IndustrialDriveDataDrive Board & Diagnostic Database
Emerson fault record

POFF: Input Undervoltage / Drive-Board Supply Indication

The keypad displays POFF immediately after power-up or only when the motor is commanded to run.

Meaning of the indication

A POFF indication may be associated with an undervoltage condition or with an abnormal drive-board sensing/supply path. A run-only POFF observation can point toward a different stress condition than a power-up POFF observation.

Checking order

  1. Separate power-up POFF from load/run-command POFF before replacing parts.
  2. Inspect the drive-board voltage-detection path and local electrolytic capacitors.
  3. Where the fault appears only under motor operation, include the drive-board transformer path in the investigation.

Suspect areas

Voltage-detection pathElectrolytic capacitorsRibbon connectionDrive-board transformer path
Fault-specific caution

Do not repeatedly restart a drive reporting supply abnormalities until DC-bus and power-stage conditions have been assessed.

Diagnostic workflow

Workflow
Emerson TD900 POFF Display Investigation

POFF is displayed at power-up or appears only after a run command.

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Evidence intake

Turn this record into a qualified service request

A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.

  • Complete drive type code / MLFB or nameplate model
  • Fault code, fault value and first event before reset
  • When the event appears: power-up, enable, ramp, run, decel or stop
  • Motor/cable connected or isolated during the symptom
  • Visible board, option-card, module and connector identifiers
  • Previous repair history, replacement parts and repeat-failure pattern
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