What the SRVO-157 alarm means

The DC link charge circuit in the amplifier failed to charge the bus capacitors within the expected time at power-up. This is a routine repair in our workshop for FANUC R-30iA / R-30iB / R-30iB Plus systems, and we normally pin it down during the first site check.

Most common causes

  • Charge resistor or charge contactor failure inside the amplifier
  • Input power problem (phase loss, low voltage)
  • Aged DC link capacitors
Field note: Begin with the first item in the list; it has a far higher on-machine occurrence rate than the others.

Step-by-step field fix

  1. Verify incoming 3-phase power
  2. Cycle power once - if persistent, the amplifier needs repair/replacement
  3. On high-hour controllers, plan capacitor/amp overhaul proactively
Safety first: For FANUC srvo-157, amplifiers and boards are live parts: hot-plugging a board burns interface circuits, and body static can kill sensitive devices. What you can check yourself first is Verify incoming 3-phase power; live boards and power devices handling is not a DIY job.

How we diagnose amplifier/hardware alarms on site

FANUC srvo-157 belongs to the amplifier & hardware family. On FANUC srvo-157 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-157 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-157 runs: control-side signal -> amplifier board (drive and sense circuits) -> fuses and supply -> cooling -> motor-side output.

When FANUC srvo-157 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-157 (CHARGE Alarm); written by the Henghuan repair team, updated 2026-10-01.

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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-157 alarm mean?

The DC link charge circuit in the amplifier failed to charge the bus capacitors within the expected time at power-up. This is a routine repair in our workshop for FANUC R-30iA / R-30iB / R-30iB Plus systems, and we normally pin it down during the first site check. FANUC srvo-157 sits in the amplifier & hardware family; on our work orders the highest-frequency trigger for this code is "Charge resistor or charge contactor failure inside the amplifier".

QCan I clear a FANUC srvo-157 alarm myself?

Whether FANUC srvo-157 clears on its own depends on the outcome of "Verify incoming 3-phase power". Finish the flow with "On high-hour controllers, plan capacitor/amp overhaul proactively" to confirm FANUC srvo-157 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-157 is "Input power problem (phase loss, low voltage)". If FANUC srvo-157 returns after two clears, or the checks point at Charge resistor or charge contactor failure inside the amplifier, stop the cell and call a professional robot repair engineer.

QFor hardware alarms like FANUC srvo-157, does it always mean an expensive part swap?

The commonest causes we see on FANUC srvo-157 are "Charge resistor or charge contactor failure inside the amplifier, Input power problem (phase loss, low voltage), Aged DC link capacitors", so we stock the van against those. For FANUC srvo-157 specifically, we carry fuses, filter mats, common connectors and terminals; boards are stocked by type or go through the repair channel. For FANUC srvo-157, on hardware alarms we inspect before quoting - we do not open with replace the power stage. Before we roll, tell us what FANUC srvo-157 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.

This page on FANUC srvo-157 was written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller and software version — when in doubt, check your FANUC documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by FANUC.