Matt, Evan
Why do the TMSX RT and SD OSEMs have such huge spikes at 1821 Hz and harmonics? These spikes are about 4000 ct pp in the time series. In comparison, the other OSEMs on TMSX are 100 ct pp or less (F1 and LF shown for comparison).
Also attached are the spectra and time series of the corresponding IOP channels.
On a possibly related note: in full lock, the TMSX QPDs see more than 100 times more noise at 10 Hz than the TMSY QPDs do.
From Gabriele's bruco report, the X QPDs have some coherence with DARM around 78 Hz and 80 Hz. A coherence plot is attached.
It seems similar to the problem from log 12465. Recycling AA chassis power fixed the issue at the time.
Quenched the oscillation for now (Vern, Keita)
We were able to clearly hear some kHz-ish sound from the satellite amplifier of TMSX that is connected to SD and RT. Power cycling (i.e. removing the cable powering the BOSEM and connecting it again) didn't fix it despite many trials.
We moved to the driver, power cycled the driver chassis, and it didn't help either.
The tone of the audible oscillation changed when we wiggled the cable on the satellite amp, but that didn't fix it.
Vern gave the DB25 connector on the satellite amp a hard whack in a direction to push the connector further into the box, and that fixed the problem for now.
