Loco runs rough between speed steps 27 - 34

[philsandy]

I'm not sure if this is a DCC related problem, but I have a Bachmann 4MT tank fitted with a Zimo MX 648.  

It runs very smooth at slow speeds, which is what I use mostly.

However I have noticed once I increase speed above step 26 of 128 it starts to run slightly jerky.

At first I thought this may be a mechanical problem, but increase the speed above 34 and it runs fine again.

 

Can anyone suggest a cause?

[smokebox]

Are there any capacitors connected to the motor? If so, try removing them.

[shibushe]

Yes capacitors can often cause erratic running, not always though. I have several Locos that have them in with no running problems at all.

So, yes take them out.

One other thing you can do is reset the decoder to default 3.  This often can cure strange happenings.

Its my experience to never trust a decoder even if its new, I always do a reset before programming.

[10000]

Try turning off BEMF. I've seen that do wonders with the running of small Bachmann locos

[Crosland]

Try turning off BEMF. I've seen that do wonders with the running of small Bachmann locos

Alternately, as its a Zimo decoder, read the section in the very good manual about tuning, but remove any capacitors first as these can affect the Back EMF.

[philsandy]

Thanks for all your replies.

 

I was mistaken the decoder is a Loksound V4 micro (the Zimo is in my other 4MT), anyway

I have managed to improve the running.

I snipped the capacitors but that had no effect.

I gradually increased CV55 value from 20 to 42, and now it runs smooth on all speed steps.

[Mick Bonwick]

Thanks for all your replies.

 

I was mistaken the decoder is a Loksound V4 micro (the Zimo is in my other 4MT), anyway

I have managed to improve the running.

I snipped the capacitors but that had no effect.

I gradually increased CV55 value from 20 to 42, and now it runs smooth on all speed steps.

 

A good result, and thanks for providing your findings. Others will have learned from your experience.