Inc Sound Module Decoder - Manual

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3.9 Electrically Isolating the Motor

Failure to isolate the motor will damage your decoder. For DC permanent

magnet powered locomotives, the decoder must be electrically inserted between

the track power pickups and the 2 motor brushes.

The most important part of any successful locomotive conversion is proper

electrical isolation of the 2 motor brush connections, so that they are driv-

en only by the decoder.

Once the motor is isolated, visually inspect the brushes again, just to be sure.

Use a continuity checker (beeper box) to be sure there is an OPEN circuit (very

high resistance) from both brushes to any other part of the locomotive chas-

sis, power pickups and wheels. Check both motor brushes. If the circuit is not

open, your beeper box will beep.

Only when you are satisfied that the motor is isolated, should you proceed

with the decoder installation.

Some motor brush power connections may be tricky, like a spring to or inter-

ference fit with part of the chassis. Some locos pick up brush power from the

chassis through a spring. In this case, after removing the spring connection to

the brush, wire the corresponding decoder power input to the chassis. Examine

the loco carefully to determine how power moves from the track pickups to the

motor.

Decoders with FX

functions have motor isolation protection. If the decoder

senses that the motor is not isolated, it will not run the motor. In this case, you

will be able to control the loco’s functions but the motor will not work.

For board replacement decoders, it is important to follow the Decoder

Instruction Sheet for the particular decoder when installing insulating tape

inside the loco to prevent shorts during operation caused by the decoder board

shifting inside the engine.