"Motor" of the C-track-turnouts
Märklin has introduced new drives for the C-track-switches since its original release. Reason for this was the unreliable circuit of the past drives in connection with bouncing the drives or switch contacts, which in some caused damage to the decoder or its output stage.
Old & New
From the above picture one can detect the differences.
The old driver motor possessed only one micro switch, which switched power from the active coil to the passive coil via yellow cable, if the end position were achieved. Depending upon switching direction, the switch contacts sometimes spring back resulting in a floating state. At this stage there is not enough power to fully complete the switch maneuver and the drive motor would have to be set back to its previous state which was the active coil. When this happens then there is a potential of 1.3 to 1.8 A being supplied from the booster, which will either damage the coil or the power transistor. The new drive however is symmetrically structured with two micro switches, which function however only as an on-off switch. The mechanical construction does not indicate a increased resistance, even if one pushes the drive back easily, so that the switch closes again, it is pressed immediately again into the end position and the switch opens again. Smoking of the decoder and/or coils has been basically eliminated.
However the lower impedance of the coils could create problems: With the old decoder the resistance of the coils amounted to 12.5 ohms, now there is only 11.2 ohms. The end result would be an increased power input to the switch coils, shortening the switching response time and thus the length of time that current will flow through the coils. This should reduce the amount of heat generated when performing repetitive switching functions.
The use of two micro switches offers the possibility of an optional acknowledgement system which is not connected in parallel to the blue wires. Unfortunately Märklin blocked the pins with headings made to separate the switches - probably to simplify the layout. However the yellow cable is connected to the central link for the micro switch located at the top in the above picture, with the other micro switch located at the bottom in the above picture, the corresponding blue cable is attached at the central link.
If one wants to implement an acknowledgement system by using the voltage potential of the yellow cable (depending upon decoder plus or ground), then one must switch the connections of the blue and yellow cable connections of the bottom micro switch in the above picture). The two answering cables are soldered on to the free middle contacts.
This translation was made by Matthew Romer. Many thanks to him for this grateful work. Some mistakes you probably find are my work as result of trying to correct some misunderstandings.