matsuura spindle motor problem

[thespindoc]

I have a Matsuura CNC mill MC-1000VS which is having a problem with the contactor for the spindle motor. It cycles on and off even when the computer section is off. I am wondering if the contactor switch itself could be worn out. If I leave is for a long time, after switching on and off it finally calms down and only does it occasionally. It is a serious problem though, to be machining and have the spindle turn off momentarily. I have already ruined 2 holders. When I watch the contactor I can see that a large spark is produced as it cycles. Should I remove it and inspect the contacts or just replace it and see what happens? Not sure if some other electronics are causing the switch to turn on and off but the spark concerns me that there may be a poor contact.

Since this recycling on and off occurs when the control section is turned off, I am wondering if the caps in the drive could still be considered the culprit?

Thanks for any suggestions
Keith

[Al_The_Man]

Trace the coil circuit and measure coil voltage when it happens WRT neutral.
Al.

[thespindoc]

Thanks, I will see if I can get to the circuit parts to the contactor as they are under a large circuit board...