Hi. We have 1986 Mazak Quickturn10N with 12 post revolver and 22kW servo. We have had it two years, and following problem has been with it all the time, but has been getting worse, and now totally out of order.

When you put the chuch on, it either:
A. says "iuk" and turns coupole of mm and stops. or says "iuk-iuk-iuk-iuk-iuk..." and keeps on moving back and forth few mm.
B. starts running, and takes the RPM you have set, BUT clearly accelerates poorly and has no power to do any machining
Either way, it wont give any errors.

The local dealer say it sound like "chuch servomotor back-switching error", sorry, dont know how to translate it better. We have tried with another pulse-sensor, but no help.

We tested by heating the servo motor board components, trying to find some bad connections, but no help.

Any ideas? How could we tell if the servo motor itself is broken? To my ear it sound like (when it runs but poorly) like electric motor with some brush coal not in function. Not smooth sound, like soft popping in the sound if you know what I mean.

Here is video of the problem. This version of problem is the "iuk-iuk-iuk...." and chuck slightly moves. Sometimes it can go back and forth 10mm or so, this vide some 1mm

https://photos.google.com/share/AF1Q...dqME85c1JPTHFn