Reports until 09:36, Tuesday 19 July 2016
H1 PSL
peter.king@LIGO.ORG - posted 09:36, Tuesday 19 July 2016 (28487)
ISS AOM Driver
After restoring the AOM driver back to its original power cable, the ISS would not lock and kept oscillating.
The servo control voltage kept varying between ~0.2V and ~0.6V, meaning that the amount of diffracted light
requested was varying from one extreme to another.  I looked at the diffracted spot and all I noticed was the
intensity of the diffracted order seemed fairly constant.

    The input RF was measured with an oscilloscope to be ~410 mVrms, which as I recall is not enough.  I opened
up the AOM driver and the +15V voltage regulator was no longer supplying 15V.

    The spare AOM driver has been installed for the time being.

    Whilst hardware-wise things are in place, I will have to wait until the computer maintenance tasks are
completed before being able to test the ISS again.

    The external laser shutter - ie the one located in the high power oscillator - is closed for now, and
the watchdogs have been turned off.