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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: 1925     Entry time: Mon Sep 18 00:46:08 2017     In reply to: 1918     Reply to this: 1926
Author: rana 
Type: Summary 
Category: FSS 
Subject: FSS modifications: series resistance (R1 and R2) to monitor points on servo board D040105 

Ugh - no, plugging in the network analyzer should not change the gain of the servo. This seems quite bad. Lets discuss and fix.

In addition to Frank's fixes, Tara also did some patches with advice from Koji. We should make sure you have the right version of schematic.

Quote:

 

I switched the R1 and R2 50 Ω (on D040105-C) out for something higher again, this time 470 Ω.  I could only find 470 Ω in the EE workshop (which is close enough to the design value of 453 Ω).

Now plugging 50 Ω loads into the OUT1 and OUT1 common monitor points lowers the common path OLG by 7.8 dB and 10.8 dB respectively.  This still seems like a big change to me but I'm not sure if I should increase series resistance any higher.

Let me know if this is dumb and I'll change it back.

In any case, once you have R1 and R2 at 450-500 Ohms, the circuit should not change behavior just by adding 50 Ohms onto EXC or OUT2. You should be able to do the TF without OUT1.

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