I have an older unique Fanuc made CNC light manufacturing Autoprofiler, circa 1989. Using a 3M Model C controller and have all electrical schematics. However if anyone has done trouble shooting on the feed rate control switch circuity to locate a defective component please advise as to sequence.
Problem, feed rate control does not function in a linear fashion, 10% is about the only switch position that works with stability. The feed rate also appears to become non linear when the X-Y vector coincide. This controller has the 15 position switch with four banks of contacts. Diagnostic bit switching is not to schematic and suspect it is past the switch (switch deoxidized) with no noticeable changes. When in the 150% override at 20 ipm the AC servos appear to fight with each other for positioning. You can feel the cogging in the table and hear the cogging. Looking to find a root cause diagnostic procedure, any help will be appreciated.