What the SRVO-156 alarm means

The Intelligent Power Module (IPM) in the servo amplifier triggered its internal protection - overcurrent, overheating, or undervoltage inside the power stage. We fix this FANUC R-30iA / R-30iB / R-30iB Plus fault almost daily, and one round of on-site checks usually confirms what is going on.

Most common causes

  • Amplifier power stage failure
  • Motor winding or cable short stressing the IPM
  • Severe overload or stalled axis
  • Cooling failure (fan, heatsink dust)
Field note: We have tallied real cases: the first cause tops the list, so start your diagnosis there.

Step-by-step field fix

  1. Rule out motor/cable shorts first - replacing an amp into a short kills the new amp
  2. Check amplifier fan and heatsink
  3. Verify mechanical axis moves freely
  4. Replace the servo amplifier if the fault is internal
Safety first: For FANUC srvo-156, amplifiers and boards are live parts: hot-plugging a board burns interface circuits, and body static can kill sensitive devices. The self-serviceable action is Rule out motor/cable shorts first - replacing an amp into a short kills the new amp; anything past that falls under live boards and power devices and needs a certified engineer.

How we diagnose amplifier/hardware alarms on site

FANUC srvo-156 belongs to the amplifier & hardware family. On FANUC srvo-156 the failing stage is alpha-i / beta-i servo amplifiers with PSM supply modules and SVM servo modules (SPM where spindles fit) on the R-30iB Plus / R-30iB Mate Plus / R-30iA - the amplifier and drive hardware itself plus its periphery: boards, fuses, cooling, supply, connectors and self-test. We start reading FANUC srvo-156 at the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code.

The chain involved in FANUC srvo-156 runs: control-side signal -> amplifier board (drive and sense circuits) -> fuses and supply -> cooling -> motor-side output.

When FANUC srvo-156 fires, clear the external causes first - Many hardware alarms are not hardware at all but external conditions: a packed filter causing over-temperature, a missing phase causing undervoltage, a loose connector causing a communication drop. Our order clears the externals first - clean, replace the mat, measure supply, re-seat terminals - near-zero cost and a high hit rate. Only when externals are gone do we judge boards or power stage. It also keeps the quotation honest: we do not sell parts we have not earned.

Field notes on this page cover FANUC srvo-156 (IPMAL - IPM Alarm); written by the Henghuan repair team, updated 2026-10-01.

If you can't fix it, reach our engineers directly

Send the alarm code, the robot model and a description of what was happening at the alarm. Our engineers handle FANUC srvo-156 FANUC srvo-156 every day, and remote diagnosis by phone/video is free.

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Related Amplifier & Hardware alarms

SRVO-057 — FSSB Disconnect SRVO-068 — DTERR - Data Transmission Error SRVO-069 — CRCERR - CRC Error SRVO-071 — SPHAL - Soft Phase Alarm SRVO-072 — PMAL - Pulse Coder Phase Alarm SRVO-073 — CMAL - Pulse Coder Count Error
Same family: this code belongs to the Amplifier & hardware alarms family - the page collects all Amplifier & hardware-family codes we have handled, with the common inspection order and spares.
Other brands: see our KUKA, ABB, Yaskawa and Universal Robots field-fix libraries — or the full 10-brand hub.

Frequently asked questions

QWhat does the FANUC srvo-156 alarm mean?

The Intelligent Power Module (IPM) in the servo amplifier triggered its internal protection - overcurrent, overheating, or undervoltage inside the power stage. We fix this FANUC R-30iA / R-30iB / R-30iB Plus fault almost daily, and one round of on-site checks usually confirms what is going on. FANUC srvo-156 sits in the amplifier & hardware family; on our work orders the highest-frequency trigger for this code is "Amplifier power stage failure".

QCan I clear a FANUC srvo-156 alarm myself?

Whether FANUC srvo-156 clears on its own depends on the outcome of "Rule out motor/cable shorts first - replacing an amp into a short kills the new amp". Finish the flow with "Replace the servo amplifier if the fault is internal" to confirm FANUC srvo-156 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-156 is "Motor winding or cable short stressing the IPM". Do not chase takt through a repeating FANUC srvo-156. Left alone, amplifier & hardware faults tend to graduate from repairable to must-replace.

QFor hardware alarms like FANUC srvo-156, does it always mean an expensive part swap?

The commonest causes we see on FANUC srvo-156 are "Amplifier power stage failure, Motor winding or cable short stressing the IPM, Severe overload or stalled axis", so we stock the van against those. For FANUC srvo-156 specifically, we carry fuses, filter mats, common connectors and terminals; boards are stocked by type or go through the repair channel. For FANUC srvo-156, on hardware alarms we inspect before quoting - we do not open with replace the power stage. Before we roll, tell us what FANUC srvo-156 shows on the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code and what the machine was doing - phone or video triage is free.

The notes on FANUC srvo-156 were summarized by the Henghuan Robotics repair team from on-site service. The alarm interpretation is our empirical summary for troubleshooting reference and may vary by controller and software version — please check FANUC documentation or contact us with questions. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.