Updated 26.02.2011

Märklin 2848, CCB 215

Conversion parts:
For the 2848 a motor from the conversion kits 60901, 60921 or 60760 may be used, as these motors are identical.

Decoder:
The decoder, in this case a "mini 60902", Märklin spare part number 603462, is installed at the same place as the original reversing.  It is installed in the holder 456200.  The decoder comes from another locomotive, that was converted with a "more sophisticated" decoder with extra functions.  The mini 60902 has only function f0, which is front lights that change with the driving direction.

Maybe I later on will install another decoder (from the 60760 kit or an mfx decoder) in this locomotive, to give it interior light as my other V36/236 locomotives.  With the 60760 decoder and the mfx decoder also the top speed will be adjustable down to the prototypical correct speed of 60 km/h.  This low speed is not possible with the 60902 decoder.  The speed adjustment range is not wide enough.

The decoder in CCB 215:

Motor:
Installation of the motor itself is not very difficult, but requires some mechanical work in the locomotives with two light bulbs.  After removing all the existing parts (motors, delta decoder, bulbs etc.), clean the chassis and make sure that everything (transmission and wheels etc.) is turning smoothly.
Before installing the new motor:
The top of the motor cover (brush holder) is a little bit lower than the top of the magnetic field part of the motor.  In the V36 locomotives with two light bulbs in the centre, the light guide leading to the rear lamps will hit the magnetic field part, as the magnet is wider than the similar part for the old motor. The four metal plates making this width difference must be filed or grinded down to the same height as the motor cover to give space for the rear light guide.  It is best to remove the field top from the magnet.  It is difficult to get rid of all the filing dust sticking to the strong magnet.  Leave the magnet on the lower part of the magnetic field, to make sure it is installed the correct way.  If installed the wrong way the motor will rotate the wrong way.  If so, the blue and green wires to the brushes must be swapped.

Hold the magnetic field metal plates tight together with a vice or pliers when working on them.  Otherwise small metal particles may be forced down between the metal plates, making the part too thick.  Be careful with the guide pins.  Be sure that all filing dust is removed.  I normally rinse the part with hot water and dry it carefully.
The modification can be seen in the below photo.

Install the new motor to the locomotive, firstly without the brushes. Check once more that everything revolves freely. Install the brushes.

The motor in CCB 215 (the photo is the 28502.  2848 is identical except for the bulbs on top of the motor and the relay in the front):

The original lamp holders in the locomotives are used, with 610080 bulbs.

Wire connections:

Wire colour	function	Connecting to
Red wire	B (centre contacts)	pick-up shoe connector
Brown wire	0 (tracks)	locomotive ground
Blue wire	Motor brush	rear brush holder
Green wire	Motor brush	front brush holder
Orange wire	Common +	bulbs (front lamps)
Grey wire	Forward lights	front lamp, left (decoder side) lamp holder
Yellow wire	Reverse light	rear lamp, right (motor side) lamp holder

Future improvements:
Install the decoder from a Märklin 60760 conversion set and LED lights, as in my 3145. This way I may adjust the top speed down to the prototypical 60 km/h and have an extra function for interior light.
The 60760 decoder has 14 speed steps.  I think that is more than enough for the relatively low top speed.