[Chizel]

I have an older Milltronics Partner I. I was running parts for quite a while and after a cycle was about to finish, the "Z" axis started moving erratically up and down. It was enough to set off a servo alarm. I tried to reset and still same thing. I tried to power down and back up. During Home cycle same thing. Does anyone know what is going on with this machine?

[chipsinpan]

You didn't mention how much it moves up/down .
I had a problem with Z that could only be seen when I was indicating a part.
Noticed that Z was "hunting" for a plane and going up/down +/- .015".
I turned out to be accumulated carbon from the motor brushes was bridging across poles on the armature .
Milltronics has a memo on this called " Cleaning tachometers on DC drive motors "
It involves blocking up the head , removing the motor from the top of the column , disassembling the end cap of the motor and removing the brushes , then blowing out the dust .
Not sure if this is really what your problem is though .
Bob