# Issue between turnout servos and locos



## videobruce (Jun 15, 2011)

I did come across this thread that seems to describe what I'm getting;




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Problem with Chattering and Oscillating Servo Point Motors - Model Train Help Blog


He is a question posted by Barrie: “I have a problem with the servo motors that control the turnouts on our N scale club layout chattering or oscillating when an old type DC loco is run on the layout. This doesn’t happen if new type locos are run or the system is run as DCC […]



blog.model-train-help.com





But, other than possibly adding a 'cap' across the motor leads (1mf ceramic disc I would think), that was the supposed 'fix'. Anyone else heard of this happening??

Again, it's just 5 out of 30 locomotives that are causing the problem. All Atlas; GP20, GP40, GP7. Funny thing a *3rd* GP40 doesn't cause the problem.

BTW, all those units run smooth & quiet by themselves, no stalling, sputtering or finger needed to get them to move. 

Your thoughts please.


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## gregc (Apr 25, 2015)

suggestting it's RFI, radio frequency interference, sonuds like voodo and mysticism.

if the servos are powered by track power, then maybe the older engines are causing track power to fluctuate or possibly noise on the servo control pulse. isolating the servo and track power may help, but is a good idea, regardless


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## videobruce (Jun 15, 2011)

Servos are powered thru a Servo Controller from a 5vdc 30 amp PS.
There are certain areas that seem to be affected more than others. The closest servos to the loco are the ones affected. I have over 60, only a few chatter at one time.


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## Lemonhawk (Sep 24, 2013)

If its RFI then maybe 0.01 or 0.001 uf. I find this a little hard to believe that its RFI. Are you running the servo cables right next to the DCC cables? Have you tried twisting the servo cable? Or the DCC cable?


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## SF Gal (11 mo ago)

Feedback through the shared transformer power supply is my guess. I bet if you switchover all the accessories to thier own dedicated transformer, you will isolate the feedback on the line and eliminate the problem.


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## videobruce (Jun 15, 2011)

1. DC operation, 3 cabs, all transistor throttles,
2. Dedicated PS's for all, separate 5vdc 30a supply,
3. Servo cables are flat leads. Power feeds are separated from the servo leads for the most past by a foot or more.

This can't be anything other than RFI, the Atlas GP40's are the worst, they chatter servos (not all at once) across the entire layout (9x19 foot room).


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