Rebuilding Märklin 3772, DB 212 225-7,  to digital with Märklin 60904 conversion set and 60932 mfx sound module

Updated 06.06.2013

Märklin 3772 was produced from 1985 to 1986, meant for the Märklin dealer's digital demonstration layout.
In 1985 and 1986 the transparent 3772 had road number 212 225-7.
From 1987 to 1989 it had road number 212 215-8.
Märklin 3757, DB 103 121-0 and Märklin 3774, DB 216 127-1, both with transparent body, was also made for this purpose, both from 1985 to 1989.

Märklin 3772 before modification:

Märklin 3772 after modification:

The locomotive inside before disassembling:

The locomotive inside after the rebuild:

Conversion parts:
For the conversion of the 3772 I used the Märklin conversion set 60904.  60924 is of course also suitable.  The only different between the two sets are the decoder; normal c91 digital decoder in 60904 and an mfx decoder in 60924.  In this case it did not matter, as I installed the 60932 mfx sound conversion kit.
The 60904 and 60924 conversion sets are no longer produced by Märklin.  Today I would have used the motor conversion set 60944 and the mSD (Märklin Sound Decoder) 60946.
I do not know the 60946 sound decoder, as I have not installed this new decoder type in my locomotives yet.

The 3772 has a Large Flat Collector Motor (LFCM).  Therefore the motor from conversion set 60904, 60924 or 60944 is required.

The removed original motor:

The motor installation requires some milling work, as it will not fit in the chassis.  Also the motor itself needs some filing.

First I removed the part indicated by the red rectangle, to fit the thicker magnet.  A small part, under the right red line, had to be removed to give space for the lower motor cover screw.  I did not find the correct color for the repainting.  The new surface after the milling is indicated in red in the below photo.

The bottom of the magnet must be filed off a little bit, to allow free movement of the bogie.  A cut-out must be made (lower arrow) to give space for the bogie part (upper arrow).  Otherwise it will hit the magnet at almost no turning angle.

Newer editions of this locomotive have the Drum Collector Motor (DCM).  Then the motor from the sets 6090, 60901, 90621, 60941 and 60970 will fit.  I do not know what kind of modifications this motor type requires, if any.

Decoder and speaker:
The decoder is installed almost at the same place as the original reversing unit.  It is installed in the holder 456200.  But - only almost.  I did a lot of thinking before coming to the final layout of all the parts.
First I installed the square house for the 20 mm 100 Ohm loudspeaker, glued to the chassis. I hade to make a small cut at the front lower LH corner of the speaker house, and also a small "step" at the rear end, to fit the motor housing. Next the decoder holder 456200 was glued to the speaker housing. I bent down the front "wall" of the decoder holder.
This speaker came with the 60932 mfx sound conversion kit.

The decoder functions:
See table below.

Inside the locomotive body there are some reinforcements.  One if these hits the speaker housing, so I had to make a small "cut" on top of  the speaker housing to create space for the body reinforcement.

Some more inside views:
The complete locomotive:

The rear end:

The only thing remaining is to find the correct parts to install close couplers. I have seen some information in an old Märklin Magazine (4/2002) and on some downloadable files from the Märklin website.  And, as this locomotive has a rather advanced and modern propulsion system, I think of replacing the front and rear bulbs with LEDs, three white in the front and to red in the rear.  If so, I will make a printed circuit for the LEDs, something like I did for the Märklin 00380, DB 38 1967.

My setting of the decoder:
Decoder settings, 3772 Default Mine
Analog settings:
  Enable analog mode check <
Starting voltage 7,300 <
Maximum voltage 23,000 <
Control settings:
  Swap directions uncheck <
Max. speed 255 60
Min. speed 4,000 <
Acc. time 7,000 11,250
Dec. time 3,750 11,250
Forward trim 1,000 <
Reverse trim 1,000 <
Motor settings:
  Motor PWM-frequency:
Low frequency uncheck <
High frequency check <
Load Control:
Reference parameter 11,300 <
Control parameter K 60 <
Control parameter I 120 <
Control influence 255 <
Special options:
  Preserve direction check <
Persistent acceleration uncheck <
Persistent speed check <
Persistent functions check <
Sound settings:
  Volume 255 127
Driving Sound Rate:
At min. speed 1,000 <
At max. speed 1,512 1,576
Random Sound:
Min. gap 30 10
Max. gap 50 <
Braking Sound Threshold: 14 <

3772 after dark:

My Märklin 3772 DB 63 212 225-7 decoder functions:
Märklin 3772 DB 212 225-7
mfx 60932 Light Drive
Horn Small
funct. dir. front rear int.LH int.RH short long low high
f0 forward on                                   
reverse   on
f1 both     on                              
f2 both       on                            
f3 both         on                          
f4 both           on                        
f5m both             on                      
f6m both               on                    
f7m both                 on                  
f8 both                   on                
f9 both                     on              
f10m both                       on            
f11m both                         on          
f12 both                           off delay off      
f13m both                               on    
f14m both                                 on  
f15m both                                   on
Stop forward                                    
Drive forward                                    
 f??m = momentary function

A screenshot from my Märklin Central Station 1:

The left part is the converted locomotive, the right part is my other 3772 with it's original c80 decoder.

The parts I have used to upgrade the Märklin 3772:
Märklin no. Pcs. Description
60924 1 mfx high performance conversion set for lfcm motor,
motor and small parts only
60932 1 mfx sound conversion set for Diesel engine
456200 1 Decoder holder
70163 2 Close coupler (from coupler set 7203, 50x 70163)
?? 2 Coupler pocket, short Preliminary
218210 2 Centring spring
345760 1? Front (bogie end) coupler pocket Future
286400 2? Rear (motor end) coupler pocket
- 2 Bulb socket cut from a SIL connector
- 2 28 Volt T1 bulb for interior light
- 2 Small experiment circuit board for wire distribution

Prototype information, from Wikipedia and others:
Road numbers: V 100 2001 - 2381
212 001 - 331
212 342 - 381
213 332 - 341
Number built: 381
Building time: 1962 to 1966
Manufacturers: Maschinenfabrik Kiel (MaK), Krupp,
Henschel, Krauss-Maffei, Jung,
Klöckner-Humboldt-Deutz (KHD)
Axel arrangement: B'B'
Total length: 12.100 mm
12.300 mm from 212 022
Height: 4.250 mm
Width: 3.115 mm
Weight: 63,0 t
Axel weight: 15,8 t
Total wheel base: 8.200 mm
Bogie wheel base: 2.000 mm
Max. speed: 100 km/h (65 in low gear)
Engine type: MB12V652TA, 12 cylinders
Engine power: 993 kW / 1.350 ps
Starting power: 177 kN
Power to weight: 15,8 kW/t
Power transmission: Hydraulic
Heating system: Steam boiler
Safety system: Sifa / Indusi

I have another Märklin 3772, in original condition.

This locomotive will probably stay in it's original condition.

Some information about the prototype:
Wikipedia about DB_Class_212
Epoche 3 - Schienenverkehr