What the SRVO-075 alarm means

The pulse coder position changed while the controller was powered off, so the stored position no longer matches the actual mechanical position. We are very familiar with this alarm on FANUC R-30iA / R-30iB / R-30iB Plus systems — usually the first on-site inspection is enough to confirm the cause.

Most common causes

  • Axis moved by external force while power was off (brake released, manual push)
  • Backup battery failed and data was partially lost
  • Motor or pulse coder replaced
Field note: Our ticket data shows the first cause is by far the most common — start there to avoid dead ends.

Step-by-step field fix

  1. Do NOT run production - the robot may move to wrong positions
  2. Set $MASTER_ENB = 1, press RES_1PA, cycle power
  3. Re-master the affected axis (zero mastering or quick mastering)
  4. Verify with a known reference point or fixture before releasing to production
Safety first: For FANUC srvo-075, battery swaps carry reverse-polarity and short-circuit risk that can burn the measuring board; and a dead battery means lost zero data and a stopping re-master. The self-serviceable action is Do NOT run production - the robot may move to wrong positions; anything past that falls under battery polarity and zero data and needs a certified engineer.

How we diagnose calibration alarms on site

FANUC srvo-075 belongs to the battery & mastering family. On FANUC srvo-075 the failing stage is absolute encoders inside alpha-i motors, position memory held by the encoder battery pack on the R-30iB Plus / R-30iB Mate Plus / R-30iA - low battery voltage losing the absolute position memory, which then demands a fresh zero master - two jobs in one. We start reading FANUC srvo-075 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-075 runs: battery pack supply -> absolute position count -> memory held across power-off -> voltage too low loses it -> re-master required.

Once FANUC srvo-075 has lost zero data there are several recovery paths: When zero data is already lost there are several recovery paths with different cost and accuracy. The standard one is a fresh master with fixtures: best accuracy, needs a stop. Some models allow a coarse restore from mechanical datum marks or factory indices, enough to move again while a precision master is scheduled. And if the customer kept earlier calibration data or program backups, a straight restore may apply. We recommend by production urgency: coarse restore to keep running, precision master in the next window.

Field notes on this page cover FANUC srvo-075 (Pulse Position Mismatch); written by the Henghuan repair team, updated 2026-10-01.

Can't clear it yourself? Contact us for remote diagnosis

Tell us the alarm code, the model and what the machine was doing when the alarm appeared. FANUC srvo-075 FANUC srvo-075 is an everyday diagnosis for our engineers, and remote diagnosis (phone or video) costs nothing.

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Related Battery & Mastering alarms

SRVO-062 — BZAL Alarm (Group / Axis) SRVO-065 — BLAL Alarm - Battery Voltage Low SRVO-027 — Robot Not Mastered SRVO-038 — Pulse Mismatch (Group / Axis)
Same family: this code belongs to the Battery & mastering alarms family - the page collects all Battery & mastering-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-075 alarm mean?

The pulse coder position changed while the controller was powered off, so the stored position no longer matches the actual mechanical position. We are very familiar with this alarm on FANUC R-30iA / R-30iB / R-30iB Plus systems — usually the first on-site inspection is enough to confirm the cause. FANUC srvo-075 sits in the battery & mastering family; on our work orders the highest-frequency trigger for this code is "Axis moved by external force while power was off (brake released, manual push)".

QCan I clear a FANUC srvo-075 alarm myself?

Whether FANUC srvo-075 clears on its own depends on the outcome of "Do NOT run production - the robot may move to wrong positions". Finish the flow with "Verify with a known reference point or fixture before releasing to production" to confirm FANUC srvo-075 - do not skip it. If that step is clean, the second most frequent cause on FANUC srvo-075 is "Backup battery failed and data was partially lost". If FANUC srvo-075 returns after two clears, or the checks point at Axis moved by external force while power was off (brake released, manual push), stop the cell and call a professional robot repair engineer.

QWhen you handle FANUC srvo-075, will my programs and frames get lost?

The commonest causes we see on FANUC srvo-075 are "Axis moved by external force while power was off (brake released, manual push), Backup battery failed and data was partially lost, Motor or pulse coder replaced", so we stock the van against those. For FANUC srvo-075 specifically, we carry the model's battery pack and mastering fixtures; battery changes belong in scheduled maintenance, not in alarm response. For FANUC srvo-075, on battery and mastering alarms we back up programs and points first, master second and verify precision on site. Before we roll, tell us what FANUC srvo-075 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 content on FANUC srvo-075 was written by Henghuan Robotics service engineers from hands-on repair experience. Alarm descriptions are our own reference summary and may differ by controller or software version — defer to FANUC documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by FANUC.