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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