We seemed to have some strange PSL and IMC problems today, and we were suspicious about this TTFSS swap that occurred a few days back to notch the 2.5 MHz peak.
We had to increase the COMMON GAIN to compensate this change.
 
We measured the IMC OLG, FSS OLG, and FSS TEST1 spectra and everything seems normal.

The FSS OLG is around 350 kHz.  Remember that the FSS OLG crosses unity at -10 dB due to the nature of the TTFSS box TEST1/TEST2 points.
The IMC OLG is around 56 kHz.  56 kHz is around equal to 3 * FSR / 2, so there's a dip there associated with the CARM feedback coming from the 9 MHz resonating in the arms.
The TEST1 spectra should be compared to those in alog 65258.  
I compared to one of the old TTFSS spectra measurements, the noise seems lower now than it used to be (PDF 4).

Overall, the PSL seems healthy, no obvious problems.


alogs:
team PSL swaps the TTFSS alog 66839
we reverted set the common and fast gains lower to avoid power glitches alog 65675
previous PSL measurements with old TTFSS alog 65258