As well as being an iconic-looking locomotive the huge Alco C-855 also had an individual sound being powered by two Alco 16cyl 251C prime movers.  Together they developed 5,500 horse power and would’ve really rumbled as they passed by.  ESU have captured the right sounds and made them available for their V4.0 and new V5 LokSound decoders so in this post I’ll show you how I install sound into these locomotives.

Although the chassis has a step down section at the rear of the locomotive I wanted to add a good size speaker to ensure the sound has some bass to it.  The easiest solution is to cut a section out of the top chassis as you can see below.

Cutting the chassis just behind the inner screws leaves enough room for the speaker and provides a plastic shelf for it to sit on above the worm gear. The worm gear is below the top of the plastic so it won’t catch the speaker.  The chassis has already had parts cut out of the chassis making it lighter.  But given the sheer size of the locomotive, the fact that it pulls like a tractor anyway, and it will be running in a set of three, a little more removed will not be a problem.

The new Lokssound V5 micro sound decoder is a neat package and comes with a good 4 ohm speaker already attached and parts to assemble a speaker enclosure.  This chip came with an 8 pin plug, but as it will be hardwired in, the plug will be cut off.

Unlike the V4.0 Micro decoders which had different plugs soldered to the decoder all the V5 decoders are actually the same.  Below you can see copper pads on top of the chip.  This is actually a removable part with a Next18 socket underneath.  Next18 means it has 18 wire connections.

The chip looks like this.  The six copper solder pads next to the plug are for auxillary functions 5, 6 & 7 as well as stay alive connections.

The underside of the socket has no connections.

The flexible cable can be cut off leaving the socket section and copper solder pads.  The pads include track power positive & negative, motor positive & negative, speaker positive & negative, front & rear headlights, auxillary 1 & 2 and the common positive.

I will be mounting the decoder at the front of the locomotive behind the cab.  There are two ideal power fixing points to connect to.  Bridge wires will also need to be run to the corresponding screws at the rear of the chassis because the glue used to extend the chassis isolates the parts.  See the previous post about fitting a decoder to read more about this, which can be found here.

The original chassis came with a light bulb for the headlight which was attached to the screws via a contact plate.  But as this will need four connections, and I’ve lost the original plates, it’s easy to make some more.  For this I tend to use the excess solid core wire from a resistor, as shown below.

I wrap the wire around the screw.

Solder the ends together.

Cut off the rest of the wire and it’s ready to go.

The one screw which is sunken into the chassis, behind the one with the new contact, can’t be modified in the same way.  For this one I simply strip off enough insulation from the wire and wrap it around the screw twice.  Then as the screw is tightened down it grips the wire.  Make sure you wrap the wire clockwise so as the screw is tightened it doesn’t undo the wire.

With all the connections soldered to the pads the socket can be seated into the area behind the front screw.  But as the chassis is metal it will short out on all the solder pads, so cover the area with Kapton tape first.

The socket can then be put in place and the wires taped down.  Remember to set the wires in the middle of the chassis otherwise the shell will not seat properly.

One thing to note is the decoder will be sat directly above the screws which are delivering track power so the decoder should also be wrapped in Kapton tape, except for the Next18 plug.

The ESU speaker enclosure comes in four parts.  A base, two thin sections and one thick allowing different heights to be made.  Even with the chassis cut down one of the thin sections will need to be left out.  I use superglue to fix the enclosure together and to the speaker frame, ensuring not to get any on the actual speaker.

The assembled speaker can then be placed at the rear of the chassis with the wire connections at the top facing forwards.

The top of the speaker is just about in line with the top of the decoder which sits just under the roof line of the shell.

You may have also noticed the brown wires from the decoder socket were not quite long enough.  I could’ve replaced them but it was just as easy to extend them, covering the joint with heat shrink. If you’ve never worked with heat shrink before I did a ‘how-to’ on it which can be found here.

With the decoder plugged in the chassis is now ready for its trucks and then testing.  This particular chassis is for a C-855 B unit so I haven’t added any headlights, but both the C-855 A units will have lights, so I added wires from the socket and included a resistor which is tucked under the front of the decoder.  Below you can see all three chassis ready to be fitted to their respective shells.

The chassis have been tested and sound very good but installing the shells will add an extra level of resonance, increasing the volume. Once they are totally finished and fitted I’ll share a video with you so you can hear all six Alco 251C prime movers running.