If you definitely had smoke come out of tender, the RS board had to have some damage. Did you test the damaged board in your good engine? Just to ensure it was bad.
Regardless, you know the replacement board works with your old chips, so now why not work in the engine. It very well can be the LCRU. The RS May sense command mode and stay quiet, but not have serial data getting to the RS board to operate it.
So, swap LCRU from the engine. If it works the LCRU is in fact bad. If not, there must be a tether issue oif some sort. G
