MichaelR, RickS, VolkerQ

After realigning the auxiliary beam hitting IO_AB_PD1 on the PSL table we found that there was a strong 800 kHz amplitude modulation on the light transmitted through the PMC. It was a strong modulation with about 20% of the total power oscillating with a nice ~800kHz sinewave.  The ISS was not happy and would not stay locked.

Fix: Switch noise-eater off and on. This resolved the AM issue.

But even after that the ISS would not engage.  The voltage on ISS PD A and PD B was ~ 6V and we increased it to 10V. This made the autolock

work again, but IO_AB_PD1 again showed a strong AM modulation. This time at ~80 kHz.  We reduced the gain of the ISS from 9.2dB to 8dB and now the ISS appears to be happy again.  No obvious oscillations on  IO_AB_PD1 are observable.