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ErrorLib — Industrial Fault Code Library

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SRVO-251

Servo Amplifier Internal DB Relay Abnormal

Fanuc · R-30iB Mate + Mate Plus Robot

What does SRVO-251 mean?

An abnormality has been detected in the internal DB (Dynamic Braking) relay of the servo amplifier. This indicates a fault within the amplifier's internal circuitry responsible for dynamic braking.

Common Causes

  • Internal dynamic braking (DB) relay in the servo amplifier has malfunctioned.
  • Overheating of the servo amplifier causing DB relay protection to activate.
  • Short circuit within the servo amplifier's braking resistor circuit.
  • Power surge or voltage anomaly stressing the DB relay.
  • Mechanical failure of the DB relay contacts.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Replace the servo amplifier.

  2. 2

    Replace the E-stop unit.

Browse all codes in this manual (53)
Verified technical data. Last updated: April 2026

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Source: Fanuc R-30iB Mate + Mate Plus Robot
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