INSTRUCTION MANUAL

Page 56
Decoder MX620 - MX622, MX630 - MX632 Sound Decoder MX640 - MX648
7 MX631C, MX632C, MX640C, MX642C for C-Sinus (Softdrive)
The MX631C, MX632C, MX640C and MX642C are made especially for Märklin and Trix engines
with C-Sinus motors and are equipped with a 21-pin interface. The decoder also supplies the necessary
5V the C-Sinus board needs to operate (which „normal“ decoders are not capable of!).
The C-type decoder can be used, regardless of the type of motor, for Märklin, Trix and Märklin
compatible engines which cannot process normal functions on function output FO3 and FO4, but
require logic level outputs instead.
The C-type decoders differ from the normal 21-pin plug (MX631D, MX632D, MX640D, MX642D) in
the use of output pins FO3 and FO4. The D version has normal (amplified) outputs on these pins
while the C version has logic level outputs. These logic level outputs supply the needed 5V for activating
the C-Sinus or Softdrive loco board or for the selection between the front to rear power pickup,
which is installed in many vehicles.
The MX631C, MX632C (or MX640C, MX642C sound decoder) is plugged into the pins of the loco
board with the top side of the decoder pointing up, whereby the pins are being pushed through the
decoder board in order to make contact with the decoder socket. The position is given by the loco
board and is also keyed by the missing pin 11 (on the loco board) and missing hole in the same location
on the decoder board.
The picture below shows a sample layout; the loco board may however vary from case to case.
CAUTION:
Unfortunately, Märklin/Trix has played a “dirty trick” (although probably not on purpose): Beginning
with a specific model or past a certain date, the protective resistors on the loco board input side have
been omitted, or more precisely, instead of the 100kO resistors useless 0 Ohm resistors are being
installed. The resulting voltage is too high for the loco board which will not only destroy the board but
can also damage the decoder, unless the decoder has been switched to the C-Sinus mode before
being plugged in with CV #145 = 10 or 12.
But even if CV #145 = 10 or 12 is set first, there is no guarantee that the loco board with 0
Ohm resistors will survive in the long run (even though there is no visible problem at the
moment)!
Background information: Although the 21-pin interface in Märklin and Trix locomotives is virtually
identical to the standardized NMRA-DCC 21-pin interface, Märklin keeps modifying it whenever the
need arises (several versions, “misapplication” of function outputs for motor activation and now the
mentioned electrical input changes); their own brand decoder is the only one that is being taken into
account through all this. The installation of other brand decoders is obviously not desired…
CORRECTIVE MEASURE: The MX631C, MX632C or MX640C, MX642C must not be installed if
zero-ohm resistors (markings “000”) are found on the loco board in place of actual protective resistors
(markings “104”). It is imperative that these are being replaced with 100KO resistors (“104”)
before installing the decoder. Relevant ZIMO decoders will be shipped with the necessary resistors.
Loco board with 21-pin plug and MX632C plugged in
Flat ribbon cable to C-Sinus motor
Before plugging in the decoder, check the C-Sinus board whether it contains 0-Ohm resistors; see
CAUTION on the next page!!
MX631C, 632C and MX640C, MX642C are “normal” decoders for “normal” motors except for the
function outputs FO3 and FO4, which can be switched to C-Sinus motor control by programming:
CV #145 = 10 if the engine originally came with a Märklin/Trix decoder or CV #145 = 12 if the original
decoder was from ESU (recognizable by a blue circuit board).
With the help of CV #145 the decoder can also be configured for some special versions, which becomes
necessary due to different decoder interface layouts on the part of Märklin/Trix, see CV table!
Locomotives equipped with C-Sinus capable ZIMO decoders can be operated in the NMRA-DCCdata
format as well as the MOTOROLA protocol, but not in analog mode (DC)!
No motor regulation, known as BEMF, takes place when the decoder operates in the C-Sinus mode,
since the motor tries to keep the target speed precisely in all situations. The relevant configuration
variables, among them CV #9, #56 and #58, are without effect!
Above is a picture showing a loco board with the useless (“000”) resistors; in such cases it is not allowed
to plug in a MX631C, MX632C… decoder!
Due to the many different C-Sinus boards that have been produced it is impossible for us to provide
precise information about the location of these resistors on each board. Because the resistors may
be mounted in different locations on the board in your engine, we would suggest that you find them
by following the traces. First study the picture below. The blue and pink arrows are pointing out the
traces that connect these resistors with the processor. Note the processor pins those tracers are
leading to.