Alexa, Sheila, Kiwamu, Evan
Tonight we hoped to proceed further with the full locking procedure.
Unforunately, we have been stymied by repeated MC1/MC3 trips described in LHO#16128, and frequent unlocking of the modecleaner.
Eventually we noticed that some of these unlocking events were correlated with our attempts to lock ALS COMM. Sheila went out to check the IMC PDH loop, but found it is healthy, with a 28 kHz UGF with 40 degrees of phase.
Next, we noticed that even when the IMC stayed locked, ALS COMM would not lock. Sheila went out into the LVEA to check the health of COMM, and found that the PLL was not even locking (despite the digital system reporting that it was locked). Eventually, we shifted over the COMM signals from the COMM PFD to the DIFF PFD, and we were able to get COMM locked. We thought this meant that the COMM PFD was broken, but when we plugged the COMM signals back into the COMM PFD, we could get COMM to lock as well. Loose connection? Badly crimped cable? Unclear.
The following UTC times give some MC1/MC3 trips:
- 2015-01-16 22:24:00
- 2015-01-17 04:33:00
- 2015-01-17 04:46:00
We also caused HAM2 HEPI to trip several times. I had to adjust PR3 alignment to get the COMM and DIFF beatnotes back to a nominal value. These new alignment positions have not been saved yet.