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Sat Aug 5 11:04:07 2017, gautam, Update, SUS, MC1 glitches return 
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Wed Aug 9 15:15:47 2017, gautam, Update, SUS, MC1 glitches return
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Thu Aug 10 21:01:43 2017, gautam, Update, SUS, MC1 glitches debugging 
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Fri Aug 11 12:32:46 2017, gautam, Update, SUS, MC1 glitches debugging  
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Fri Aug 11 17:36:47 2017, gautam, Update, SUS, MC1 <--> MC3
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Sat Aug 12 14:09:36 2017, gautam, Update, SUS, Glitches stay on MC1  
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Sat Aug 12 22:35:22 2017, rana, Update, SUS, Glitches stay on MC1
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Sun Aug 13 01:35:09 2017, Koji, Update, SUS, Glitches stay on MC1
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Mon Aug 14 20:01:38 2017, gautam, Update, SUS, Glitches stay on MC1
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Wed Aug 16 19:50:17 2017, gautam, Update, SUS, MC1 <--> MC3 switched back
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Thu Aug 17 11:17:49 2017, gautam, Update, SUS, MC1 <--> MC3 switched back 
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Thu Aug 17 17:33:01 2017, gautam, Update, SUS, MC1 <--> MC3 switched back
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Message ID: 13168
Entry time: Sat Aug 5 11:04:07 2017
Reply to this: 13178
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Author: |
gautam |
Type: |
Update |
Category: |
SUS |
Subject: |
MC1 glitches return |
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See Attachment #1, which is full (2048Hz) data for a 3 minute stretch around when I saw the MC1 glitch. At the time of the glitch, WFS loops were disabled, so the only actuation on MC1 was via the local damping loops. The oscillations in the MC2 channels are the autolocker turning on the MC2 length tickle.
Nikhil and I tried the usual techniques of squishing cables at the satellite box, and also at 1X4/1X5, but the glitching persists. I will try and localize the problem this weekend. This thread details investigations the last time something like this happened. In the past, I was able to fix this kind of glitching by replacing the (high speed) current buffer IC LM6321M. These are present in a two places: Satellite box (for the shadow sensor LED current drive), and on the coil driver boards. I think we can rule out the slow machine ADCs that supply the static PIT and YAW bias voltages to the optic, as that path is low-passed with a 4th order filter @1Hz, while the glitches that show up in the OSEM sensor channels do not appear to be low-passed, as seen in the zoomed in view of the glitch in Attachment #2 (but there is an LM6321 in this path as well). |
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