive speed and the acceleration/deceleration time.  The decoder receives data from the digital train controller, one way communication only.  With a Märklin control device you may select between 80 locomotive addresses.  The decoder dimensions are 36 x 21x 9 mm.  If required, it fits into a holder 258820.

The mfx decoder in 60921:

In the 60921 conversion set we find a mfx decoder.  It means, among others, that the decoder is adjusted from outside, from the train controller.  You can set a lot of things, like the address (if you use a Delta controller or the 6021 Control Unit), the maximum speed, which can be set rather accurate, the acceleration and deceleration time can be set individually and you have some control of the different functions of the decoder.
If using The Märklin Systems, either with the Mobile Station or the Central Station, the decoder is reporting itself to the control system, two way communication.  It is not necessary to set an address. The decoder dimensions are 22,3 x 15,5 x 5,5 mm.  If required, it fits into a holder 456200.  This decoder is wrapped into a sort of rubber tube in the conversion sets.

The fx decoder in 60760:

In this case the noise suppressors (inductors) were soldered directly to the decoder.  Normally a blue and a green wire is soldered here.

The decoder in conversion set 60760 is a simplified decoder compared to the mfx decoder in 60921.  It is adjusted from outside, with the train controller, e.g. 6021, a Mobile Station or a Central Station.  Acceleration and braking delay, as well as maximum speed can be adjusted.  The decoder has 14 speed steps and outputs for forwards and reverse lamps as well as an orange wire for the regulated plus. If required, the decoder fits in the holder 456200.  This is a "receive only" decoder, one way communication.

The Märklin conversion sets 6090, 60901 and 60921 are no longer available from Märklin, and are replaced by a separate motor set and a choice of separate decoders.

The new motor conversion set, 60941:
The conversion set 60941 is the motor and small parts only.  I think these parts are identical to the motor parts from 60901 and 60921, but I have not seen them yet.  The decoder of your choice must be bought separately.  There are four different Märklin decoders types to choose from:

The new decoders:
60942, mLD, multi protocol decoder (mfx, MM1, MM2 and DCC) with an amplifier board, six function outputs
60962, mLD, multi protocol decoder (mfx, MM1, MM2 and DCC) with wires and an 8-pole NEM connector, four function outputs
6094?, mSD, multi protocol sound decoder (mfx, MM1, MM2 and DCC) with an amplifier board, six function outputs and speaker
6096?, mSD; multi protocol sound decoder (mfx, MM1, MM2 and DCC) with wires and an 8-pole NEM connector, four function outputs and speaker

The sound decoder's number last digit: 5 is for steam engines, 6 is for diesel and 7 is for electric locomotives.
The mSD decoders 60948 and 60949 has special amplifier boards suited for the 36-series Hobby locomotives with bogies.  60948 for diesel engines and 60949 for electric engines.
The mSD decoder 60940 has a 21 pole mtc connector, to fit into locomotives with a factory fitted mtc21 amplifier board.

See this Märklin web site for detailed information.

Märklin DCM conversion sets consists of a number of parts:
Part name Conversion sets Märklin
part number
6090 60901 60921 60760 60941
Decoder, c90 with DIP-switches 1          614090
Decoder, c91 with DIP-switches   1       603617
or 60902
Decoder, mfx     1     611298
or 60922
Decoder, fx       1   121341 ?
Rotor 1 1 1 1 1 386820
Field magnet 1 1 1 1 1 389000
Motor cover 1 1 1 1 1 386940
Brushes 2 2 2 2 2 601460
Noise suppressor (inductor) 2 2 2 2 2 516520
Screw M2,5x12 2 2 2 2 2 785140
Soldering lug 1 1 1 1 1 231470
Capacitor 2 2       600760
Rubber tube 2 2 2 2 2 787570
Tool to adjust the decoder   1       610080 The photo shows some of the small parts that came with 60901 and 60921, like the
noise suppressors (inductors) and rubber tubes.  The brushes for the motor and a
soldering lug for ground connection also comes with the set.
Manual 1         ?
  1       608899
    1     611488
      1   101677
        1 174810
No warranty for correctness!

Installation in a locomotive:
A number of locomotives may be converted without any problems, but some require additional work.  If you have some mechanical and soldering skills, it is normally no problem to install the conversion set into a locomotive.  The locomotive must of course be in a good mechanical condition prior to the conversion.  If you don't have the skills yourself it is recommended to leave the work to professionals, like your Märklin dealer or the Märklin Repair Service in Göppingen, Germany.

The decoder functions:
Function Direction 6090 60901 60921 60760 Remarks for 60921
f0 forward yes, changing with direction On the mfx decoder in 60921 these selections
can be done with the Central Station 60212 or newer.
In addition to the acceleration and braking delay,
this decoder also have a shunting speed
setting, normally also controlled with f4.  This
may be set to e.g. f3 with the Central Station.
Also the output type and intensity can be
selected, like light, flashing light, smoke unit etc.
reverse yes, changing with direction
f1 forward -yesyes,
one direction only and/or
on/off with start or stop
may be selected.
f2 forward -yes -
f3 forward - - - unofficial function
output, no wires installed
f4 forward - acceleration and
braking delay cancelled
Shunt speed and
delay, may be separated
acceleration and
braking delay cancelled
Adjust-ments bothmaximum speed, by potmeter
acceleration and braking delay, by potmeter
maximum speed, from controller
acceleration and braking delay, from controller

A Central Station 1 screenshot:

The left half shows an mfx decoder, identical to the one in the 60921 set, the right half shows a c91 decoder, like the one in 60901.  The different functions are indicated far left and far right in the picture.  From the top we have f0, front head lamps, f1, for instance interior light front end, f2, for instance Telex rear end, f3, shunting speed (not on the c91) and f4, cancelling the acceleration and the deceleration delay.  The function order and position (which key to press) may be altered with the mfx decoder, but are fixed with c91 decoder.

Motor current at different voltages:

The X axis is the voltage, from 1 to 18 Volts in 0,5 Volt steps.
The Y axis is the current in milliampére.
The motor started at 3,00 Volt at increasing voltage, stopped at 2,50 Volt at decreasing voltage
Blocked motor at 10,00 Volt was 983 mA
Test locomotive was a V36 from train set 2848.

Some photos from the installations:

Märklin 28502 RCT 36 274, using the 60921 conversion set:

Märklin 3366 DB 152 motor, using 60921 conversion set:

The plastic "shelf" glued to the magnet is not an original part for the conversion.

Märklin 3145 SNCF Y 50, using 60760 conversion set:

There are many internet sites regarding this kind of conversions and how to solve the difficulties.  Just search for Märklin 6090, 60901, 60921, 60760 or 60941 conversion.