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FANUC Alarm LECO-051 — Cap B under voltage (Cap A volts, Cap B volts)

FANUC LECO-051 (“Cap B under voltage (Cap A volts, Cap B volts)”): The voltage on one of the two input capacitor banks (bank B) has fallen below the normal operating limit. First check: Check the input power (voltage and frequency).

Updated 2026-09-17 · LogrobotLM reference

Description

The voltage on one of the two input capacitor banks (bank B) has fallen below the normal operating limit. This is normally caused by low input voltage or a missing phase (with 3 phase input power) but it could be caused by a faulty switch board, main capacitor, contactor, or V-to-F feedback signal.

Remedy

Check the input power (voltage and frequency). Verify the primary reconnect is properly configured for the input voltage.

Related codes

LECO-024ArcLink mapping failedLECO-050Cap A under voltage (Cap A volts, Cap B volts)LECO-052Cap A over voltage (Cap A volts, Cap B volts)LECO-053Cap B over voltage (Cap A volts, Cap B volts)

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