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Next on the upgrade list is an MTH A-B-A NKP Bluebird set.  A couple questions here if you can give me some direction.  First, I believe all 3 units are powered.  If that is the case, do I need a cruise commander in each unit?  If that is the case, I may opt to make one unit a dummy to cut the expense.  My thought is to make the trailing A unit the dummy so that I do not have to tether all the way back to it.  However, it would be nice to have the B unit as the dummy so I could use the other A unit alone. 

Thoughts and suggestions?

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The simplest install is a Cruise Commander in each engine. Not so simple is use three Cruise Ms and a single radio board. John has created a board to make that possible as it boosts serial data. You might also have to replace the tethers to ten pins for the added serial data and direction signals.

A big advantage of the latter setup is all three engines will run in synchrony, especially if you tie all the pickup rollers together with one of the tether wires.


Last edited by Norton

I did an A-B-A and built this little board to boost the serial data and the PWM outputs from the R2LC.

I'd post a picture of the actual PCB, but I only built up one to use for this upgrade.

This allowed me to put just the CC-M in the trailing A-Unit and control them both from the lead unit.  The reason I like this better than a separate Cruise Commander in the trailing A is they never get out of sync with each other, the trailing unit is getting positive control from the lead unit.

TMCC Motor Driver Buffer PCB-FrontTMCC Motor Driver Buffer PCB-RearTMCC Motor Driver Buffer Schematic

I also mapped out the 10-pin tether K-Line uses, and I found they included four grounds, which gave me the pins I needed to send +5V and the PWM signals to the trailing unit.  Crude, but I just needed it for this job.  I decided to scan it anyway as someday I may see another one of these.

K-Line A-B-A 10-pin Tether Pinouts


Images (4)
  • TMCC Motor Driver Buffer PCB-Front
  • TMCC Motor Driver Buffer PCB-Rear
  • TMCC Motor Driver Buffer Schematic
  • K-Line A-B-A 10-pin Tether Pinouts

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