Here is a (hopefully) clearer description of the problem.
I've moved my Nakamura lathe with Fanuc 5T controller to another property and let it sit for a year.
It boots up properly but the spindle drive behaves badly
Following are the symptoms;
When I use the control panel to start the spindle, and the speed knob is in the lowest position, the motor turns on and makes a mild growling sound.
If I then turn the spindle speed knob quickly, the circuit trips and I get an alarm on the spindle drive board "over current/ field loss" after which I turn the power supply off then on again and re-boot the machine.
After starting the spindle again, when I turn the knob slowly to increase the speed, the motor follows but is a little rough sounding and it doesn't reach as high a speed as it used to nor accelerates as fast as it used to, ie: the motor doesn't keep up with the knob position. If the spindle is at 2000 RPM and I turn the knob to <full> (3000RPM) the spindle speed will increase over 20 seconds to only 2500 RPM . It sounds OK at that point.
If I press the spindle stop button at that point, or at any time when the spindle speed is above ~300 RPM, the circuit shuts down and I get the same alarm.
If the spindle is at any higher speed and I turn the knob quickly to reduce the speed, the circuit shuts down and I get the same alarm
If the spindle is running at high speed and I SLOWLY turn the knob to reduce the speed to around 300 RPM and then press the spindle stop button, the spindle stops as it should.
Would anyone be able to guide me on this problem?