Per WP 7947 & II 4526, Corey and I replaced the 25p D-sub feed thru noted in the ticket and seen on D1002872 for ASC_REFL_A & B_WFS.
As an observation, the feed thru looks okay, testing TBD; but, both the in-air and in vac cable connections were poor with the in-vac connector a good 3/32" away from seating on the side of the conductors. Both screws in this connector were tight indicating a cross thread condition and they were very rough/tight to unthread. Maybe we need a bit of training to insure our connections are solid and sound.
Action shot of Hugh.
Relevant FRS that triggered this is: https://services.ligo-la.caltech.edu/FRS/show_bug.cgi?id=4526
After the flange swap, no clear improvement, but maybe something changed (that's in a sense worse than no change).
Attached is when ASC-REFL_A and B were illuminated using a flash light. Since one leg of differential output of ASC-REFL_A_DC_SEG4 was dead, we use a gain of 2 for this segment while others are 1.
If the problem was fixed (i.e. both of the differential output legs are functioning), I expect that A SEG4 output is twice as large as everything else. In reality it's somewhat larger than others (100 cts max VS 80) but not as twice as large, I don't think that it's fixed.
If this difference (100 VS 80) is real and is a result of the flange swap, though, this is a problem as it affects the centering. We'll see tomorrow by directing the beam to each segment one by one.
Another thing I noticed is that A SEG4 DC output is much noisier than others when dark (second attachment). The noise was worse before the flange swap and didn't change after, something I didn't pay attention before.