Converting Märklin 3309, DB 85 007, to digital using the mfx conversion set 60901 and a sound decoder

Updated 16.05.2013

The mfx conversion set 60901 s no longer produced by Märklin.  It is replaced by a motor kit, no. 60941, and a separate mLD decoder 60942 (including a circuit board with six function outputs) or mLD decoder 60962, with wire ends and four function outputs. mLD means märklin Locomotive Decoder.  See the Märklin web site for detailed information.
The mSD (märklin Sound Decoder) 60947 (with the circuit board) or 60967 (with wires) may of course also be used, if there is space for the loudspeaker.

Märklin 3309 locomotive, DB 85 007:

The locomotive has a Drum Collector Motor (DCM) and an electronically controlled mechanical reversing unit, which also controls the Telex couplers, and constant light intensity regardless of the driving speed.
I am rebuilding it to digital, with an mfx sound decoder.  This fantastic locomotive deserves the best.

Unfortunately I have no photos of the locomotive inside before disassembling.

The locomotive inside after the conversion:

This is before the final interior light installation.

Very simple to explain: remove everything.  After removing the pick-up shoe, carefully remove the plastic part under the locomotive, including the brake shoes.  Unsolder the wires to the pick-up shoe contact and to the ground point. Unscrew the two screws on the motor cover, the screw holding the electronic unit and the plastic screw holding the reversing unit.   Then it should be possible to "lift out" the reversing unit, the electronic part and the motor in "one piece".  I carefully pack these parts in a small plastic bag and store them.
I also remove the front and rear leading axels and couplers, to be sure of no accidents during the work.

Cleaning the locomotive's rotating parts
The next step was to clean the locomotive thoroughly, to remove all dust and old oil.  I use dish washing detergent, an old toothbrush and as hot water as I can handle.  After cleaning and brushing, I rinse very well in hot water.  I remove the friction tyres before cleaning the wheels.  Then carefully oil the rotating parts..

Installing the motor:
No problem at all.  Install the new magnet and enter the rotor.  Be careful to hit the inner bearing.  Install the motor cover and secure it with the two 2x12mm screws.  Add a tiny drop of oil on each rotor end.

Installing the decoder:
I decided to use a ESU V3,0 M4 sound decoder, due to it's programmability and it's mfx protocol, and that ESU has a sound project for a three-cylinder steam locomotive.  It can be installed on an amplifier board, with six function outputs.  See below table.
I have replaced the wires on the amplifier board, as I wanted to use Märklin colour codes.

Before selecting this decoder I installed a Märklin 60931 mfx sound decoder with four function outputs; f0-f and f0-r for the lights, f1 and f2 for other functions.  I connected f1 to the smoke unit and f2 to both Telex couplers.  If both f1 and f2 was on, the decoder was overloaded.  I saw that I needed more outputs.  

The decoder functions:
function direction Item
f0 forward Light front end
rervers Light rear end
f1 both Smoke unit
f2 both Light, driver's cabin
f3 both Front Telex
f4 both Rear Telex
both Sounds, shunt speed
acc/dec delay off
For further details, see below function table.

For space reasons I have chosen to use a 20mm speaker with a square chamber, which came from a Märklin mfx sound decoder set, no. 60933 (used in my 37292).  This speaker has 100 ohm impedance, the same as the speakers suitable for the ESU V3,0 M4 sound decoders.

If not using the speaker that comes with a conversion set, check the impedance of the conversion set's speaker before connecting the new speaker.  The speaker impedance may be different from one decoder to the next,  Some have 100 Ohm, others may have 4 or 8 ohm speakers.  The different impedances are not interchangeable and may damage the decoder if it's wrong.
The impedance is normally printed on the speaker.  If not, use only the speaker that comes with the decoder.

To be able to install the speaker where I wanted, I had to do some modification the the speaker chamber.
This was to be able to install it far enough forwards not to interfere with a wall inside the locomotive body.
The wall fits between the speaker and the motor.

I also had to cut a groove in the chamber, visible just below the white wires, to assure free movement of the articulated locomotive chassis.

The speaker is glued into position, and the decoder is installed.
The wires going backwards in the locomotive is secured with black tape.
I also had to grind off a bit of the top of the speaker chamber, not to hit the inside of the locomotive body.  At the time of the installation I did not have a good file for this purpose, so I used my soldering iron (not the tip) to melt away some of the plastic.  It doesn't look good, but it does the job.

The amplifier board for the decoder is glued to the bracket for the old reversing unit, as far down as possible.
I had to cut off a bit of the board, not to hit the inside of the locomotive body.
The noise supressors for the motor is glued to the chassis, one on each side of the decoder.

Front and rear lights:
I use the original bulb sockets as they were already insulated from the chassis.  The original bulbs, 600190, is for 1,9Volts only, controlled by the electronic unit for the reversing unit, so I use bulb 600100, including a 100 Ohm resistor to reduce the light intensity.

Front light:
The electronic unit used to be fastened with the screw in the photo.
I have made a small circuit board, which serves these purposes:
1. distribution of the red wire from the pick-up shoe, so I don't have to remove the big plastic part under the locomotive if I wish to make some changes.
2. distribution of the brown ground wire.  The ground wire is connected to the motor, to the front part of the chassis and to the decoder.
3. distribution of the orange + wire to the front Telex, to the rear of the locomotive and the resistor to the front light.

Rear light:
The orange wire is connected to the bulb socket via a 100 Ohm resistor. The input to the resistor serves as a distribution point to the rear Telex and to the interior light.

The rubber hose is to prevent light spill, especially downwards.

Cabin light:
A 28 Volt T1 bulb is used for the cabin light.
A two-pole bulb holder is glued to the rear wall of the motor, next to the magnet.  A bulb with isolated wires are installed on top of the motor.

I am not sure that this will be the final solution.

Part list for the conversion:
Part number Pcs. Description
60901 1 Digital high propulsion conversion set, motor and small parts only
600100 2 Light bulbs for screw socket
207648 1 Speaker chamber, square From a Märklin
60933 mfx sound
conversion set
207649 1 Holder for speaker
?? 1 Speaker, 100 Ohm 0,5 W, 20 mm
ESU 62489 1 Loksound V3,0 M4 sound decoder, 21 MTC, programmed with
ESU sound project file 62402, three-cylinder steam locomotive
ESU 51968 1 21 MTC Amplifier board with f3 and f4 outputs
- 28 Volt T1 light bulbs
- 1 2-pole bulb holder, cut from a SIL connector
- 2 100 Ohm resistor for front and rear lights
- 1 Home made experimental circuit board, 3 rows, 4 holes

My setting of the decoder:
Decoder settings, 3309 Default Mine
Analog settings:
  Enable analog mode check <
Starting voltage 15,500 <
Maximum voltage 25,500 <
Control settings:
  Swap directions uncheck <
Max. speed 255 95
Min. speed 3,000 1
Acc. time 7,000 10,000
Dec. time 5,250 10,000
Forward trim 1,000 <
Reverse trim 1,000 <
Motor settings:
  Motor PWM-frequency:
Low frequency uncheck <
High frequency check <
Load Control, 5* Märklin motor:
Reference parameter 12,500 <
Control parameter K 32 <
Control parameter I 24 <
Control influence 255 <
Special options:
  Preserve direction check <
Persistent acceleration uncheck <
Persistent speed check <
Persistent functions check <
Sound settings:
  Volume 255 160
Driving Sound Rate:
At min. speed 1,000 <
At max. speed 1,240 <
Random Sound:
Min. gap 30 10
Max. gap 50 40
Steam Locomotive:
With speed sensor uncheck <
Without speed sensor check <
Steam chuff at speed 1 50 <
Steam chuff at speed 2 35 <
Braking Sound:
Threshold 14 <

The 3309 DB Br85 function table:
3309 DB 85 007
mfx sound Light Smoke
Telex Driving
Sound Sound Sound Sound Shunt
funct. dir. front rear front rear short long
f0 forward 3                                
reverse   3
f1 both     on                            
f2 both       on                          
f3m both         up                        
f4m both            up                      
f5 both             on                    
f6m both               on                  
f7m both                 on                
f8 both                   on              
f9m both                     on            
f10m both                       on          
f11m both                         on        
f12m both                           on      
f13 both                             delay off    
f14 both                           off  
f15 both                                 on
Stop forward                                  
Drive forward                                  
   f??m = momentary function

Screenshot from the Central Station 1:

The left part is my Märklin 3308, DR 85 006, which is converted to digital with a Märklin 60901 conversion set.  One day it will get a Märklin 60962 multi protocol decoder.
The right part is my Märklin 3309, DB 85 007.

The 3309 wiring diagram:

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