Velocity Control Alarm #7

[Doubleddaved]

I have a older Mazak V-10 with a 7M Fanuc controller.After running a couple of hours I get a #7 alarm which is a servo alarm.(velocity control unit alarm).I can clear it by hitting the clear button and starting over,but 15mins.later it happens again.I notice that this velocity controll unit gets pretty hot. This happens to be for the z axis. What could be causing this to get this hot and shutting down this drive? Thanks for all and any help.
Dave

[Al_The_Man]

Is there any Z axis counter-balance system fitted ? If so it may be that the axis is trying to support the full load of the head.
Al.