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Entry  Thu Nov 11 04:32:53 2010, yuta, Summary, CDS, found poor contact of DAC cable, previous A2L results were wrong 
    Reply  Thu Nov 11 11:51:30 2010, Koji, Summary, CDS, found poor contact of DAC cable, previous A2L results were wrong 
       Reply  Thu Nov 11 23:35:23 2010, Koji, Summary, CDS, found poor contact of DAC cable, previous A2L results were wrong IMG_3698.jpgbad-boys.pngIMG_3705.jpgIMG_3706.jpg
Message ID: 3891     Entry time: Thu Nov 11 04:32:53 2010     Reply to this: 3895
Author: yuta 
Type: Summary 
Category: CDS 
Subject: found poor contact of DAC cable, previous A2L results were wrong 

(Koji, Jenne, Yuta)

We found one of DAC cables had a poor contact.
That probably caused our too much "tilt" of the beam into MC.

Story:
  From the previous A2L measurement and MC aligning, we found that the beam is somehow vertically "tilted" so much.
  We started to check the table leveling and the beam height and they looked reasonable.
  So, we proceeded to check coil balancings using optical levers.
  During the setup of optical levers, I noticed that VMon for MC1_ULCOIL was always showing -0.004 even if I put excitation to coils.
  It was because one of the DAC cables(labeled CAB_1Y4_88) had a poor contact.
  If I push it really hard, it is ok. But maybe we'd better replace the cable.

What caused a poor connection?:
  I don't know.
  A month ago, we checked that they are connected, but things change.

How to prevent it:
  I made a python script that automatically checks if 4 coils are connected or not using C1:IOO_LOCKIN oscillator.
  It is /cvs/cds/caltech/users/yuta/scripts/coilchecker.py.
  It turns off all 3 coils except for the one looking at, and see the difference between oscillation is on and off.
  The difference can be seen by demodulating SUSPOS signal by oscillating frequency.
  If I intentionally unplug CAB_1Y4_88, the result output for MC1 will be;

==RESULTS== (GPS:973512733)
MC1_ULCOIL      0.923853382664 [!]
MC1_URCOIL      38.9361304794
MC1_LRCOIL      55.4927575177
MC1_LLCOIL      45.3428533919


Plan:
 - Make sure the cable connection and do A2L and MC alignment again
 - Even if the cables are ok, it is better to do coil balancings. See the next elog.

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