Robotics in Manufacturing
SRVO-074

SRVO-074: LDAL alarm (pulse coder LED broken)

The LED inside the optical encoder has failed - the encoder can no longer read its own disc.

What it means

The LED inside the optical encoder has failed - the encoder can no longer read its own disc. No troubleshooting ladder on this one; it's a hardware death certificate.

Common causes

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

  1. Failed LED in the pulse coder. That's the list.

How to fix it

  1. Replace the pulse coder (motor), then perform mastering. Power-cycle to clear.

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