Related alog: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=81320

Sometime ago (July/09/2024) the analog DC gain of H1:ASC-AS_B_DC was set from "High" to "Low" when I was looking to extract more information from WFSs about the power coming past the Fast Shutter when the shutter bounces down after high power lock losses. Since this is not necessary any more (see plots in alog 81130) and since keeping this means that we have to either adjust dark offset once in a while and/or making the "shutter closed" threshold for Fast Shutter test (alog 81320), I set the gain switch back to "HIGH", and disabled the +20dB digital gain in H1:ASC-AS_B_DC_SEG[1234] FM4.

Interestingly, when I flipped the gain switch, SEG3 output didn't change (1st attachment). It could be that the specific DC channel is stuck to HIGH or LOW, but it could be that the analog offset happens to be really small for that channel. I cannot test it right now as we're leaving IMC unlocked. As soon as the light comes back I will go to the floor and test.

The second attachment is the relevant MEDM screen (that shows the state it should be in now) and the third one is the picture of the interface chassis (the switch I flipped is circled in red, and it's supposed to be HIGH now).