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Service Guide ML393/ML393CPlus
Chapter 4 Failure Analysis
4.8.04 Serial Interface - Loopback Test
NOTE:
In order to run this test, a serial loopback test connector must be attached to the printers serial port.
Procedure
1. Place the printer in the Serial Diagnostic Mode
Set the DIAGNOSTIC TEST menu item to YES.
2. Power OFF the printer.
3. Attach the loopback test connector to the printers serial port.
4. Install continuous feed paper.
5. Power ON the printer.
6. The message LOOP TEST prints.
7. The size of the Message Buffer prints.
8. One of the messages listed below prints.
If the message OK prints, the serial interface function has been tested and no problems were found.
If the message IF BAD prints, the signal logic was tested and a problem was found.
9. Hexadecimal characters 20 through 7F are transmitted through the transmit data line.
10. The receive data line receives the characters.
11. The message buffer stores the characters.
12. The data prints.
13. The test runs until the SELECT switch is pressed or the printer is powered OFF.
14. To exit test mode, power OFF the printer.
15. Press FORM FEED while powering ON the printer to enter Menu Mode.
16. Set the Diagnostic Test menu item to NO.
17. Power OFF the printer.
18. Remove the loopback test connector.
Serial Loopback Plug Diagram
