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.

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. |