J. Kissel, J. Warner

Jim unlocked the ISI and we installed damping loops on the H1 HAM6 ISI (such that we could run SUS close-out TFs). The damping loop install went poorly, but eventually we got it to work in an odd configuration. Below is the chronology.

- I installed a copy of HAM4 damping filters using straight copy and paste from foton.
- Tried turning loops on, got immediate trip. Repeated just to be sure, with the same result.
- Checked HAM6 ISI DAMP filters against HAM4 filters in foton, confirmed they're identical
- Checked Basis Transformation matrices, confirmed they're identical to HAM4, and they match T1000388.
- Confirmed with foton that the actuator compensation filters were installed and correct (i.e. they match HAM4).
- Confirmed with foton that the GS13 calibration filters were installed and correct (i.e. they match HAM4).
- Confirmed that all signs along the chain, in the GS13INF, DAMP, and OUTF filters were the same as in HAM4.
- Checked that gain switching on GS13s was functional, and that were were in low gain.
- Tried closing loops again, still unstable.
- Jim installed HAM6 damping filters using the "normal" Matlab quack method from commission scripts that were designed from an old set of plant data.
- Confirmed with foton they installed correctly and showed very little difference between HAM4's filters.
- Tried them, still unstable.
- Noticed that all corner station ISIs had ADC saturations on CDS overview screen. Found it to be STSA (i.e. the one by HAM2) which was railed, and being piped to every ISI and HPI front end.
- Went out to racks, re-zeroed STSA, saturations disappeared, still no change in behavior. Damping loops still unstable.
- Turned down / off purge are in HAM six. Amplitude of GS13 motion went down, but still the loops were unstable.
- Performed the radical -- flipped the sign of loops in the DAMP filter bank, AND IT WORKED.

We can't think of any reason that there would be a sign flip in the chain, but for now, we leave it and move on checking out SUS.