First, you can't alway trust the axis specified by the error message.
DAC overflow means the controller card (BMDC) put out a max command voltage (10 volts) to the drive card to move the motor and the motor did not move. Or maybe it did and the endoder did not indicate any change. Could be a bad drive card, motor, encoder, or cable.
In manual mode does the DRO work ? Test by turning the handles. If no count, on one axis, encoder/cable may be bad. If both axes don't count, encoder power supply is out.
When the display says 'power on', if you try to turn the axis handle, does it move; it should not, the control should try to hold position. Try this on both axis.
If both freewheel, it may be a bad drive power supply. If power supply is ok, the drive cards may not be 'enabling' when commanded. This may be a bad BMDC card.
If one axis is free wheeling you can switch motors between axis to see if problem follows the motor or stays with the axis.
Since the cables are not long enough to switch between motors: take off one motor and place it on the floor and swap cables between motors at the motor. Both motor power and encoder cables.
Try a 'drive-on'. If the failure stays with the axis, it is a drive card or cable. If it follows the motor, its the motor.
Swap X & Y drive cards. Do a 'drive on' if problem follows the card, this is the problem.
Note:
1) Be sure to shut down main power when moving parts around.
2) Before main AC power-on, move table to center of travel in X & Y, and push in E-Stop.
3) Power up machine. When ready to do 'drive-on', release E-Stop but be ready for possible run-away. If machine runs-away push E-Stop in immediately.
Check out this site for more info and for parts.
http://www.emi-inc.net/bridgeport/index.html
