I have a DCC F7 A and B Unit. The A unit runs smoothly and functions over a wide range of speeds at reasonable cab settings. The B unit requires considerably higher voltage to attain the same speeds and does not run smoothly. I've tried various CV settings trying to balance the two units so I can consist them. Please help/
The Bachmann F7A and B units are identical in every way, except the shell. Assuming you have identical decoders in each loco.... I would look for something a little out of alignment with one of the locos.
I always start with the trucks:
Are the pick up brushes aligned and free of hair/fuzz? I have experienced this problem.
Are the trucks' wires securely connected from the brushes to the board? I have experienced this, too.
Even dirty wheels can prevent one from successfully programming a locomotive.
Are the F units from the same era? Is one a "plus" unit? The mechanicals are the same, but electronics are different.
Point is: you are looking for something physical that is not the same between the two units.
Regards,
Jonathan
As already mentioned, most of the time the problem lies in the fact that the wheels are dirty or the pick up brushes arent aligned or free of fuzz.