The Bachmann OO Class 24/25 diesel... installation guide for DCC sound. Note that these examples are for the 21pin version
which has only 3 lighting functions (directional head/tail lights and joined cab lights). For the 2021 version, there is a
different guide, which needs a 5-function MX644C decoder instead.
First example... Not much to this installation... just remove the body shell, plug in the 21-pin MTC decoder (may need to trim
the pins a little to allow the decoder to sit a bit lower (the SL51-MTC does not have 'through' holes!), connect a 23mm round
8ohm speaker (no space for any enclosure on this one), and you're done. The speaker is not fantastic, but it is certainly a
Next example is a Class 24, which comes with a half-hearted enclosure for a speaker already, but this didn't fit any of the
better speakers, so decided to remove this provided baffle, thin the roof plastic just a little, and install a Zimo SugarLump
instead - plenty of noise and still pretty easy to do. We've also added drivers both end, and independently controlled cab
lights. The decoder used here is a Zimo MX644 21pin...
After popping off the body, we grind off the small lip in the speaker area - this will allow the Dumbo speaker to fit properly
flat in the bay. Just good enough to go in underneath the roof fan.
Add cab lights and crew both ends. The cab lights will be independently controlled.
Using FA2/AUX3 and FA3/AUX4, we solder the cab lights directly to the feet of the 21pin plug on the board. Some care required
to do this, but better than soldering direct to the decoder. Add a resistor on the +VE side for each cab light, and solder
these to the +VE pin. We've used yellow SMD LEDs in this case.
Connect up the speaker - there are pads provided on the model's circuit board for this. Tidy the wires up.
We've added a YouChoos SuperCap6800uF to the mix too - this is connected direct to pads on the deocder.
Reassemble and test!