After the replacement there was a DC readout lock (Aug 12 4 UTC). The TMSX QPDs look cleaner during this lock, although not quite perfect. The first plot is the spectrum of the TMSX QPD sum at three times - ER7 (blue), Aug 1 (red), and today (green). The second plot is the same for TMSY. It looks like there might still be some excess noise with the same shape but a much smaller amplitude. We'll check this again when there's a nominal lock.

Contrary to what I reported in my previous alog, it is possible to see the 1821 Hz noise in the OSEMs even though they are recorded at 256 Hz. The third plot shows the OSEM RT signal (and SD is the same) at four different times. Blue is the time when Matt and Evan alogged the problem. Red is the lock after the amplifier had been smacked and the audible oscillation was gone. Green is Aug 8 (a week later), and yellow is today. The noise is gone today after the amplifier was replaced.

The confusing thing is that the red trace is the same time as the plot in my alog. It seems that the high frequency noise in the amplifier was not there, but there was still just as much excess noise on the TMSX QPD. That might mean that the decrease in the excess noise today is just coincidental. We'll have to keep monitoring this.

There's a later DC lock today that seems to have a more nominal configuration. The noise in the TMSX QPD is like it was before the amplifier swap, so it hasn't been fixed and must be unrelated to the satellite amplifier problem. The previous lock, where the noise looked smaller, had a factor of ten lower DC level than the current value. The second plot is just a quick check showing that the high frequency line from the satellite amplifier is still gone since the swap.

The S number and S/N for the "old" satellite box for SUS-TMSX_M1_OSEM SD and  RT channels are:

S-number bar code  S1100176

S/N  3202-022

The identifiers for the new box will be obtained at a future oportunistic entry to the EX electronics racks area.