# How do I add a Keep Alive to a sound only decoder?



## tkruger (Jan 18, 2009)

I have a project that is using a sound only 0001908 sounder decoder by MRC. This is in a steam powered rotary plow. I want to add a current keeper so that the sound does not skip on the frogs. How do I add this? All of the ready made ones I see have a white and a blue wire. Do I just replace the capacitor that is currently on the sounder with the keep alive unit? Can I just replace the capacitor that is there with a bigger one? What is the best option?

Little history on this project. Built the rotary from an Athearn Blue box kit, used a Riverossi tender, converted the tender to use Kaydee couplers. Connected the plow with a draw bar to the tender, powered the plow blade with a motor from an broken toy, using an NCE motor decoder set the blade to spin at a constant speed regardless of the set throttle, added two forward led headlights and finally added the MRC steam sounder. Currently I have about $50 dollars into this project counting everything. My goal was to make a budget plow that had everything. 

The decoder being used for sound:









The project in its current state:


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## Lemonhawk (Sep 24, 2013)

The capacitor is probably a coupling cap to the speaker to prevent DC from getting to it. Some how you need to figure out where on that little board it converts the track voltage to DC and put a proper stay alive cap and resistor/zener at that point.


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## wvgca (Jan 21, 2013)

To increase DC reserve capacity on the sound only board, it's just a matter of replacing the existing capacitor with a larger value one, keeping the same voltage rating [probably 25V] ..
As a guess from the size of the cap in the image, it may quite likely be less than 100uf .. and a new one around 470uf should work, as it's sound only with no motor drive,if you have the physical room ..


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