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ErrorLib — Industrial Fault Code Library

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SV0381

ABNORMAL PHASE (EXT)

Fanuc · Alpha i Series Servo Amplifier

What does SV0381 mean?

An abnormal alarm in the position data occurred on the separate linear scale. This indicates an issue with the phase signal generation or detection from the external linear scale.

Common Causes

  • Signal degradation or noise affecting the phase signals of the external linear scale.
  • Physical damage or contamination on the external scale's reading head.
  • Malfunction in the external scale's signal generation circuitry.
  • Incorrect installation of the external scale, causing phase shift.
  • Encoder signal processing fault within the servo drive.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Clean the external scale's reading head and scale surface.

  2. 2

    Measure phase signal levels from the external scale's output terminals.

  3. 3

    Verify correct installation and alignment of the external scale.

  4. 4

    Check servo parameter P1-04 (External Encoder Type) for correct selection.

  5. 5

    Inspect external scale for any visible damage to the track or head.

Browse all codes in this manual (101)
Verified technical data. Last updated: April 2026

Related Faults

0233Velocity Pulse Count Exceeded0243Position Pulse Count Exceeded0434Velocity Loop Integral Gain Overflow
Source: Fanuc Alpha i Series Servo Amplifier
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