When I power up the machine, I get this high pitched electronic squeel. It seemed to come from the Z axis motor, but its hard to tell. This is without the spindle or table moving. Partner IV, Centurion IV. What do you think this is? When I e-stop, it goes away.

Seems like you have a drive that needs tuned. When you E-stop your shutting the drives down.

How are the drives tuned.

You won't get rid of the high pitched whine, not without replacing the drives. The drives on the Cent IV are old enouth to have their frequency in the audible range.

Dan

How load is the squeel ? My Centurion IV Partner V has very high pitched
drives compared to my other CNC's. Did this just start happening?
Your drive boards are in the right cabinet if you are facing the machine.
Open the door and take a look, if they aren't labeled I'll have a look at mine and get back to you.
How far have you got along with your machine? Haven't corresponded with
you in a while, so I figured you had things moving along.

It's medium loud, and a pitch that is really anoying. Is the noise caused by the drive motor? Can it be repaired or rebuilt? Is this noise common? I do have the machine running, and I am using it. I had to adjust the gridding stop on the x axis, to allow the machine to grid. Now it will program and run. My computer smoked itself so I do not have a computer connection. What format do I use to write programs on a computer, that I can load into the machine?

Mine drove me crazy when I had it in a 400 sf garage, but it doesn't bother me anymore since I moved it into a bigger shop. It's by far the loudest of
my CNC's. Has the noise gotten worse since you got it or is it just annoying
you?
Start your programs on the computer with a % sign and end them with one.
Did ever score a programming manual? If you haven't, email me at
cobro@reachone.com and I'll send you some sample programms.
These Centurion IV's do not use standard G-code protocols, but
they are very close once you get use to them.

The noise hasn't gotten any louder. I seems like its only comming from the z motor. I did get a manual. Computer is fixed. I can't get it to talk to the mill. I tried Hyperterninal and Direct Connection, nothing.

That squeal is your incentive to get the tool into the cut. :D If you can still hear it when it's cutting, then feed harder, deeper and/or faster :D

Did you hook a null modem connector in the communication cable?
Parameter #86 sets your baudrate in the machine. Mine uses 600 baud
which would be .0232 in parameter 86. Make sure the the machines baud matches the computer.
If you have a program written in the PC, type in MDI at the machine
G55 (enter)
cycle start
This sets the machine up to receive a program from PC. Make sure the first character in your program is a percent sign %.
To download from the machine, set the PC to receive
Then in MDI at the Control
G54 (enter)
Cycle start

Look back at your original post for the machine in this forum and there
will be more information, I recall giving you this information once before.
Search Windows in your PC for a program called Terminal. I kow it
works with your machnie and it supports the older baud rates.