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Bachmann OO N Class DCC Sound

Example 1: MX648, firebox LED, front lamps, speaker in tender

The Bachmann OO N Class... detailed installation guide for DCC sound...!

Here we are fitting a Zimo MX648 sound decoder in the loco, with a plan to trail 2 wires back to the tender for the speaker. There is no room in the loco itself for a speaker. So, with the loco's body removed, remove the DCC socket, trim down the socket's screw mounts and neatly attach the MX648 in its place. We've used some thin electrical tape to secure it in place. Neatly join the red and black decoder wires to the pickup wires, and solder the decoder's orange and grey wires to the motor terminals (test after doing this that movement is in the right direction, and swap around if necessary):

While we're at it, a firebox glow light is added (orange SMD, carefully drilled into a ground-out hollow), and we'll make provision for a couple of YouChoos working loco lamps, creating shallow channels along the centre base of the chassis for the wires to sit in:

The lamps have 'live' legs, and the N Class chassis is metal, so the lamp holes are oversized so that we can also insert heat-shrink protection to avoid shorting the lamps. Once done, carefully super-glue the lamps (minimal glue to avoid sticking up the sprung buffers!) and their wires into place and along the channels made earlier. We'll add a single resistor per lamp to the +ve wires of the lamps inside the body:

Sorry, I forgot to take pictures beyond this point (!), but it is then relatively straight forward to join each LED's +ve to a resistor, then together to the decoder's common +ve BLUE wire. The decoder's WHITE and YELLOW wires connect to the -ve sides of the loco lamps, and the decoder's GREEN wire is configured for the firebox glow's -ve.

Thread the 2 PURPLE speaker wires through, perhaps via the round hold in the centre at the back for neatness, and refit the loco's body. The tender will need to be dismantled, but there is plenty of space for a decent speaker back there, such as a Zimo 39x20x9mm rectangular bass reflex.

Example 2: MX648 with 40x20 1W speaker in tender

Here is another example, with some more detail on the speaker installation...

Remove loco body and remove the existing 6pin decoder. Also remove the DCC socket circuit board, and all additional components to the motor:

Install the Zimo MX648 decoder, taping it to the motor tower. Orange and grey to the motor terminals. Red and black to the pickups. Keep the wires short and neat, as there won't be much room for the wiring to go when it all gets reassembled again later!

I'm adding a firebox glow light to this model too, which takes some time to drill through because the metal is very thick! Start with a small drill, then enlarge the hole.

The firebox light will be connected to the common positive (blue) of the decoder, via a resistor (very important to include the resistor, or the LED will instantly go POP!), and also to the green function output (negative of the LED). The LED itself is a flat super-bright orange SMD, glued to the back of hole we drilled, and some electrical tape over the top for extra protection, and to encourage the wires to go UP rather than wave around madly!

Carefully encourage the wires to go where you want them, without pinching anywhere, and reassemble the body and chassis. Note the purple speaker wires trailing through, which will soon be connected to a speaker in the tender. Test that you get correct motion (swap orange and grey around if it runs the wrong way), and test that the firebox glow light functions correctly.

Now for the tender... In this example I want to use a 40x20x10mm box speaker, which means cutting out part of the coal moulding. This is done with a combiation of Dremel and files. I've then used some thin card, tape and blu-tac to reshape the coal moulding, painting it black on the top, and stuck on some Woodland Scenics coal ballast (lump coal), which looks nicer than the original moulding anyway!

NB we'd suggest using an IceCube25X18X08-1W speaker instead now.

I decided to change where the speaker wires come out from the loco, to use the circular hole, which is neater, and added some weathered crew figures at the same time:

Wiring up the speaker is very simple:

Reassemble, ensuring that the speaker wires are tucked in neatly, test, and we're done!


Please note that these guides are provided as useful resources for you, as-is. YouChoos cannot be held responsible for errors in the information, or for any damage caused to your models or equipment if you choose to follow any of the steps detailed here.

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