# Motor capacitor



## Patrick1544 (Apr 27, 2013)

Hi
I am inquiring about a photo of a motor with a capacitor across the brush terminals. What is the advantage of doing this? Should all motors have one or just older Lionel Post-war Pullmoor Motors? Whats the Cap value to use? Are they dependent upon the Motor's amperage draw?


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## gunrunnerjohn (Nov 10, 2010)

The capacitor is to suppress noise from the brushes. Typically, on a Lionel AC motor that has TMCC, the value is 1uf non-polarized. What you have there is a .22uf cap, but it serves the same function.

You can use them on DC motors as well, however note that some cruise control may be affected by a shunt capacitor, the back-EMF cruise of the ERR products comes to mine.


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## Mark R. (Jan 26, 2013)

They are there to suppress the RF (radio frequency) emissions created by the brushes sparking. This wide band interference can affect the signal of other devices in the general area. 

I remember as a kid, my slot car set would cover the TV screen in random lines - that was back in the old black and white analogue days ! 

Mark.


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## Mark R. (Jan 26, 2013)

That's true John - those caps should be snipped off if you are using any decoder that provides BEMF functionality as it will interfere with it.

Those caps really aren't that important any more with the progress of digital signals now for TV, radio and phone. They are still a requirement in many European countries though - that's why you will still see them in Bachmann products as Bachmann has a huge European market base.

Mark.


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## Patrick1544 (Apr 27, 2013)

Thanks for the info. Wasn't sure if it was a running improvement or a filtering device. Now I know!


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## gunrunnerjohn (Nov 10, 2010)

Sometimes it improves the running of other things like radios and TV's.


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