J. Kissel, A. Pele, T. Sadecki, B. Weaver,

After another day's worth of fumbling and hand-waving, we've finally traced the discrepant transfer function magnitude to a loose cable connection at the air-side of the feedthrough. In the course of attempted fixes, we measured a few more things, moved a few more things, replaced the R0 F2 and F3 OSEMs, but the only thing that fixed it was the cable connection. This flaw with the electronics chain should have been found earlier with our cable swap on Friday, with remeasuring the open light current, and with Arnaud's DC actuation test below, but frustratingly, it did not. But we found it. 

I'm in the process of getting formal transfer function measurements now, but I'm confident from what I'm seeing thus far that this SUS is read for close-out. Will post comparison TFs once they're finished.
We have exORSIIIIIIIZED the demons. This SUS is clee-uh.

Details (In rough chronological order)
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- Arnaud compared the ETMY and ITMX R0 F2 to F2 and F3 to F3 drive at DC using the alignment offsets (the only QUADs available, so take ERM and TCP chain comparison with a grain of salt), and concluded that the chains are driving with comparable and within a chain F2 and F3 are of comparable strength with such a quick study. 
- Betsy retook an L2L transfer function (just for sanity's), saw the same discrepant factor of two -- and some more Yaw resonant cross-coupling. Still F2 shows the majority of the badness.
- Decided just to swap the OSEMs, and hopefully move on. Below are the new serial numbers, open light current, and compensation gains and offsets. These *have* been installed. We'll take a new safe.snap this evening after all the commotion has died down.
- Betsy & Travis poked at this, looked at that, iterated with measurements several times on the floor.
- At last, Betsy went a long the signal chain, and made sure all connections were secure, and finally found this bad connection at the in-air connection at the feedthrough.
- Simultaneously, Travis loosened up the the cable loop from the optical table to the top mass. This may have alleviated the extra Yaw peaks that had shown up today. 

Open light current values and serial numbers for the new OSEMs.
      Raw    New     New        S/N
      ADC    Gain    Offset      
R0F2 25646   1.170   -12823     077
R0F3 26554   1.130   -13277     147

We'll also update the OSEM chart and grab a new safe.snap once transfer functions are finished.