You should see a response on the screen from the blender that looks something like:
01T00BTest String6C
If this works than communications is working. Try starting the blender and then perform the same test. If when the blender is running this test fails, then the problem is noise from within the blender (consult service).
If this test fails and you see scrolling junk on the screen then the problem is that you have noise on the com cable. The cable’s shield should only be connected at the PC end and not at the blender end. When the cables are unhooked there shouldn’t be continuity between the hoods on any of the cables. If there is, fix the problem.
If you’ve fixed the shields and are still seeing noise then start unhooking blenders. If when you unhook a blender the noise goes away, then check the blender (consult service).
If the blenders aren’t causing the noise and you’ve run the cables through conduit (if not then you must), then some external device is creating the noise. Begin shutting electrical devices off one at a time until you find the problem. Sometimes this issue can be caused by weak ground circuits. To resolve a weak grounding grid in the plant you have to drive a copper spike through your floor into earth ground near the source of noise (no other solution).
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