Wednesday, November 01, 2006

OERM Signal Activities - Oct 28-29

Mapes Crossing Rebuild Activities ----
1.) Adjust track circuit (both North-old and South-new Safetran). On new Safetran audio track circuit, trying to get reliable operation at approx 10 feet past track wires with minimal overring beyond that but had trouble limiting overring while still get full track circuit (between track wires) operation.
2.) Replaced track relays with 900 ohm units (mistakenly replaced with 62 ohm units earlier).
3.) After track relay replacement and circuit adjustment, test of the crossing showed unexpected (phantom) operation of the lights/gates every 30 seconds.
4.) Troubleshooting of 3.) showed both NTR and STR (north and south circuit track relays) did not drop, but at time of activation, the XSR (crossing stick relay) dropped. Measuring the voltages in the relay contacts feeding the XR (crossing relay), it was determined that a contact in the NTR was bad and held shunted by the stick circuit so that when the stick circuit timed out at 30 seconds the crossing would restart. Replacing NTR solved the problem.
5.) Auxiliary Flashers/bell for southbound 'A' street was connected at both the flasher end and the 'A' case end.
6.) Crossing was tested.
7.) Open issue -- overring on South Circuit is larger than desired -- Gene will be contacting Safetran Applications Engineers to determine plan of action. The circuit is fully operational as is -- island is slightly larger on north side and south approach is longer than before.

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