I've got a Miyano ANC-45, circa 1986, with two turrets, a subspindle and live tooling on the main turret (main spindle positioning only, not a full C-axis and not on the sub). The control is a Fanuc 11TT.

The sub spindle drive is currently giving me an alarm. The drive is a Fanuc A06B-6052-H002. The alarm LED's on the drive are indicating Alarm #2, which the drive manual describes as "Speed is deviated from the command value". The funny thing is, that alarm lights up the instant there is power to the drive, before the CNC control is even turned on. The LED lights up at the same moment the green power LED does. At that point I wouldn't have thought there would even be a "command value" for the speed to deviate from.

There is an encoder on the spindle, separate from the motor. With the CNC control on, turning the spindle by hand does change the speed readout on the CNC in an apparently accurate manner, so it looks like that encoder is working. The DC voltages at all the check terminals on the drive associated with the motor's speed sensors seem to be in the right ballpark; I just ordered an oscilloscope, so I can check that more properly this weekend.

The manual also mentions some fuses, the Transistor Module, and the regeneration circuit as possible causes for this alarm. The fuses are all good, and the regen resistor measures at 15 ohms, which is correct. I checked out the transistor module the best I could with a multimeter; all 6 transistors in there measured the same for voltage drop, and nothing seemed too far out of line.

Needless to say, I'm having trouble figuring this one out. Has anyone ever seen anything like this before?

Thanks in advance.