SRVO-059

Identify which axis failed initialization

On the teach pendant, press MENU → ALARM → F1 [TYPE] → Select 'Servo Alarms'. Look for the specific axis number in the alarm detail (e.g., 'Axis 1' or 'Axis J4'). Record which amplifier(s) are affected.

Multiple axes showing the same alarm simultaneously usually indicates a main FSSB trunk issue rather than individual amplifier problems.

Inspect FSSB fiber optic cables and connections

Power down the controller. Open the cabinet and visually inspect all FSSB fiber optic cables (orange cables) from the CPU board to each servo amplifier. Check for: bent fiber tips, loose connectors, damaged cable jackets, and proper seating in both CPU FSSB ports and amplifier FSSB IN/OUT ports. Clean fiber tips with approved optical cleaner if dusty.

Never look directly into fiber optic cable ends when system is powered on. Laser light can damage eyes.

Verify FSSB loop continuity and termination

Trace the complete FSSB loop: CPU FSSB OUT → Amp 1 IN → Amp 1 OUT → Amp 2 IN → continuing through all amplifiers → final Amp OUT returns to CPU FSSB IN. Ensure the loop is complete with no breaks. The last amplifier in the chain should have its OUT port connected back to the CPU, creating a closed loop.

On robots with dual-check safety, verify both FSSB Channel A and Channel B are properly looped. A break in either channel can cause initialization failure.

Check FSSB status LEDs on CPU and amplifiers

During power-up, observe the FSSB LED on the main CPU board and each servo amplifier. During initialization, they should flash rapidly then go solid green. Red FSSB LED or no LED activity indicates communication failure at that point in the loop. If an amplifier's FSSB LED is red/off, the issue is likely at that amplifier or the cable immediately upstream.

The FSSB LED pattern during boot is critical: rapid flashing (initializing), solid green (communication OK), solid red (communication error), off (no signal received).

Test with replacement FSSB cables

If a specific cable segment is suspect, swap it with a known-good FSSB cable of the same length. FSSB cables are not generic fiber; use only Fanuc-certified cables. After replacement, power cycle completely (disable main circuit breaker for 30 seconds) and observe initialization.

Always power down completely before connecting or disconnecting FSSB cables to prevent data corruption or component damage.

Read amplifier fault codes from teach pendant

Navigate to MENU → MAINTENANCE → F1 [TYPE] → 'Servo Monitor'. Select each axis individually and look for error codes or status information. Also check MENU → SYSTEM → Variables → $SCR.$SERVO_ALARM[n] where n is the axis number. Note any additional error codes displayed.

System variable $SCR_GRP[1].$SSV_INI_STS shows servo initialization status bitmap. A value other than 0 after startup indicates which amplifier(s) failed initialization.

Verify amplifier model and firmware compatibility

Open the cabinet and record the complete part number from the label on the affected servo amplifier (format: A06B-6xxx-Hxxx#xxxx). Compare against your robot's parts list or documentation. Check firmware version by accessing MENU → SYSTEM → Version ID → F4 [AMPLIFIER]. Firmware must be compatible with controller software version shown under MENU → SYSTEM → Version ID.

R-30iB Plus controllers require β series amplifiers with firmware V8.30 or later. Using older αi series amplifiers will cause initialization failures.

Inspect amplifier for visual fault indicators

During power-up, observe the LED indicators on the affected servo amplifier. Standard sequence: Power LED green, FSSB LED flashing then solid green, READY LED off during init then solid green when complete. Red LEDs, burned components, swollen capacitors, or unusual odors indicate hardware failure requiring amplifier replacement.

High voltage remains in servo amplifiers for several minutes after shutdown. Wait minimum 5 minutes and verify discharge before touching components.

Check amplifier configuration parameters

Access MENU → MAINTENANCE → F1 [TYPE] → Axis Config. Verify that parameters for the failing axis match the installed amplifier: $SV_AXIS_TYPE, $SV_AMP_TYPE, and $SV_MOTOR_TYPE. Incorrect configuration will prevent initialization. Compare with documentation or working axes.

If amplifier was recently replaced, parameters may need to be reconfigured. Always back up servo parameters before amplifier replacement using MENU → FILE → Backup.

Perform amplifier firmware update if needed

If firmware incompatibility is confirmed, obtain correct firmware from Fanuc. Load firmware onto USB device and insert into teach pendant. Navigate to MENU → MAINTENANCE → F1 [TYPE] → Amplifier Firmware Update. Follow on-screen prompts. This requires system password and controlled images file from Fanuc matching your controller version.

Incorrect firmware can permanently damage amplifiers. Verify exact part numbers and firmware version compatibility with Fanuc before updating. Never interrupt power during firmware update.