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User name M. Stevens/S. Spiegel
Log entry time 16:14:18 on May 18, 2007
Entry number 202580
This entry is a followup to: 202070
keyword=Right Q2 remote control repaired
Right Q2 had been operating in local manual control since Monday. It was
believed that one of the optocouplers on the regulator boards were the
problem. We changed those optocouplers, and the discrepancy remained.
While we were working, Scot observed that in local control we could hear
the soft-start and main line contactors operating in local mode, but not
in remote mode, even though the indicator light (ON) was lit in both
modes. He also observed that the lamp was dim in remote mode. We traced
the signal that actuated the main contactors in remote mode, and found
that it was optically isolated on one of the three small opto boards
(designator UA UOG12) on the side of the supply, where the RS-485
interface used to be. (The serial interface was replaced with discrete
commands from the ioc during commissioning.) The three discrete commands
from the ioc are: Main Power ON/OFF, Polarity, and Reset Interlock. We
surmised that the optocoupler was passing enough current to light the
lamp, but not enough to drop the ~100A contactors. We socketed and
replaced the optocouplers on the isolator boards, and everything worked
fine.
A copy of this log entry has been emailed to: folts@jlab.org, gomez@jlab.org, segal@jlab.org, fansler@jlab.org