The Bachmann OO Class 24/25 diesel... installation guide for DCC sound...
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 simple job!
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!