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User name Jack
Log entry time 00:00:04 on April 29, 2009
Entry number 269567
This entry is a followup to: 269527
keyword=VDC trip hold circuit not functioning correctly
When I got into the Right Shield House I found the A channel ON and the B
channel OFF, on the Bertan supply. The A channel voltage readback had a
varying picket fence structure in EPICS. I disconnected the HV cables
from the VDCs and used a resistive load to observe the HV. The A channel
would reset after a trip, with somewhat varying delays. The behavior
moved to the B channel when I moved the reset cable from the A channel to
the B channel. The original B channel configuration seemed to behave
correctly. I swapped out the Bertan, just to be sure. The behavior was
the same. I left the replacement Bertan installed and put the supply we
had been using on the Radcon shelf. On the VMIC 2210 relay card, I
swapped the 8 top relays of the lower set of 32 with the 8 top relays of
the upper set of 32. We are not using the upper set. The variable delay
of the auto-resetting made me think the contacts in the relay used to
reset the supply might be going bad. After swapping the relays things
seemed to work correctly. The A channel is the one used for the top VDC,
which gives some more understanding of the burn through on the foils.
This also pointed out a couple of problems with the EPICS control of the
Bertan supplies. The reset is essentially done by putting the supply in
auto-reset for 3 or 5 seconds. During that time the supply will reset if
it trips. It will not reset after the relay closes after the 3 or 5
seconds. But, that short bit of time it is able to reset automatically is
not something I had considered. If the supply trips off it does not seem
possible to set the demand voltage to zero or something else. In fact it
seemed to wander a lot until the VDC was reset. This needs to be looked
at in more depth.