A few pictures of my Nicci & frank mods
2 holes in the bottom to let the sound out
Inside, new weights, to replace the one removed, fitted under tender top.
55021 decoder fitted, LGB clock fitted to one axle, reeds under to operate bell & whistle. External volume control fitted under tender top.
Storage capacitors housed under coal, & acces to volume control .
The decoder is programmed with a start voltage of 5 which allows the sound to start before the loco moves. There is a decoder in the loco as well. It's a waste of time trying to reprogram the sound unit for DC, it doesn't seem to make any difference.
The sound runs perfectly & whilst I run it on DC it is fully DCC as well.
It plugs onto the four pins on the motor-block.. It will come with the instructions.
You do need to screw it to the weight, in the loco / tender. - To get rid of heat.
BOTH motors would need to be fed from the unit (I am assuming both tender and loco have motors, not so for all versions). - You may have to be 'creative' with the wiring between loco and tender? - As I say, depends on the version you have.