I checked the 1700 card I have and the 1800 is probabally the same, I suspect you may have inadvertantly blown the X Diff. reciever, unfortunately it appears the Differential recievers for the encoders are SMT type MC3486's which makes it tricky to replace, The IC's themselves are cheap but unless you are handy with a tiny soldering iron or knows someone that can replace SMT IC's it may be the best bet.
The IC's are located next to the 100 pin connector and can be identified by placing your ohmeter on the ICM2900 on one of the X inputs and find a pin on one of the MC3486's that has zero ohms continuity.
I believe you said you had a 2 axis card, If you only want to use one axis then just address the Y axis only, The Galil card always sees the encoders in a certain order but you should be able to label the Y axis to X in the Camsoft s/w.
Al
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.