I have an MV40 with Fanuc controls that is has alarm 12 which has to do with cables,motor or amp short.I've checked the cables and motor with a megger with good readings.Sent in the amp for repair and Fanuc had to do "minor" repairs but tested ok---until I got it back in the machine.Any thoughts??

Does it have the alarm 12 at power up?

If so remove the output wires to the motor and power up again and see if the alarm is still there.

Another quick test would be to run the spindle as slow as you can and check to see if it is smooth or not.

It is still possible the drive could be defective.

RRL

Alarm 12 on a Fanuc AC spindle drive means that excess current flowed in the drive. If the board is good, there is most certainly a shorted power transistor module. Fanuc's spindle maintenance manual has a few pages on how to test the modules. Be careful when changing the modules - the wires aren't marked.

Warren
www.uptimecorp.com