Re: Keep Alive Install


HI Bob,

  I don't have any factory installed decoders, so I cannot help with specifics.  However, I can give you information about the electronics, universal to all decoders.

  The existing external (wired) capacitor is actually only designed to combat light flickering.   It does not affect the motor or sound sections of the decoder.   As such, replacing it with a high value capacitor (Keep Alive) would only keep the lights alive for a long period of time.

  What you need to do is find the bridge rectifier portion of the decoder.   A bridge rectifier is made up of four rectangular diodes (black with a white stripe on one end - connected directly on the power input).  Diodes pass current in only one direction.  The diodes are connected in such a way that the incoming track current (Alternating Current or AC) is rectified into Direct Current (DC  = + voltage or Ground).   The output is polarized (approx. +12 and GND) and that is where the blue (+12 Volt) and Black w/white striped (GND) wires of the Keep Alive are connected.

  Here's a great link for explaining more:


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