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2.5 BB BUS FET Short

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Written by Ollie Wells

Symptoms:

  • BUS_FET_SHORT Fault on the DCDC is the first fault — can be followed by FLY_CAP (both under voltage and over voltage).

  • It is important to go back in Grafana to check which was the first domino to fall.

What is the failure behind the fault?

  • There is a FET on the BUS side which can get shorted. The detection/fault is based on inrush of current from the DC BUS side when the DCDC is trying to go Active and pulling the DC BUS up.

Troubleshooting Steps:

  • On SYSGUI use the Reset Processor button. Do this three times. If that does not work, continue to the following steps.

  • Bring System to Standby.

  • Wait 10 seconds.

  • Bring System to Active again.

  • If not solved (remote CAN needed):

    • Bring System to Standby.

    • Enumerate the block misbehaving to CAN ID 0 — this will make sure it is the first block to go Active.

    • Bring System to Active.

    • If it fails, retry for a total of 3 times.

    • If the failure persists: Call out RMA.

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