This came up as a reply in a FB thread about using a TSU2 in a DCCready SC loco. Maybe will apply to other lighting as well, e.g. classification lights. Interesting?
Todd Wegter
Long story short: you'll have to remove the number boards wires from the motherboard and wire them in parallel with another function output. When you do that, but sure to do the math to ensure the resistor on the board is sufficient for the combined output.
Essentially, ScaleTrains uses more than 6 functions to control all the lights in their locomotives. The new Loksound 5 decoder supports up to 14 functions, 12 of which are available through the 21pin connector. In order to do this, they had to repurpose some of the pins in the NEM660 21MTC spec since it only provides for 8 functions.
The motherboard in the ScaleTrains locomotive is built using the Loksound 5's pinout so that more outputs can be used through the connector rather than having to solder directly to the decoder. This means that if you want to switch to a different decoder, any output driven by functions F0-F6 (the outputs defined in the NEM660 spec) will work if you use an NEM660 decoder. The Tsunami 2 21pin follows this spec, hence the behavior you see.
This isn't a matter of ScaleTrains doing proprietary things. Its a matter of poor (and conflicting given the differing NMRA 21pin spec) specs. Sure, you could argue that ESU has implemented as proprietary spec for the Loksound 5, but it still sticks to the NEM660 spec where necessary. So, the main crux of the problem is that you're trying to replace a 14 (12 effectively) function decoder with a 6 function decoder.
He went on to post this as well
Todd Wegter For more info about the mess that is 21MTC, see http://www.sbs4dcc.com/tutorialstipst.../21mtcconnector.html
Todd Wegter
Long story short: you'll have to remove the number boards wires from the motherboard and wire them in parallel with another function output. When you do that, but sure to do the math to ensure the resistor on the board is sufficient for the combined output.Essentially, ScaleTrains uses more than 6 functions to control all the lights in their locomotives. The new Loksound 5 decoder supports up to 14 functions, 12 of which are available through the 21pin connector. In order to do this, they had to repurpose some of the pins in the NEM660 21MTC spec since it only provides for 8 functions.
The motherboard in the ScaleTrains locomotive is built using the Loksound 5's pinout so that more outputs can be used through the connector rather than having to solder directly to the decoder. This means that if you want to switch to a different decoder, any output driven by functions F0-F6 (the outputs defined in the NEM660 spec) will work if you use an NEM660 decoder. The Tsunami 2 21pin follows this spec, hence the behavior you see.
This isn't a matter of ScaleTrains doing proprietary things. Its a matter of poor (and conflicting given the differing NMRA 21pin spec) specs. Sure, you could argue that ESU has implemented as proprietary spec for the Loksound 5, but it still sticks to the NEM660 spec where necessary. So, the main crux of the problem is that you're trying to replace a 14 (12 effectively) function decoder with a 6 function decoder.
He went on to post this as well
Todd Wegter
For more info about the mess that is 21MTC, see http://www.sbs4dcc.com/tutorialstipst.../21mtcconnector.html