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Entry  Wed Dec 10 15:05:32 2014, Jenne, Update, Electronics, Xend QPD whitening board modified already IMG_1776.JPG
    Reply  Thu Dec 11 16:42:12 2014, Jenne, Update, Electronics, Xend QPD whitening board plan QPDwhiteningModification_11Dec2014.pdf
       Reply  Fri Dec 12 19:54:21 2014, Jenne, Update, Electronics, Xend QPD whitening board modified QPDwhiteningModification_XtransCompleted_12Dec2014.pdfIMG_1779.JPGQPD_Xtrans_Ytrans_12Dec2014.pdfQPD_Xtrans_Ytrans_DarkVsLock_12Dec2014.pdf
          Reply  Sat Dec 13 00:35:11 2014, rana, Update, Electronics, Xend QPD whitening board modified 
          Reply  Mon Dec 15 22:30:50 2014, Jenne, Update, Electronics, Yend QPD modified 
             Reply  Mon Dec 15 22:45:59 2014, Jenne, Update, Electronics, Yend QPD modified QPD_Ytrans_oscillating_15Dec2014.pdfQPD_IOPchannels_Ytrans_oscillating_15Dec2014.pdf
                Reply  Fri Feb 13 14:27:30 2015, ericq, Update, Electronics, Second QPD Whitening Switch enabled 
                   Reply  Fri Feb 13 14:59:13 2015, ericq, Update, Electronics, Second QPD Whitening Switch enabled 
                      Reply  Fri Feb 13 18:56:44 2015, rana, Update, Electronics, Second QPD Whitening Switch enabled 
                         Reply  Thu Feb 19 04:09:21 2015, ericq, Update, Electronics, Second QPD Whitening Switch enabled 
                   Reply  Fri Feb 13 17:07:51 2015, Jenne, Update, Electronics, Second QPD Whitening Switch enabled 
Message ID: 10774     Entry time: Wed Dec 10 15:05:32 2014     Reply to this: 10782
Author: Jenne 
Type: Update 
Category: Electronics 
Subject: Xend QPD whitening board modified already 

In April, Koji logged that he had made some changes to the Yend QPD whitening board (elog 9854).  Today, I pulled the Xend board to see if it had the same modifications.  The filter shapes all seem to be the same (as in, the capacitors at the output filters were removed, etc.), and the final gain is the same.  I just realized that I didn't explicitly check if the whitening switches were pulled to ground to permanently turn on the whitenening, but hopefully I'll be able to see that in the photo. 

I have not made any changes today (yet) to the board, so the overall gain is still accessible via EPICS.  I wanted to do a quick check that we won't be saturating things at full power with the maximum gain, before I make a change.

IMG_1776.JPG

EDIT:  After comparing the photos here and in elog 9854, the X end board has the filter shape modifications that were done some time ago, but the whitening is not permanently enabled.  For the Yend board, Koji added a jumper wire connecting (for example) R97 and R106 to the grounded side of C69.  This jumper wire is not in place on the X qpd board.

Before I re-pull the board and modify it, I want to make sure I know what I'm going to do for the gain slider override.

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