What the 9720 alarm means

When controller power was applied, an axis was detected moving too fast (e.g. the robot was falling or being pushed while unpowered); the encoder sees motion at startup and faults. This is one of the faults our repair team handles on Epson RC90 / RC700 (EPSON RC+) systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Axis moved while unpowered (brake released manually, gravity drop)
  • Robot pushed while powered off
  • Encoder glitch at power-on
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. Stop the robot and reboot the controller
  2. Inspect whether any axis physically moved while unpowered
  3. If a gravity axis dropped, support it, release the brake properly and re-home
  4. Check the brake on the affected axis
  5. If nothing moved, check encoder wiring and reboot again
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains, brakes or drive power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

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Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related System & Program alarms

4100 — Communication Error in Motion Control Module 4105 — Emergency Connector Connection Failure 4150 — Redundant Input Signal Failure of Emergency Stop 4152 — Relay Welding Error of Main Circuit 4154 — Regeneration Resistor Overtemperature 5040 — Motor Torque Output Failure — High Power State
Other brands: we also keep field-fix libraries for Nachi · Omron · ESTUN and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Epson 9720 alarm mean?

When controller power was applied, an axis was detected moving too fast (e.g. the robot was falling or being pushed while unpowered); the encoder sees motion at startup and faults. In field practice it belongs to the system & program family of faults.

QCan I clear a Epson 9720 alarm myself?

Sometimes. Work through the step-by-step checks on this page — the first listed cause is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power, brakes or safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1-3 business days, and worldwide within 2-5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

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 Epson documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Epson.