Hi everyone.
I have the same problem with my machining center. It has a Fanuc 0m control and the 401 servo alarm (VRDY OFF) message comes right at machine startup. I just bought the machine and the seller said there was no alarms before they disconnected the hydraulic unit. After they reconnected the hyd unit, the message appeared. He said that it's probably because theres air in the oil system but I doubt it. Besides I have let all the air out of the oil tubes.
The machine starts normally but after a few seconds a relay clicks and this message appears. I measured some voltages from the power unit module and found out that the module does not have power because the main relay does not work, uknow the really big one right after the main power switch and transformer that is driven by the power unit itself. I manually pressed the relay so that all the modules had power but it had no effect whatsoever. The same 401 message appears.
The servo- or the spindle driver's alarm leds are not lid, but the spindle driver has been changed to a re-built one so im not 100% sure if theres some compatibility problems. But the driver is not broken, it is guaranteed, and there was no alarm when the driver was changed, it appeard later.
Also no axis limits are pressed because none of the axis are close to the ends and I can hear a relay click by pressing emergency button, and the electric charts say the limit switches are serial connected to the emergency button.
Any ideas, anyone?