SRVO-057

Identify the Affected Axis

On the teach pendant, navigate to MENU > ALARM > F1 [DETAIL] to view the full alarm history. Note which axis number appears in the alarm detail (e.g., 'Axis 3 FSSB disconnect'). Check MENU > SYSTEM > Variables > $SCR_GRP[1].$axis_alarm to identify the specific axis group and amplifier.

The alarm will typically show the first axis that dropped from the chain, but all axes downstream in the FSSB loop will also be offline. Check the physical amplifier order in the cabinet.

Inspect Fiber Optic Connectors at Affected Amplifier

Open the electrical cabinet and locate the affected servo amplifier. Inspect both the IN and OUT fiber optic connectors (typically orange/grey SC-type connectors). Check for loose connections, dust/contamination on connector faces, or visible damage. Remove and reseat each connector firmly until you hear/feel a click.

Never look directly into fiber optic cable ends with the system powered on. Laser radiation can cause eye damage.

Inspect Fiber Optic Cable Routing

Trace the entire FSSB fiber cable path from the controller through each amplifier in the chain. Look for pinched cables, sharp bends (minimum bend radius is 30mm), cable tie over-tightening, or cables routed near moving parts or cabinet doors. Check for any signs of cable jacket damage or stress at connector boots.

FSSB cables should be routed away from power cables and have service loops at connections to prevent stress. Mark the cable routing with tape for future reference.

Verify FSSB Communication Restoration

After reseating connections, power cycle the controller. Navigate to MENU > SYSTEM > F1 [TYPE] > Servo Disconn to view FSSB connection status. All configured axes should show 'Connected'. Check parameter 19000-19007 (Servo Serial Number) to verify all amplifiers are detected with their correct serial numbers.

If the alarm recurs immediately or intermittently, replace the suspect fiber cable. Keep spare FSSB cables of appropriate lengths in your service kit.

Check Amplifier LED Status Indicators

Examine the front face of the suspected servo amplifier for LED indicators. A normally operating α/β-series amplifier shows green LEDs. Red LEDs, flashing patterns, or no LEDs indicate a fault. Document the LED pattern and refer to the amplifier manual for specific fault codes. Common patterns: solid red = overcurrent, flashing red = overheat, no LED = no power.

Do not touch amplifier components with power applied. High voltage DC bus capacitors remain charged for several minutes after power removal.

Verify Amplifier Input Power

With the system powered off and LOTO applied, check the 200-230VAC 3-phase input power to the amplifier. Use a multimeter to verify all three phases (R, S, T) have proper voltage and are balanced within 2%. Check for blown fuses in the input circuit. For the DC bus, verify the DC link voltage is approximately 280-320VDC when powered (check at test points if available).

Check the power supply module or PSM (Power Supply Module) shared by multiple amplifiers. One PSM typically powers 2-4 axes. A PSM failure will affect multiple amplifiers simultaneously.

Review Amplifier Alarm History

Navigate to MENU > ALARM > F5 [SERVO] on the teach pendant to view servo-specific alarm history. Look for alarms that occurred immediately before the FSSB disconnect, such as SRVO-050 (overload), SRVO-062 (excess regen), or SRVO-075 (overheat). These indicate the amplifier shut itself down due to a protective fault.

Parameter 19004 (Amplifier type) and 19005 (Amplifier software version) should match the physical amplifier. A mismatch indicates a replaced amplifier that wasn't properly configured.

Perform Amplifier Substitution Test

If a specific amplifier is suspected, swap it with a known-good amplifier of the same type. Update MENU > SYSTEM > Master/Cal > Servo ID to reassign axis connections if necessary. Power cycle and observe if the problem follows the amplifier (amplifier fault) or stays with the position (external issue).

Ensure replacement amplifiers match the original part number and power rating. Mismatched amplifiers can cause immediate motor damage.

Check Amplifier Configuration Parameters

Verify amplifier configuration in MENU > SYSTEM > F1 [TYPE] > F1 [Servo]. Check that parameter 19000-19007 matches the physical installation. Parameter 19001 (Amp type) must match the actual amplifier model. If recently replaced, the amplifier may need initialization via MENU > SYSTEM > Master/Cal > Initial Setup.

After replacing an amplifier, always perform a master/calibration backup and update the serial number records. Keep a log of all amplifier serial numbers for future diagnostics.