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Entry  Fri Apr 10 03:44:51 2015, Jenne, Update, LSC, Some small progress, may have DAC problem? PRMI_sb_powers_9Apr2015.png
    Reply  Fri Apr 10 12:09:19 2015, ericq, Update, LSC, Some small progress, may have DAC problem? 
    Reply  Wed Apr 15 21:00:56 2015, Jenne, Update, LSC, DAC fine 
Message ID: 11213     Entry time: Fri Apr 10 12:09:19 2015     In reply to: 11212
Author: ericq 
Type: Update 
Category: LSC 
Subject: Some small progress, may have DAC problem? 
Quote:

At the very end, the last 10 seconds or so, the POP110 power goes down, and sits at about half it's maximum value.  POP22 isn't quite as bad, in that it still touches the max, but the RIN is about 50%.  The carrier DC signals (TRX, TRY, POPDC) don't see this huge jump.  I don't think I was touching anything the last few tens of seconds.  I'm not sure yet how I can so significantly lose sideband power, without losing a similar amount of carrier power. 

I saw this same kind of behavior in my locklosses on Wednesday night; we should check out the 165 data, and see if the 3f PRCL error signal shows some drift away from zero.

Also, it's odd that CARM_IN1 and REFL11_I_ERR have different low frequency behavior in the plot you posted. I guess they have some difference in demodulation phase.  REFL11_I's bump at -40sec coincides with the dip in arm power and a rise in REFLDC, but ASDC seems pretty smooth, so maybe it is a real CARM fluctuation.

I set the REFL11 analog demodulation angle (via cable length) about a year ago (ELOG 9850), with some assumption about PRCL having the same demod angle as CARM, but this was probably set with the arms misaligned. We should recheck this; maybe we're coupling some other junk into CARM. 

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