What the 4150 alarm means

The two redundant channels of the emergency stop input disagreed for more than two seconds; the safety system does not trust the E-stop state. This fault ranks high in our Epson RC90 / RC700 (EPSON RC+) service records, and the first site inspection usually finds the source.

Most common causes

  • One E-stop channel wired wrong or broken
  • Contact bounce or aging in a dual-channel E-stop device
  • Disconnection or earth fault on one channel
  • Timing skew between the two channels
Field note: The first cause shows up most on real machines, so verify it before you go further.

Step-by-step field fix

  1. Measure both redundant channels at the EMERGENCY connector while pressing/releasing each E-stop
  2. Look for disconnection, earth fault or short-circuit on either channel
  3. Replace dual-channel E-stop devices that switch unevenly
  4. Fix wiring so both channels open and close together
  5. Reboot the controller once the signals agree
Safety first: For EPSON 4150, 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. The self-serviceable action is Measure both redundant channels at the EMERGENCY connector while pressing/releasing each E-stop; anything past that falls under the e-stop chain and safety circuit and needs a certified engineer.

How we diagnose safety-chain faults on site

EPSON 4150 belongs to the safety chain & e-stop family. On EPSON 4150 the failing stage is safety circuit plus safety-function options on the RC700-A / RC90-B and the RC series - continuity of one series loop: e-stop buttons, door switches, light curtains, safety relays and the enabling device. We start reading EPSON 4150 at the EPSON RC+ error list and controller front-panel indicators; codes segment as 4xxx / 5xxx / 9xxx.

The chain involved in EPSON 4150 runs: e-stop / door / curtain -> safety relay (dual channel) -> controller safety input -> motor-off and brake apply.

On EPSON 4150 the field usually reports One E-stop channel wired wrong or broken, 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 EPSON 4150 (Redundant Input Signal Failure of Emergency Stop); written by the Henghuan repair team, updated 2026-10-01.

Not sure? Don't force it — contact an engineer

Tell us these three: alarm code, robot model, and the operating condition at the alarm. EPSON 4150 is a diagnosis our engineers do daily, and phone/video remote diagnosis is free.

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Related Safety Chain & E-Stop alarms

4105 — Emergency Connector Connection Failure
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 Nachi · Omron · ESTUN and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the EPSON 4150 alarm mean?

The two redundant channels of the emergency stop input disagreed for more than two seconds; the safety system does not trust the E-stop state. This fault ranks high in our Epson RC90 / RC700 (EPSON RC+) service records, and the first site inspection usually finds the source. EPSON 4150 sits in the safety chain & e-stop family; on our work orders the highest-frequency trigger for this code is "One E-stop channel wired wrong or broken".

QCan I clear a EPSON 4150 alarm myself?

Whether EPSON 4150 clears on its own depends on the outcome of "Measure both redundant channels at the EMERGENCY connector while pressing/releasing each E-stop". Finish the flow with "Reboot the controller once the signals agree" to confirm EPSON 4150 - do not skip it. If that step is clean, the second most frequent cause on EPSON 4150 is "Contact bounce or aging in a dual-channel E-stop device". Two attempts and still there means stop: EPSON 4150 involves the e-stop chain and safety circuit, and running EPSON 4150 on can turn a repairable fault into a replacement.

QA safety-chain fault like EPSON 4150 stops the line - how fast can you be here?

The commonest causes we see on EPSON 4150 are "One E-stop channel wired wrong or broken, Contact bounce or aging in a dual-channel E-stop device, Disconnection or earth fault on one channel", so we stock the van against those. For EPSON 4150 specifically, we stock along the loop: safety relays, common door switches, e-stop buttons, light-curtain pairs and terminal blocks. For EPSON 4150, 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 EPSON 4150 shows on the EPSON RC+ error list and controller front-panel indicators; codes segment as 4xxx / 5xxx / 9xxx and what the machine was doing - phone or video triage is free.

The content on EPSON 4150 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 Epson documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by Epson.