aLIGO LHO Logbook

H2 General

betsy.weaver@LIGO.ORG - posted 15:39, Monday 11 October 2010 - last comment - 09:12, Monday 18 October 2010(203)

QUAD Test Stand

After returning the sat boxes to the rack, M0 F1 was glitchy.  Filiberto reseated the cable at the Sat box which appeared to fix it.  Now hours later, we are aligning the BOSEMs and have found that this signal peggs at ~6k alot.  We have been able to fix it by reseating the cable at the sat box, but this is not working right...

Comments related to this report

betsy.weaver@LIGO.ORG - 10:31, Tuesday 12 October 2010 (204)

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M0 F1 still a problem this morning.  Filiberto thinks that the Sat box looks like an OP amp blew again - he's pulling the box again for a trip to the ER, er I mean EE.

betsy.weaver@LIGO.ORG - 16:18, Tuesday 12 October 2010 (205)

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Filiberto returned the sat box after another Op Amp swap, but a few hours later we now see bad BOSEM signals in this module...

betsy.weaver@LIGO.ORG - 11:30, Wednesday 13 October 2010 (206)

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Day 5:  Still working on diagnosis of crazy signals from the Sat box 1 (M0 F1, F2, F3, L).
With Filiberto, performed another round of boots to the AA chassis, and bscteststand computer.  No changes so far.  Likely another blown op amp on Sat box 1.

Since we seemed to have changed both satellite boxes and a set of cables (put the new Jay cables in), we might have possibly had more than one problem to diagnose.  We decided to put back in the old cables on a different sat. box and things looked pretty good.  Filiberto is going to fix the blown op amp on the Sat box 1.

betsy.weaver@LIGO.ORG - 15:07, Wednesday 13 October 2010 (208)

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After rearranging sat boxes, Richard and Filiberto found 2 that seem to work.  They hauled away those that have issues.  
With the working sets, I finished aligning all 6 M0 Top BOSEMs.  I just have to finish setting them to 50% OLV and then we can start FFTs.

betsy.weaver@LIGO.ORG - 09:12, Monday 18 October 2010 (214)

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Betsy,

Here is a summary of the troubleshooting of the Sat units.

Oct 8, 2010
Uninstalled two Satellite units SN320073 and SN320078 from test stand.
SN320078 had two bad channels. CH1 had gain off by ~6dB. Replaced IC103 (OP2177AR) with OP284. Did not have OP2177AR replacement part but has been placed on order (expected arrival date 10-14-2010). CH3 had output railing high, replaced IC303 with OP284.

SN320073 had CH4 output railing high. replaced IC403 and IC404 with OP284.
Ran test on units per Test Plan T080062 - UK Satellite Amplifier Pre-Preduction Test Plan for transfer functions and voltage readings.

Oct 11, 2010
Reinstalled SN320073 and SN320078 in test stand. Took opportunity to test unit SN3200715. Tested unit per Test Plan T080062 - UK Satellite Amplifier Pre-Production Test Plan. All test results within specs. Reinstalled unit back in test stand.

Oct 12, 2010
While connecting OSEM's Betsy and company found MO F1 signal to be glitchy. This corresponds to unit SN320078 CH1. While trouble shooting, switched cables with another sat unit. When reconnecting cables to original sat unit, CH1 not responding, output ~2.3V.
Uninstalled SAT unit SN320078 and placed a working unit in its placed. Replaced the "new" cable and installed an older cable on the vacuum side. Connected all four OSEM's and saw a response from all four channels. Disconnected SAT unit and left all four OSEMS connected.

Replaced IC103 with OP284. This IC was one that had been previously replaced. Ran transfer functions on CH1 per Test Procedure T080062. Unit tested good.
Used spare cable and OSEM SN0011 from Betsy to test connecting and disconnecting osems while sat powered on. Trying to see if the act of plugging and unplugging the OSEM could be causing opamps to go bad.

Oct 13, 2010
Reconnected unit SN320078, knowing that all four OSEMs were connected, we expected to see all four channels come up. Upon powering unit up, all four channels seemed glitchy until CH3 died. All other channels then settled to a good state.

Unit SN320073 also had CH4 fail again.

Oct 14, 2010
Replaced IC103 (CH1) and IC303 (CH3) on unit SN320078 with OP2177.
Replaced IC402 and IC404 on CH4 with OP2177.
All opamps that were continually going bad were the OP284. Since they were being used as substitutes until OP2177 arrived.

Oct 15, 2010
Took readings of OSEMs.

SN # Our Readings Stuart's Reading Symptoms
SN688 55.44 57.6 Working Unit
SN695 61.08 62.67 Glitchy - Case causing short
SN674 48.99 49.51 Low Count
SN697 54 55.37 Working Unit - 29K Count

Data corresponds with Stuart's data. Even OSEM SN674 shows a lower voltage reading that is consistant with the low count reading from MEDM.

Looked at the bad OSEM with the short. The short is coming from the Photodiode Cathode side.
Also, we connected and disconnected various OSEMs and don't seem to be having the issue of blowing up the Opamps. Still not sure how the first set of Opamps went bad.