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User name Jack
Log entry time 19:35:10 on June 30, 2007
Entry number 207106
keyword=tech - Q3 work earlier in the day
Ed and I looked at the Q3 power supply. We tried many variations, but I
will give a summary as best I can. The supply generally would not ramp
up. There would be no fault indications, it would just not ramp in either
local or remote. The couple of times it did ramp in local it would get to
a few hundred amps, the Cooling Water LED would light and the magnet
would ramp down. I may have seen the current limit LED flash, but I'm
thinking it was just my eye moving that made it seem so. The Cooling
Water LED would remain on till we cycled power. Scot thought we might be
missing a phase, but as far as we could tell the phases were there. While
looking at things I noticed some high resistance readings on the K8B
relay on the SE20 board. I swapped the SE20 board with the SE20 from Q2
which did not have high resistances on the K8B relay. This also generated
the Cooling Water LED on the Q3 power supply. The Cooling Water LED is
activated by the OK4 optocoupler on the TMRE10 board, if I read the
schematics correctly. That optocoupler is activated by an open loop opamp
that has 0V and the UMON at its inputs. I swapped out the optocoupler,
but the supply still did not ramp up. When we left the supply it was not
ramping up and had no fault lights on.
A copy of this log entry has been emailed to: fansler@jlab.org