ZIMO MX638 Series Instruction Manual page 62

Page 62 Non-Sound Decoder MX618 - MX638 and Sound Decoder MX640 - MX659
MX631C, MX632C, MX634C, MX642C MX644C... for C-Sinus (Softdrive)
The MX631C, MX632C, MX634C, MX640C, MX642C and MX644C (C-type) decoders are made es-
pecially for Märklin and Trix engines that are equipped with a C-Sinus motors and come with a 21-
pin interface. The decoder also supplies the necessary 5V for the C-Sinus board (which "normal" de-
coders can't !).
These C-type decoders can also be used for Märklin, Trix and Märklin compatible engines that
come with other types of motors but cannot process normal outputs on function output FO3 and FO4,
but require logic level outputs instead.
The C-type decoders differ from the normal 21-pin plug decoders (MX631D, MX632D, MX634D,
MX640D, MX642D, MX644D) in the use of output pins FO3 and FO4. The D-type has normal (ampli-
fied) outputs on these pins while the C-type has logic level outputs. These logic level outputs supply
the needed 5V for activating the C-Sinus or Softdrive loco board or for the power pick-up switch found
in many vehicles.
The MX631C, MX632C, MX634C (or MX640C, MX642C, MX644C 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 prevents a wrong installation by the missing pin 11 (on the loco board) and miss-
ing 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.
L o c o b o a rd w ith 2 1 -p in p lu g a n d M X 6 3 2 C p lu g g e d in
Before plugging in the decoder, check the C-Sinus board whether it contains 0-Ohm resistors; see
CAUTION on the next page!!
All C-type decoders are "normal" decoders for "normal" motors except for the function outputs FO3
and FO4. They can be switched to C-Sinus motor control by programming CV #145: specifically,
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). Depending on the C-Sinus motor de-
sign a setting of = 11 or = 13 may deliver a better result (try it!).
With the help of CV #145 the decoder can also be configured for some special versions, which be-
comes 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-DCC-
data format as well as the MOTOROLA protocol, but not in analog mode (DC)!
No motor regulation, known as BEMF, is possible 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 such as CV #9, #56 and #58 have no effect!
F la t rib b o n c a b le to C -S in u s m o to r
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 have been omit-
ted, 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 with CV #145 = 10
or 12, before being plugged in.
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 if there is no obvious 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: C-type decoders 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 imper-
ative that these are being replaced with 100KO resistors ("104") before installing the decoder.
Above is a picture showing a loco board with the useless ("000") resistors; in such cases it is not al-
lowed 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 trac-
es that connect these resistors with the processor. Note the processor pins those tracers are leading
to.