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Use the spare green plug in the signal converter if available. Wires going to the display should be removed at this time and set aside. This test can be performed on J4 or J5 (only one jack at a time).Step 2: Setup the Loopback Test on the Phoenix Terminal Blocks. Follow: No communication between computer and signal converter, Failed serial port, DD2006911.Follow: Galaxy, No serial communication, Prolific or Moxa adapter/port locked up, DD2112087.Depending on which one is found follow one of the articles below. If test passes - a loopback test would need to be run on the serial output of the computer or may require the serial adapter be replaced.If the test still passes there is an issue with the test and should be preformed again
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Remove the loopback jumper and run the test. If test pass be sure to test for fail.