problem with B-axis

[Pranita Kashyape]

I am having SV3X robot which has 6 axis. When I give B-axis, a particular horizontal position or any position upward to the horizontal. The B-axis falls automatically downward, after reaching to the particular position, instead of remaining steady at the given particular position. Is there any solution to this?
 I think that may be the timing belt may have become loose. Is that so? or something else?
   thank you.

[tony gast]

Does it fall when the program is running or when you cycle power?

[Robodoc]

I have see this before.  If an axis will move down but not up you are usually missing one of the three phases to the motor.  Check both sides of the 2BC connector (the one on the left when you are at the back of the robot) to make sure none of the pins have been pushed in.
If the pins are OK you may have an open wire in the harness or a bad motor.

[Pranita Kashyape]

Yes it falls when the program is running, that is the B-axis reaches to the position given in the program and then starts falling down.
 I checked the 2BC connector, the connection is ok.
 
 Thank you.