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    User name M. Stevens

    Log entry time 12:03:33 on February 14, 2008

    Entry number 228563

    keyword=Right dipole front panel lights

    The right dipole Dynapower power supply had some inoperative front panel idiot lights, specifically the "M3" light, "remote on", "phase current imbalalance" lights. I replaced the digital output board in the Allen-Bradley slot 6 to fix the "M3" light. As I was troubleshooting the other lights, some more of them failed: the "transformer overtemp" and "thyristor overtemp" lights went out when I replaced the digital output board in slot 3. I read voltages and found what seemed to be ambiguous readings on the various lights that were out. During this process the "discharge load temp" light became inoperative. The board sinks the outputs, but when I read the levels of the various inoperative lights (channels) I saw anything from 2.1V to 0.8V or less, with the output enabled. I became suspicious of the cable at this point, and devised a test which would drive current through the cable. Sure enough, channels one through six would not handle the 20mA of current to light an led. I reterminated the lower end of the cable and all of the lights worked fine. I ordered some optocouplers for the retrograde board.

    A copy of this log entry has been emailed to: folts@jlab.org, fansler@jlab.org, spiegel@jlab.org, segal@jlab.org