# Bachmann F7 sound



## irishthump (Jul 1, 2013)

Guys,

Just got a birthday present from the kids; Bachmann F7 A+B units with sound onboard.
Running very well but noticed that acceleration and deceleration are a bit jerky and changing the relevant CV's doesn't seem to help.

Could it be a BEMF issue? I noticed on the data sheet on the Soundtraxx website it has BEMF default at 0. Does this mean it's switched off?

Thanks in advance for any help guys.


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## Brakeman Jake (Mar 8, 2009)

CV10 is BEMF Cutout so 0 means it is fully active.Your problem may indeed be from BEMF as the decoder is trying to pace the loco by compensating for differences in the effort needed to stable speed,like going uphill or downhill for instance.

I wouldn't bother for minor jerkyness with a new loco...BEMF may be trying to compensate for stiffness in the gear drives.Loco will loosen after a while and the problem may go away on its own.Right now,trying to tweak settings may have to be re-done after a few hours of running.


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## irishthump (Jul 1, 2013)

Thanks Jake,

I've given it a running in and like I said it's quite smooth. The "jerkiness" happens from as you go between speed steps. Even with a high amount of momentum it seems to jump rather them accelerating smoothly, it's hard to describe.

But as you say it's only had an hour or two's running, so we'll see how it goes.

Otherwise I'm delighted with these locos.


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## irishthump (Jul 1, 2013)

Well after doing some more online searching I have both units running much better.

I did some tweaking of CV's 209, 210 and 212 which improved things a bit. I also experimented with the Vmid setting. I didn't try this at first as it wasn't listed as an adjustable CV on the Soundtraxx data sheet!


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