On Tuesday, Dave and I drove to EX to restart the seismic computer and most of the rack components to see if we could get the .085 hz feature that RichM found in December. Sadly, turning on then off again hasn't fixed the problem. I have been able to narrow down the source, I think. In the asds we took before, the feature seemed biggest in the RX/RY loops, so I started by turning those off. This made the feature go away in the X/Y dofs ( or maybe it just got smaller than the background?), it also made the peak disappear in all sensors other that the T240s. I think this shows that the peak is coming from something in the Z1/2/3 (local) T240 signal chain. To dig in a little further I collected an hours worth data with the ISI in this configuration ( ST2 damping only, ST1 RX/RY/Z isolation loops off, X/Y ISI sensor correction off, HEPI Z sensor correction off) and looked at the coherent subtraction between the 3 local Z T240 signals, as shown in the attached figure. The first plot shows the asds of the 3 local channels, Z1 & Z2 are similar at .085hz, but Z3 has a small bump. The second plot shows the result coherently subtracting each of the channels from one another. The fact that the .085hz goes away for subtractions that don't include Z3 makes me thing that there is something going on with the corner 3 sensor. I don't have time tonight to see if this extends to the horizontal dofs on that corner, but I think I want to try power cycling the T240 chassis again at EX.