FANUC Alarm SRVO-057 — SERVO FSSB disconnect
Error- Hardware
- fuses
- Controllers
- R-J3iB / R-30iA / R-30iB
- FANUC class
- SERVO2
Manufacturer wording — SERVO FSSB disconnect (G:%d A:%d)
The manual prints placeholders; your controller fills them in with the real group, axis or number.
FANUC SRVO-057 (“SERVO FSSB disconnect”): The FSSB communication from SLAVE to SRVO is disconnected. First check: 1. Check cable COP10A that connects the servo amplifier to the main CPU board.
Updated 2026-10-22 · LogrobotLM reference
Description
The FSSB communication from SLAVE to SRVO is disconnected.
Remedy
1. Check cable COP10A that connects the servo amplifier to the main CPU board. 2. Check fuse F3 on the PSU PCB.WARNING: Before you continue to the next step, perform a complete controller backup to save all your programs and settings from memory for this robot. After you complete the next step, restore the saved data to the new main CPU board if memory has been lost. Otherwise, you could injure personnel, damage equipment, or lose
Field diagnosis
Communication between the main board and the amplifier is cut: power supply or amplifier fuse blown, fiber disconnected or broken.
What to check
- Check the power supply unit fuse and the amplifier fuse FS1 (on R-30iB, a blown FS1 requires replacing the complete amplifier); check and replace the fiber; then axis control board, then amplifier (full backup before replacing a board).
- Note: An amplifier that does not light up at all gives 057, not 055/056.
Related codes
Indicative field information — the robot manufacturer's manual and safety procedures always prevail. Never bypass a safety device; apply lockout/tagout (LOTO) before any physical intervention. How this reference is built →