erratic F7 B Unit movement

[richardm]

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/

[jonathan]

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

[little railway]

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.