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What does "basic OS loader invalid checksum" displayed on a Unity Quantum 140CPU6XXXX indicate?

This error can be seen if there was an interruption to the Executive Flash process. Sometimes the PLC is recoverable and sometimes it is not. To recover, some of the actions listed below can be attempted. Remove any PC cards installed in the PLC and any cards other than the PLC and PS from the back plane. If available, try a different power supply and back plane.

  • Power cycle.
  • Power off, press and hold the ESC key through power up.
  • Press the Restart button next to the battery.
  • Use the OS Loader to connect to the PLC using either Modbus or MB+, set to address 1 and attempt to flash firmware.
  • Power off, remove battery, remove from back plane, let sit 120 minutes and power on.

If after the above actions the PLC does not recover, it must be returned for repair/ exchange.



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