I have a Spectrum Modern 4-4-0 (bright blue box, "DCC Sound On Board"). Can I get a wiring diagram, or a list of the 6 coloured wires and what they do?
Also, various reviews mention that this model has a cam for synchronising the exhaust chuffs. I've tried CV112=128 (Bit 7 on) and the default zero. Neither seems to have any effect. Does this loco actually have a cam? How do I activate it?
No cam that I know and I have three of those engines.
I believe CV 116 controls the chuff rate in those decoders manufactured by Soundtraxx. There are instructions in the online Soundtraxx manual for how to synchronize the chuff to be prototypical.
The chuffs will never be a prototypical even four per driver revolution. I set mine by running the engine at a good switching speed, which for me is about step eight out of 128. While you have the engine on a good piece of straight track, try different values of CV 116 until you get to even four chuffs per driver revolution. At speeds above and below it will be less accurate. Above that the engine is going fast enough that you can't really count anyway.
I've never understood those "automatic" sounds unless they are to
Provide random sounds on continuously operating public display layouts where no one is actually present running the layout.
Trainman203: I don't use automatic sounds, either. Perhaps if you're operating in DC and there's no other way to control them.
Brian: Thanks for this. The 4-4-0 isn't exactly like this, but it may help to figure things out.
This should be the reference for my loco:
https://soundtraxx.com/content/Reference/Factory-Installed/Bachmann/Spectrum/ho_modern4-4-0.pdf