6 Installation and Wiring
General information:
There has to be enough free space inside the engine so that the decoder can be mounted without
exerting mechanical stress. Pay particular attention that no pressure is applied to the decoder when
the loco housing is being reinstalled and the wires can’t get caught by movable parts.
All direct connections that are present in the original wiring configuration between the power pick-ups
(wheels and wipers) and the motor must be isolated; otherwise the motor end stage may get dam-
aged at power-up.
The same goes for the headlights and other additional accessories, which must be completely iso-
lated.
Do noise suppression components on a locomotive motor have
a negative effect on motor regulation?
Yes, sometimes . . .
Explanation: Motors of model railroad locomotives are often equipped with choke coils and capaci-
tors, which are supposed to suppress or filter out electric noise caused by sparks arcing across the
motor’s brushes (causing poor TV reception etc.).
Such components impair the motor regulation. Compared to others, ZIMO decoders manage quite
well and there is hardly a difference in performance with or without those components in place. How-
ever, in recent years larger choke coils are being installed in many locomotives than was the case
earlier – and these can noticeably compromise drivability.
The potentially “harmful” choke coils are often recognizable by their shape, as they look like a resistor
with color bands (in contrast to a wire wound ferrite bar). That doesn’t mean though that these choke
coils have a negative effect in all cases.
Lessons learned and accompanying measures…
ROCO, BRAWA, HORNBY – so far present no problems, no action necessary.
FLEISCHMANN H0 with “Round motors” – choke coils are no problem; capacitors should be removed
if necessary, especially the ones between frame and motor (may destroy the decoder if left in place)!
Newer Bühler motors – no problems so far.
TRIX H0 – choke coil between track and decoder plug should be removed!
MINITRIX, FLEISCHMANN PICCOLO – very inconsistent; removing of capacitors is often advanta-
geous; choke coils on the other hand presented no problems so far.
Indications of a harmful effect of such components, besides a general unsatisfactory motor control
(jerking…), are:
- weak BEMF compensation: as confirmation, set the decoder for testing purposes to low frequency –
CV #9 = 200 – and see whether the control compensation becomes stronger. If that’s the case, the
choke coils are most likely to blame.
- if a difference in compensation is noticeable between 20 kHz and 40 kHz (selectable in CV #112, Bit
5), it is very possible that the choke coils or capacitors are the cause.
Remedy: Bypass choke coils (or replace with wire strap)! Remove capacitors! Capacitors are less
likely to interfere with motor regulations.