 PSS test conducted twice a year to verify operation of
PSS enables and operation
 ARC1 Fails PSS certification. Will not turn off when
PSS signal is disabled
 Power Supply computer indicates that off signal has
been sent, but hardwired signal indicates that Main
Contactor is not de-energized. PSS will not drop to
OFF/Safe status
 Main contactor disables after a while, and problem is
not easily repeatable.
 Main Contactor is sticking and does not decouple
when control voltage is disabled.
 Investigation finds that Auxiliary contacts have been
attached onto Main contactor using screws that were
too long
 Long screws break through Bakelite material and
small pieces onto rails of the armature assembly of the
Main Contactor. This may have contributed to some of
the “stickiness”, but not conclusive.
 ALL power supplies with Auxiliary contacts have been
checked for correct screw lengths.
 9 Additional Supplies found to have incorrect screw
length and minute debris in the Main Contactor
 All Contactors cleaned, voltage tested and replaced
 Additionally, power supply schematics are being
revised for quicker diagnostics in the future
 Changes or additions to existing equipment must be
fully analyzed for correct configuration
 Non-routine tasks must be evaluated before work is
conducted
 Test all equipment before installing
 Update schematics