4th Axis Stepper Motor problem

[SiJones]

Hi
We have a 2600 pro with 4th axis fitting.
Recently the stepper motor on the 4th axis has malfunctioned.
Instead of the motor rotating nomally it has started to vibrate back and forth, in an irregular pattern.
This happens during a programme and during manual control.
I have stripped down the 4th axis and there appears to be no problem with the meshing of gears from the motor to the chuck.
With the stepper motor removed from the chuck assembly it still malfunctions.
The wiring on the stepper motor looks good, clean with no wear.
The 4th axis is about 2 years old but has not been used a lot until this year.
The four pin connection to the machine looks good and we are getting a reading off 2 of the pins of around 30 volts the other 2 read 20 volts.
Is there anything unusual about these readings and is there anything else you recommend checking?
Thank you.
Simon

[bradders]

Checking for broken wiring ...................
1. Disconnect the 4th axis cable from the Router 2600
2. Looking carefully down the plug of the trailing lead of the 4th axis, you should see pins and the letters A, B, C etc
3. There are two winding in the stepper motor and they are wired in pairs as follows.........

Pair 1
A+ (Black Wire) PIN A in plug
A- (Orange Wire) PIN B in plug

Pair 2
B+ (Red Wire) PIN D in plug
B- (Yellow Wire) PIN E in plug

With and electrical meter check the continuity / resistance of these 2 circuits, they sould have similar characteristics if the wiring is OK. While testing move the wiring about and see if any anomalies appear

[SiJones]

Brilliant, yellow wire disconnected at pin end.
Now repaired and working.
Thank you very much for the prompt advice.

Simon

[bradders]

Hi Simon, I'm glad the problem was and easy one to fix and you are now back up and running