Fanuc 424 alarm

[DALEK]

Hello, I am in despair. I thought I was clever and could fix anything but obviously I am not.
I have a goodway lathe with Fanuc OT control. When the machine is first turned on, the z axis can only be moved about 5mm in each direction, then after about 1min alarm 424 comes on, which is a servo error, although no error code appears on the servo amplifier.
I thought the axis was mechanically stuck so I removed the motor but the same thing happens. the motor spindle will only travel about 1/3 rd turn in each direction. also there is a whistling noise coming from the motor, the more I try to turn it the louder it gets.
The motor turns easily by hand.
On the diagnostics page I get 00100000 which is ovc error.The motor and wiring seem Ok and I have recieved the servo amplifier back from testing with no fault found.
Can anyone help me please?

[Al_The_Man]

What servo's are fitted AC red cap or DC yellow cap?
If DC, do you know the feedback method, encoder or resolver?
Al.

[samu]

i'm not an expert but are you sure that one phase is not missing?

[DALEK]

Thanks for replying. The motos are red cap A06b-0127-b077.
I am at my wits end.

[DALEK]

My thought also was that there may be a phase missing but I have treble checked and meggered the wiring to the motor and the motor windings.

[Al_The_Man]

If AC servo's it sounds very much to me like an encoder commutation issue.
Are the motors the same size where you can swap them to try?
Al.

[DALEK]

One of the machine operators just came into my office and asked why I was taking technical advice from a baby smoking a cigarette and a squirrel. I could not think of a witty answer because I am losing sleep over this machine.
The motors appear to be the same size but the other one seems to have a gearbox on. I could change the motors over but I reckon This to be a good half a days work at least. Is there any way I could interchange them electrically, or is that to complex?

[Al_The_Man]

You should be able to swap them at the drives, depending on the models you have.
Early type have the Grey 20p Honda connector on the drive.
There were quite a few types of drives fitted to the 0.
If you have the manual, referring to them may help with the position of the cables.
You just need to swap the encoder/commutation feedback plug and the three stator conductors.
There is also a temperature sensor in the motor windings that come out through the encoder socket, but I think if that was open, you would get a fault right-away.
Al.

[Dan Fritz]

Maybe because that baby smoking a cigarette and that squirrel are some of the smartest guys around. Listen and learn ...

[DALEK]

Thanks for your replies guys, this is a small shop and it makes me feel like I am not alone with this problem.
I have manuals for the machine and the cnc but neither cover the drive.
The motor drive wires are easy to figure out. The others are more difficult. It is an alpha drive with 9 off 20 pin sockets, of which only three are used. In the second socket is cable JX1A. In the fourth is PWM11-JV1B, and the fifth is PWM12-JV2B. I would guess that the latter two are the encoder inputs. I dont want to guess as I am worried I may do more damage. Can someone confirm this, otherwise I will do it the hard way and swap motors.
Sorry to ask so many questions.

[Al_The_Man]

Here is an Alpha drive manual that may help find them, it looks like JV1B etc.
http://www.divshare.com/download/5979983-6d3
Al.

[DALEK]

Thanks again guys.
You may find this difficult to believe. I have swapped the motor power wires and swapped the encoder inputs to the servo amplifier. You would think this would make the x axis the y axis and vice-versa. But no! The machine operates in an identical fashion. The z axis is still the z axis and the y axis is still the y axis. Everything is exactly the same, including the alarm. I am beginning to think the machine is a victim of demonic posession. If I dont hear a better idea I will swap motors.