After the LHO IFO dropped lock around 1pm, Leo and I jumped on making more charge measurements of ETMx and ETMy via the oplev/ESDs. However, we immediately recreated that there seemed to be no coherence in the ETMy measurements. We fumbled around for a while looking at no coherence with signals here and there and then invoked Kissel. Sure'nuf, the ESD drive on ETMy wasn't driving in "LO" or "HI" voltage mode. Richard headed to end Y and re-discovered that turning things off and reterminating the DAC cable fixed the problem - see alog 13335 "Lock up of the DAC channels".
The ETMy measurements are now in progress. Again.
Meanwhile, we attempted to look at why the ETMx LL ESD drive wasn't working and confirmed what Keita saw last night - it doesn't work. We see the requested drive in the monitor channels which means that the signal goes bad somewhere beyond the chassis (toward the chamber). As usual, "no one has been down there" but we're not sure how we can use this ESD to lock the IFO with a dead channel. Richard reports that he will go there tomorrow to investigate.
In case anyone ISN'T tired of hearing that the ETMx OL isn't healthy, here's a snapshot of ugly glitching in the YAW readback. (Jason has stated numerous times that he plans to swap this laser when we give him time to do it.) Just recording again here since we have to stare at it for ESD charge measurements. Ick.