General Maintenance and Troubleshooting
SM 6495, Rev. 7, December 2008 3-1
3. GENERAL MAINTENANCE AND TROUBLESHOOTING
WARNING
To avoid bodily injury when performing any maintenance on the Model
95 Gate Mechanism, the following steps MUST be taken:
Position the gate arm of the Mechanism being serviced in the desired position (See
Section 3.2.9),
Electrically disconnect the Mechanism being serviced by loosening the gold nut on
Terminal 5B, and
Remove and insulate the B12 (or B24) supply wire from Terminal 2C.
3.1. Safety Considerations at Multiple Gate Locations
When performing maintenance on a Model 95 Gate Mechanism with the gold nut (5B) open (Figure
3-2) and pinning the gate in the UP position, it is possible to back-feed an adjacent Model 95
Mechanism with enough energy to prevent its Hold Clear (brake) coil from de-energizing when the
crossing is activated. As a consequence, the gate arm of the adjacent mechanism may not descend
when required. This is only possible if multiple Gate Mechanisms at a given location share a common
UP Control input. This is not a problem if each mechanism has its UP Control input derived via
separate contacts of the Crossing Control Relay (XR or XPR).
Therefore, the best practice is to provide the UP Control input to each mechanism at a multiple-gate
location through a separate contact of the Crossing Control Relay (XR or XPR). If a solid-state
controller provides the Crossing Control output, this output should drive the XR, instead of using it to
control multiple mechanisms through diode-OR’d circuits.
If the above recommended best practice is not feasible for whatever reason, one of the following
actions, in addition to opening the gold nut (5B), shall be taken for the gate that is being taken out of
service and locked in the up position:
1. Place insulation between the power down contact 3A-3C (Figure 2-2, Figure 2-3, Figure 2-4, or
Figure 2-5), or
2. Disconnect the Gate Control (GC) wire at terminal 1C.
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