What the 4780 alarm means

The Functional Safety Unit (FSU) on the YRC1000 detects that the robot exceeded a configured safety limit — position range, speed, or orientation — and initiates a safe stop. Codes 4780-4799 are all FSU alarms. This is a fault we handle frequently on Yaskawa DX100 / DX200 / YRC1000 systems — in most cases we can pin down the root cause on the first site visit.

Most common causes

  • Robot jogged or played back into a forbidden zone defined in the safety settings
  • Speed limit for manual/reduced mode exceeded
  • Safety file out of sync after a backup restore or file transfer
  • Tool calibration mismatch making the monitored TCP position wrong
Field note: The first item on this list is what we hit most often on real machines — clear that one before going deeper.

Step-by-step field fix

  1. Jog the robot back inside the permitted zone in joint mode
  2. Check the safety settings (zone limits, speed limits) against the cell layout
  3. Verify the TCP/tool calibration matches the real tooling
  4. Re-load a consistent safety file if the FSU data was corrupted
  5. Power-cycle once after correcting the settings; if FSU alarms persist, contact a qualified safety engineer
Safety first: For YASKAWA 4780, this alarm is the safety circuit itself: jumpering a door switch or forcing a contactor removes the protection entirely - no protective action when something happens, and no defensible account of responsibility. On site you may look at after confirming power-off the first step yourself: Jog the robot back inside the permitted zone in joint mode. Beyond that it is the e-stop chain and safety circuit work - leave it to a professional.

How we diagnose safety-chain faults on site

YASKAWA 4780 belongs to the safety chain & e-stop family. On YASKAWA 4780 the failing stage is safety hold circuit plus functional-safety options on DX200 / YRC1000 on the DX100 / DX200 / YRC1000 / YRC1000micro - continuity of one series loop: e-stop buttons, door switches, light curtains, safety relays and the enabling device. We start reading YASKAWA 4780 at the pendant alarm list (A / E / 4xxx segments) together with the servo drive's digit display.

The chain involved in YASKAWA 4780 runs: e-stop / door / curtain -> safety relay (dual channel) -> controller safety input -> motor-off and brake apply.

On YASKAWA 4780 the field usually reports Robot jogged or played back into a forbidden zone defined in the safety settings, but the check that matters is not continuity: The point of a safety loop is not whether it conducts but whether both channels conduct together. The relay compares channels; if one opens tens of milliseconds early it latches as a channel fault. The commonest causes are plain: oxidised door-switch contacts raising contact resistance, or one loose terminal. We measure segment by segment - pendant e-stop, panel e-stop, external e-stop, safety door - and lock onto whichever segment reads differently on the two channels.

Field notes on this page cover YASKAWA 4780 (F-SAFE Error — Safety Range/Speed Limit Violation); written by the Henghuan repair team, updated 2026-10-01.

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Related Safety Chain & E-Stop alarms

1219 — Enable Switch Sticking (DX100/DX200/YRC1000)
Same family: this code belongs to the Safety chain & e-stop alarms family - the page collects all Safety chain & e-stop-family codes we have handled, with the common inspection order and spares.
Other brands: we also keep field-fix libraries for Universal Robots · Kawasaki · Staubli and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the YASKAWA 4780 alarm mean?

The Functional Safety Unit (FSU) on the YRC1000 detects that the robot exceeded a configured safety limit — position range, speed, or orientation — and initiates a safe stop. Codes 4780-4799 are all FSU alarms. This is a fault we handle frequently on Yaskawa DX100 / DX200 / YRC1000 systems — in most cases we can pin down the root cause on the first site visit. YASKAWA 4780 sits in the safety chain & e-stop family; on our work orders the highest-frequency trigger for this code is "Robot jogged or played back into a forbidden zone defined in the safety settings".

QCan I clear a YASKAWA 4780 alarm myself?

Whether YASKAWA 4780 clears on its own depends on the outcome of "Jog the robot back inside the permitted zone in joint mode". Finish the flow with "Power-cycle once after correcting the settings; if FSU alarms persist, contact a qualified safety engineer" to confirm YASKAWA 4780 - do not skip it. If that step is clean, the second most frequent cause on YASKAWA 4780 is "Speed limit for manual/reduced mode exceeded". After clearing YASKAWA 4780, watch it for one shift. A second trip means stop and let an engineer arrive with the right test gear for the e-stop chain and safety circuit.

QA safety-chain fault like YASKAWA 4780 stops the line - how fast can you be here?

The commonest causes we see on YASKAWA 4780 are "Robot jogged or played back into a forbidden zone defined in the safety settings, Speed limit for manual/reduced mode exceeded, Safety file out of sync after a backup restore or file transfer", so we stock the van against those. For YASKAWA 4780 specifically, we stock along the loop: safety relays, common door switches, e-stop buttons, light-curtain pairs and terminal blocks. For YASKAWA 4780, a safety-chain fault stops the whole line, so we rank it top priority and pre-triage by phone: door switch, e-stop or relay. Before we roll, tell us what YASKAWA 4780 shows on the pendant alarm list (A / E / 4xxx segments) together with the servo drive's digit display and what the machine was doing - phone or video triage is free.

The notes on YASKAWA 4780 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 Yaskawa documentation or contact us with questions. Henghuan is an independent service provider, not affiliated with or endorsed by Yaskawa.