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How The PSX Senses a Short

How The PSX Senses a Short

Posted by on Apr 2, 2015 in Tips DCC Components, Tony's Tips |

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“I have 8 power sub-districts, 7 of which have the PSX-1, and one with a PSX-AR. 

Everything works fine for running a train, but when I test their ability to react to a short, they don’t. The system is powered by an NCE SB5 booster/command station, with a 12 volt, 5 amp power supply. The whole system starts blinking, including the booster.  The power busses are all 14 gauge stranded, with track feeders of mostly 20 and 22 gauge, with some 18 gauge.  The busses have various lengths, ranging from about 12 feet to about 40 feet.  Again, engines operate seemingly normally throughout. 

I’ve tried all kinds of testing tricks, disconnecting various sub-districts, to see if there would be any change in the behavior.  No success.
I need help.  Any ideas of what my problem might be?”   Joe Z

Larry Maier, DCC Guru extraordinaire and designer of the PSX offers some insight below.

The PSX only breaks one side of the circuit. J1-4 to J2-2 is switches on/off. J1-3 to J2-1 is a piece of copper. If you have wired things such that copper traces from different PSXs are in BOTH sides of the circuit, you can have a short that will not be detected by the PSX and will shut down the booster. I would disconnect the output wires from all but one PSX. Short that district and verify that the single PSX works correctly. Now add the next district and short it. If it doesn’t detect the short, flip the two input wires and the two output wires. This PSX should now work. Continue until all are working.