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EPD channel measuring cosmics out of Rx board, but blue in QA plots and not showing any MIP peaks

Updated on Mon, 2019-12-16 14:54. Originally created by adams92 on 2019-12-16 13:27.
 At the beginning of Run 20 (December 2019), we noticed that a single EPD tile (West PP3 TT24) was showing no signs of life. In the QA plots, we saw a hole: (e.g. https://online.star.bnl.gov/runPlots/20344008.shift.pdf)

and nothing in the ADC distribution: (e.g. https://online.star.bnl.gov/epd/Signal/20344/20344008.adc_Rg5_West.png)


Note that the ADC distribution (found on https://online.star.bnl.gov/ -> EPD Monitoring -> ADC -> ...) is important to distinguish it from a high pedestal. Using the mapping spreadsheet, Xiaoyu and I found the relevant channel in the Rx board, disconnected the cable from the Rx board, and connected a scope to the channel on the Rx board. We did in fact see cosmics; from Xiaoyu's notes:


Also, by changing Vped
  • Done through daqman
  • $ ssh -A you@rssh.rhic.bnl.gov
  • $ ssh stargw.starp.bnl.gov
  • $ ssh -A -X -t evpops@daqman
  • $ cd /RTS/conf/epd/
  • $ cp EPD_TUFFmap.txt EPD_TUFFmap_(DDMMMYYYY).txt
    • e.g. $ cp EPD_TUFFmap.txt EPD_TUFFmap_12Dec2019.txt
  • $ cp /RTS/conf/epd/MappingPatterns2018/Zeros_02262018.txt  /RTS/conf/epd/EPD_TUFFmap.txt
  • In the EPD GUI, click "PHYSICS" on the top bar, then "PHYSICS" in the upper-left-hand box; wait for the yellow circle in "SC State" to finish its loop and turn green.
  • Once finished, we put the state pack to where we found it:
    • $ cp EPD_TUFFmap_(DDMMMYYYY).txt EPD_TUFFmap.txt
    • In the EPD GUI, click "PHYSICS" on the top bar, then "PHYSICS" in the upper-left-hand box; wait for the yellow circle in "SC State" to finish its loop and turn green.
we were able to see the voltage jump in the scope. This meant that either the connector was bad or something about the QT board (or further downstream) was bad. In order to rule out the connector, we swapped the relevant connector (position "C" on its QT board) with the one above it (position "B" on the same QT board). We then took a pedestal run, then directly edited EPD_TUFF.txt (see above) so all channels had Vped set to 60, and took another pedestal run. Rosi (through Akio) had access to the trigger data, and was able to see a difference in the read-out pedestal between the two runs (the readings corresponded to different channels/tiles, but that is irrelevant). We were therefore able to conclude that the connector (EQ1-0x10-C) was bad. We found a new QT32B connector in the EPD cabinet and replaced it. 
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