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Entry  Thu Sep 5 19:32:02 2019, anchal, DailyProgress, PMC, North PMC might be cause of 500Hz bump BN_NPMCErr_CrossSpec.pdf
    Reply  Mon Sep 9 16:31:34 2019, anchal, DailyProgress, PMC, North PMC open loop investigation NPMC_openInvestifation.pdf
       Reply  Tue Sep 10 17:13:51 2019, anchal, DailyProgress, PMC, North PMC Servo Card Upgraded 
Message ID: 2421     Entry time: Tue Sep 10 17:13:51 2019     In reply to: 2420
Author: anchal 
Type: DailyProgress 
Category: PMC 
Subject: North PMC Servo Card Upgraded 

It turns out that the noise is either injected through the EOMs or through some mechanical oscillation in the table or through RFPD SN020. The servo card was working normally. However, since I had opened up the box, I used this opportunity to increase the first stage gain on the FP2test input and also made it 50-ohm input impedance by adding a 51 Ohm resistor in parallel to R8. Now, beware that on the actual board, R5 and R8 labels are actually swapped. This helped keep the gain set by AD602 to 7 dB now, instead of 30 dB maximum. This way we are able to increase the gain more instead of getting saturated. The hunt for 500 Hz bump would move to finding on table sources now.

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