Looking for a diagnosis of a problem with a legacy Big Boy. Running a lashup with 2006 Big Boy on front and 2010 GE hybrid behind. Ran well for a time, then stopped. Hybrid still works, but Big Boy drawing lots of amps (~8) and not responding. Lights function, but won't move with controller command. Sound like an RC board or motor driver board failure, or another motor problem?
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First off, how about an actual Lionel product number? Is this the Vision Line, the more recent BB, or the first 2006 Legacy version? It makes a big difference in the advice we give.
It’s the original 2006 Legacy Big Boy. It had run well in a lash up previously. Just stopped suddenly this time.
That's the information we need. 
JLC Lionel Legacy Scale Big Boy Parts
Since this locomotive has the excellent Pittman motor, my top suspect is either you have something jamming the drive or the DCDS may have cooked one or more of it's FET's.
If you take the shell off, you can rotate the motor through a full rev of the drivers and see if there's any binding. If not, my next step would be to unplug the motor from the DCDS (black connector), and suspend the locomotive so the drive wheels are free. Using a DC supply around 6V, test the motor and make sure it runs in both directions while driving the drive train. Measuring the current of the motor is a big plus here, we're trying to determine if it's healthy.
If both of those tests are successful, it's most likely the DCDS. If it's the FET's or the bridge, they can normally be repaired. If it's something else, it's likely replacement time.
Thanks for the ideas, John. Things to try.
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