Fanuc alarm
The servo amplifier never said it was ready, or it dropped its ready signal (VRDY).
The servo amplifier never said it was ready, or it dropped its ready signal (VRDY). The control won't move any axis until every amplifier on the loop reports ready. SV0401 is usually a symptom: something else stopped the amplifier from powering up.
Lock out the machine before reaching into it. Never bypass a door switch or interlock to clear an alarm.
If the amp display shows an alarm code, or the contactor isn't pulling in with the E-stops clear, call a tech who works on Fanuc drives. Testing the incoming power and contactor means working inside a live cabinet.
CNC, press brake and full machine repair across Illinois and Wisconsin
Alignment & Laser Calibration · Control & Electronics Repair · Crash Recovery · Hydraulics & Lubrication · Machine Moving & Installation · Press Brake & Fab Equipment
On-site CNC and plant equipment repair across Illinois, with 30+ years of tech experience
Control & Electronics Repair · Crash Recovery · Hydraulics & Lubrication · Press Brake & Fab Equipment · Preventive Maintenance · Retrofits & Control Upgrades
Wisconsin-owned CNC repair with teams in Milwaukee, Madison and Green Bay
Control & Electronics Repair · Crash Recovery · Hydraulics & Lubrication · Press Brake & Fab Equipment · Preventive Maintenance · Retrofits & Control Upgrades
The servo amplifier never said it was ready, or it dropped its ready signal (VRDY). The control won't move any axis until every amplifier on the loop reports ready. SV0401 is usually a symptom: something else stopped the amplifier from powering up.
Emergency stop circuit open (an E-stop button, door switch or overtravel in the chain). The amplifier's main contactor (MCC) did not pull in. Another amplifier or power supply alarm (check the amp's LED display). Missing or low 200V three-phase power into the power supply. Loose or damaged FSSB fiber optic cable.
Look at the 7-segment display on the power supply and each amplifier and write down any number or letter showing. Open the alarm history: the alarm just before SV0401 is often the real cause. Make sure every E-stop button is out and the doors are fully closed. Listen for the MCC contactor clicking in when you reset. Check that the main breaker and the transformer feeding the amps haven't tripped. If the amp display shows an alarm code, or the contactor isn't pulling in with the E-stops clear, call a tech who works on Fanuc drives. Testing the incoming power and contactor means working inside a live cabinet.
Alarm numbers and text can differ by control model, software version and machine builder. This page is a starting point from people who have worked on these machines, not a replacement for your machine builder's manual.
Free for shops that need a repair. We pass your request to repair techs who cover your area and fix your brand. They reach out to you directly.
The leading CNC machine repair directory and a leading machine shop and repair magazine. We help shop owners, consumers and manufacturers find trusted repair, and keep the industry informed with the latest news, trends and headlines. Run by people who have worked in machine shops and run maintenance.
