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Entry  Fri Sep 8 00:32:20 2017, awade, Summary, FSS, Schematic block diagram FSS loops CTN_FSS_south_blockdiagram.pdf
    Reply  Thu Sep 14 21:54:26 2017, awade, Summary, FSS, FSS modifications: series resistance (R1 and R2) to monitor points on servo board D040105 
       Reply  Mon Sep 18 00:46:08 2017, rana, Summary, FSS, FSS modifications: series resistance (R1 and R2) to monitor points on servo board D040105 
          Reply  Mon Sep 18 13:34:13 2017, awade, Summary, FSS, FSS modifications: series resistance (R1 and R2) to monitor points on servo board D040105 
             Reply  Tue Oct 10 00:49:34 2017, awade, Craig, Summary, FSS, Replacing U3 on north path (2010:005) FSS servo board. 20171009_220549_Ser6_ComPathTP1toTP5_09-10-2017_175407.pdffmoenfipkniealnd.png20171009_DebuggingNorthPathServoBoard.tar.gz
    Reply  Mon Oct 2 12:30:15 2017, rana, Summary, FSS, LISO & mfil 
       Reply  Wed Oct 18 11:19:15 2017, awade, Summary, FSS, Comparing south TF to LISO model TTFSS_schematics_awades_hand_notes.pdf001.pdf20171017_South_FSSTFs.tar.gz
          Reply  Wed Oct 18 15:42:59 2017, awade, Summary, FSS, Comparing south TF to LISO model 
             Reply  Mon Oct 23 15:05:44 2017, awade, Summary, FSS, Comparing south TF to LISO model Ser7_South_MainBoard_compiledTF.pdfSer5_North_MainBoard_compiledTF.pdf2017-10-20_18.04.18.jpg
                Reply  Wed Oct 25 23:15:51 2017, awade, Craig, Summary, FSS, Comparing south and north TF to LISO model South_MainBoard_EXC-30dBm_compiledTF.pdfNorth_MainBoard_EXC-30dBm_compiledTF.pdfFSS_all.tar.gz
Message ID: 1954     Entry time: Mon Oct 23 15:05:44 2017     In reply to: 1953     Reply to this: 1958
Author: awade 
Type: Summary 
Category: FSS 
Subject: Comparing south TF to LISO model 

Yes, saturation was the issue.

I turned down the input excitation to -23 dBm and checked with test clips all the way through the the test points on both paths.  Looking with the oscilloscope The only point saturating was TP13, the last stage of the EOM path.  For this data point I turned the power down to -50 dBm; I have a feeling this is too low and maybe we need to injected an excitation at at the start of the EOM to get a decent TF.

I've attached TF for both north and south field boxes. 

South box (2009:007):

There is still a little saturation on stage 3 of the PZT path, it seemed fine looking with the oscilloscope so I'm not sure what is going on there: its possible I was looking with a 100 kHz excitation and that it looked ok, but was not at lower frequencies.  Something to check again. It also looks like EOM stage 2 is saturating.  On the third stage EOM, I turned the excitation right down (as mentioned above).  This looks not right, but might need more excitation closer to that point in the circuit. 

North path (2009:005):

As you can see, there is a fault at the first stage of the common path.  Craig has since diagnosed this to be a fault with the common path circuit.  The pad has peeled off for R4 on the pin2 side of the op amp. Craig has more detailed pictures of his before and after fix of this. Some time in the past R4 had been removed from both of the FSS boxes in the PSL lab and replaced with with a regular metal film through hole resistor pictured below. The resistor sits in vertical pin holes soldered to the pads. I guess the motivation was to have some programmable gain, but the resistors has been knocked and now we have some damage on the north (2009:005 unit).

---

All data and plots are committed into ctn_labdata repo in /data/20171020_Ser7_South_FSSTFs and /data/20171020_Ser5_North_FSSTFs

​Plotting notebooks are commited into ctn_noisebudget repo under /TTFSS_lisomodel

 

Quote:

probably saturating in the PZT path. Repeat with -10 dBm source and look at outputs with a scope to check if its internally saturating.

 

Attachment 1: Ser7_South_MainBoard_compiledTF.pdf  1.196 MB  | Hide | Hide all
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Attachment 2: Ser5_North_MainBoard_compiledTF.pdf  1.294 MB  | Hide | Hide all
Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf Ser5_North_MainBoard_compiledTF.pdf
Attachment 3: 2017-10-20_18.04.18.jpg  1.954 MB  | Hide | Hide all
2017-10-20_18.04.18.jpg
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