You need to get yourself a 10 Maintenance manual, F14 is the 5amp 24v dc supply for the connection I/O unit, so basically you have a short on one of the external inputs or outputs, you need the machine prints and using a meter on the ohms scale connected across the 24v on the card measure for low resistance, then if the board has multiple I/O plugs and sockets, remove them one at a time and see which has the short when the meter goes to higher resistance, you will then have to test each of the likely circuits in turn for a short.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.