I installed one of the two I received on a Digitrax SDX sound decoder in my P42 .. I simply clipped off the old capacitor, and wired the new one to the red / black wires .. locomotive runs, but I'm not quite sure if it really adds much to the running ability of the engine .. will have to clean the track first and then see what happens ..
One big advantage .. the body shell does fit back on the frame better ...
Less than 1000uF will not give you much of a "running ability". It is just to prevent the decoder's internal circuitry (and sound) from hiccups. It likely just provides several milliseconds of power. Enough to keep the decoder going during very short power interruptions.
Just to give you an idea of the size of capacitor required to actually keep the model moving for more than a second, the smallest TCS keep-alive uses a Super-Cap arrangement that totals 200,000uF. That is over 200 times larger capacitance than DCCSA.
