Robotics in Manufacturing
SRVO-047

SRVO-047: LVAL alarm (low control voltage)

The low-voltage control supply (+5V etc.) inside the servo amplifier dropped below spec - the amplifier's own electronics aren't being fed properly.

What it means

The low-voltage control supply (+5V etc.) inside the servo amplifier dropped below spec - the amplifier's own electronics aren't being fed properly. Posts per amplifier; power-cycle to clear.

Common causes

Ranked by what technicians most often find, most likely first.

  1. Power supply unit fault.
  2. Servo amplifier fault.
  3. Wiring between PSU and amplifier.

How to fix it

  1. Cycle power once - transient supply dips happen.
  2. On recurrence, this is a PSU/amplifier diagnosis per the controller maintenance manual: check the amplifier's control-voltage LEDs and the PSU outputs before swapping parts.

Quick facts

Category
Servo
Affected series
R-30iB; R-30iB Mate; R-30iB Plus; R-30iB Mate Plus
Alarm family
SRVO

Related codes

Verified against FANUC documentation (B-83284EN-1).Last reviewed: 2026-07-09.Editorial process