MS-SOUND-decoders MS440 to MS990 Page 47
The following procedure enables the (subsequent) adjustment of driving sound to engine load (i.e. inclines,
pulling weight…), such as steam chuffs (volume and sound) with the CVs #275, #276…
Technical background:
The load-dependent sound is based on EMF (Electro Motive Force) measurements inside the decoder, which is
primarily used for keeping the motor speed constant during load changes. Before the decoder can produce the
correct sound for the respective driving conditions it has to know first what these measurements are at normal
“no-load” cruising speed (smooth rolling of the engine or train on straight and level track). This “basic load” of an
engine or train is often considerably higher on model trains than on the real railroad, which is due to gearbox
losses, power pick-ups etc. Deviations from this “basic load” will then be interpreted as inclines or declines, which
triggers appropriately modified chuff sounds.
Initiated with pseudo programming
CV #302 = 75
an automated test run is performed to record the “basic load” factor in forward direction;
By
CV #302 = 76
an automated recording run is performed in reverse direction, for locomotives that have different
“basic loads” in this direction (otherwise, the basic load in reverse is considered identical to forward).
The measured results are stored in
CVs #777 and #778
(slow/fast PWM values, forward) and
#779
and #780
(PWM values in reverse direction); these CVs can be read out and used as needed for
other vehicles, or used as base for further tests.
In case the test run is started in SERV PROG, it is important that immediately after the CV command
in CV #302 the SERV PROG is left (with ZIMO controllers the the E-key, or with the MX32/FU the E-
key is pressed twice), so the motor starts. Please do not conduct the test drive on a roller test bench,
because with higher speeds it can lead to losses of contact.
NOTE
: A “heavy” train (a train with higher rolling resistance due to power pickups of lighted coaches
for example) may have a different “basic load” than an engine with nothing on the hook. A separate
recording run may be required for such situations in order to obtain the best load dependent sound.
ATTENTION
: the engine (or train) is
driven automatically
in forward direction for which unoccupied
track must be available of
at least 5 meters (15 feet),
with absolutely no inclines or declines and
without any (tight) curves.
