What the C50A102 alarm means

The 48 V robot supply failed to reach the acceptable level during the power-up ramp; joints cannot be enabled. This is one of the faults our repair team handles on Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Weak or failing 48 V power supply unit
  • Excessive inrush load from a partially shorted joint motor
  • Bad power cable between supply and control box
  • Aging supply capacitors
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. Do a complete reboot sequence (full power-off, wait, power-on)
  2. Check the power cable and connections between power supply and control box
  3. Measure the 48 V output under load
  4. Disconnect peripherals and retry to isolate the load
  5. Replace the power supply if the ramp still fails
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 Drive & Power Stage alarms

C55A34 — Current Distributor / Safety Relay Error C72A2 — Power Supply Cannot Deliver 48V
Other brands: we also keep field-fix libraries for Kawasaki · Staubli · Epson and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Universal Robots C50A102 alarm mean?

The 48 V robot supply failed to reach the acceptable level during the power-up ramp; joints cannot be enabled. In field practice it belongs to the drive & power stage family of faults.

QCan I clear a Universal Robots C50A102 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 Universal Robots documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Universal Robots.