What causes FANUC alarm 5136?

One or more servo amplifiers lost power or were not powered on before the CNC control initialized. A fiber optic FSSB cable is disconnected, damaged, or seated poorly between amplifiers. A servo amplifier has failed internally and is not responding on the FSSB network. Parameter settings for the number of axes or amplifiers do not match the actual hardware connected. A newly added or replaced amplifier was not properly recognized after a configuration change.

How do I fix FANUC alarm 5136?

1. Check that all servo amplifiers in the cabinet have their status LEDs lit and are fully powered on before the CNC boots up. A dark or faulted amplifier will not appear on the FSSB. 2. Inspect every fiber optic FSSB cable connection starting from the CNC axis card through each amplifier in the chain. Reseat any loose connectors and look for bent, cracked, or dirty fiber tips. 3. Verify the FSSB amplifier count in parameters matches the physical hardware. On Fanuc Series 30i/31i/32i check parameters 1902 and 1905 series; on 0i-D/F check parameter 1023 and FSSB setting screen under the system menu. 4. Power cycle the entire machine with all amplifiers confirmed healthy, then re-enter the FSSB automatic setting screen and allow the control to re-detect amplifiers. Save the new configuration if prompted. 5. If one amplifier is suspected faulty, swap it with a known good unit of the same type and retest. A failed amplifier breaks the FSSB chain and causes all downstream amplifiers to also go undetected.

axismd.ai

FANUC Controller

Servo/Axis · Intermediate · 30-90 minutes

Alarm 5136

Fanuc Alarm 5136 - FSSB: NUMBER OF AMPS IS SMALL

Alarm 5136 occurs when the CNC detects fewer servo amplifiers on the FSSB (Fiber Optic Servo Serial Bus) network than are configured in parameter 8130 (number of amplifiers). This indicates a communication failure, amplifier power loss, or incorrect parameter configuration on 30i/31i/32i/0i-F systems using FSSB.

FANUCServo/AxisIntermediate30-90 minutes

5136

Fanuc Alarm 5136 - FSSB: NUMBER OF AMPS IS SMALL

SERVO ALARM 5136

Root Cause Summary

Alarm 5136 occurs when the CNC detects fewer servo amplifiers on the FSSB (Fiber Optic Servo Serial Bus) network than are configured in parameter 8130 (number of amplifiers). This indicates a communication failure, amplifier power loss, or incorrect parameter configuration on 30i/31i/32i/0i-F systems using FSSB.

Causes and Fixes

1
Check all servo amplifier LED displays. Normal operation shows green POWER LED and FSSB Link LED. Note any amplifiers with red ALM LED or no LEDs illuminated.
2
Verify DC bus voltage at each amplifier. Check incoming 3-phase AC power to the power supply module and confirm DC bus voltage is within specification (typically 280-325VDC for 200V class, 530-680VDC for 400V class).
High voltage present. Follow lockout/tagout procedures.
3
Check amplifier control power supply connections (24VDC). Verify 24VDC is present at CN1 connector on each amplifier using a multimeter.
4
Navigate to SYSTEM > DIAGNOSIS > SERVO and check diagnostic screen #300-#30F for amplifier status. Missing amplifiers will show '--' or no data. Compare with parameter 8130 to identify which axis amplifier is offline.

DIY Feasiblehigh confidence

Call a technician if:

·Amplifier replacement required
·Multiple amplifiers affected simultaneously
·Parameter backup/restore needed

Prevention

Regular FSSB cable inspection during PM
Monitor parameter 1815 DC bus voltage trends
Maintain proper cable routing away from interference sources
Document amplifier FSSB addresses for quick troubleshooting

Common Mistakes

Forgetting FSSB chain termination
Mixing FSSB cable types
Not checking control power before DC bus power
Changing parameters without backup

Related Alarms

5135 5137 5140 5141

Seeing Multiple Alarms?

Seeing another alarm with this one? Enter the code.

Get machine-aware diagnosis

AxisMD logs alarms against your actual machines, tracks patterns, and gives AI context your manual doesn't have.

Start free

Was this guide helpful?

Always verify with your machine manual or a certified technician before performing service procedures.